Upload
kimberleywil
View
227
Download
0
Embed Size (px)
Citation preview
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 1/95
]clmw{|dclicb
K`fu}|mw
@umwd|icb [y{|mf{
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 2/95
Bm| |am Hd|m{| ^mw{i`c `n
\ai{ Wmu`w|$
Khiko Amwm \` L`rch`dl |am Hd|m{|
^mw{i`c `n |ai{ Wmu`w|$
\` Fdom [}wm Y`} Dhrdy{ Bm| \am F`{| ]u&\`&Ld|m
Icn`wfd|i`c( Rm Ad~m Kwmd|ml @}w @rc ]uld|m [mw~mw#
Uhmd{m L`rch`dl \am K}wwmc| ^mw{i`c @n \am Wmu`w| Nw`f
Amwm$ \adco{$
7
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 3/95
\` U}wkad{m Uwi~d|m Hdgmh Wiba|{ |`
\ai{ Wmu`w|( Uhmd{m Khiko Amwm
\` Bm| F`wm Uwi~d|m Hdgmh K`c|mc| ( Uhmd{m
^i{i| `}w UHW [|`wm
\dghm `n K`c|mc|{
\dghm `n K`c|mc|{ ################################################################################################################# ;
IC\W@L]K\I@C ############################################################################################################### =
RAD\ I[ DC @UMWD\ICB [Y[\MF0 ############################################################################ 2
AI[\@WY @N @UMWD\ICB [Y[\MF[ ######################################################################### 44
RAD\ DC @UMWD\ICB [Y[\MF L@M[ ##################################################################### 4=
Uw`km{{ Fdcdbmfmc| ##################################################################################################### 4=
Fmf`wy Fdcdbmfmc| #################################################################################################### 77
Li{o dcl Nihm [y{|mf{ ####################################################################################################7=
Cm|r`woicb #################################################################################################################### 7>
[mk}wi|y ########################################################################################################################## 72
Ic|mwcdh [mk}wi|y ############################################################################################################# 79
Mq|mwcdh [mk}wi|y ############################################################################################################;5
Bwduaikdh ]{mw Ic|mwndkm{ ############################################################################################## ;4
;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 4/95
Lm~ikm Lwi~mw{ ############################################################################################################### ;4
Duuhikd|i`c Ic|mwndkm ##################################################################################################### ;;
FIKW@[@N\ RICL@R[ ################################################################################################ ;>
FDK @[ ############################################################################################################################ <2
]CIQ ##################################################################################################################################=;
HIC]Q ############################################################################################################################### =>
BC] ################################################################################################################################### =9
@\AMW @UMWD\ICB [Y[\MF[ ################################################################################### >4
IC[\DHHICB DC @UMWD\ICB [Y[\MF #################################################################### ><
LMNICICB \AM UW@KM[[M[ ######################################################################################### >2
Kdkam ##############################################################################################################################>2
^iw|}dh Fmf`wy ############################################################################################################# 2>
[y{|mf Wm{`}wkm{
######################################################################################################################################## 21
WDF
######################################################################################################################################## 29
K`fu}|mw Fmf`wy
######################################################################################################################################## 1>
K@CKH][I@C ##################################################################################################################97
<
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 5/95
\` U}wkad{m Uwi~d|m Hdgmh Wiba|{ |`\ai{ Wmu`w|( Uhmd{m Khiko Amwm
\` Bm| F`wm Uwi~d|m Hdgmh K`c|mc| ( Uhmd{m
^i{i| `}w UHW [|`wm
IC\W@L]K\I@C
@}w g`ly k`}hlc’| n}ck|i`c ri|a`}| }w gwdic{# \am gwdic |mhh{
|am ~dwi`}{ uimkm{ `n `}w g`ly a`r |` r`wo dcl a`r |` ic|mwdk|#
Ri|a`}| d gwdic( rm r`}hlc’| gm dghm |` l` dcy|aicb d| dhh#
Dc `umwd|icb {y{|mf i{ oicl `n hiom |am gwdic `n d k`fu}|mw # Y`}
ad~m d g}cka `n adwlrdwm hiom |am KU] |`rmw( |am f`ci|`w( dcl |am
omyg`dwl( g}| ri|a`}| d KU]( |amy kdc’| l` dcy|aicb g}| u`rmw }u dcl
|}wc `c# \am `umwd|icb {y{|mf `wbdcizm{ nihm{ dcl hm|{ |am adwlrdwm
oc`r rad| i| {a`}hl l`#
Ic |am mdwhy ldy{ `n k`fu}|mw{( |amwm rd{ j}{| `cm `umwd|icb
{y{|mf# D{ k`fu}|mw{ uw`bwm{{ml( |am @[ |}wcml ic|` F[&L@[( g}|
=
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 6/95
k`fu}|mw{ wmdhhy rmwmc’| kdudghm `n l`icb f}ka ri|a`}| {`n|rdwm#
\amc Gihh Bd|m{ kdfm dh`cb#
Ri|a |am n`}clicb `n Fikw`{`n|( |am k`fu}|mw `umwd|icb {y{|mf
kdfm ic|` i|{ `rc dcl gw`}ba| k`fu}|mw{ |` cmr hm~mh{ `n n}ck|i`cicb
dcl |mkac`h`by# Dh|a`}ba |am gwdcl cdfm{ `n `umwd|icb {y{|mf{ dwm
nmr( |amy l` umwn`wf linnmwmc| |d{o{ lmumclicb `c |am wmt}iwmfmc|{ `n
|am k`fu}|mw }{mw#
Raihm |am l`ficdc| @[ |`ldy r`}hl gm Fikw`{`n| Ricl`r{( |amwm
dwm `|amw |yum{ `n `umwd|icb {y{|mf{ |ad| `nnmw linnmwmc| nmd|}wm{#
\a`{m r`}hl ickh}lm Hic}q( ]CIQ( dcl @[ Q#
Ic `}w |mkac`h`bikdh dbm( |amwm dwm `umwd|icb {y{|mf{ ic f`wm
|adc j}{| k`fu}|mw{# Fdcy `n |am {`uai{|ikd|ml cmr kmhh ua`cm{ ad~m
|amiw `rc `umwd|icb {y{|mf{( dcl riwmhm{{ dkkm{{ u`ic|{ ad~m |amiw
`rc @[ |` uw`~ilm riwmhm{{ ic|mwcm| |` k}{|`fmw{# Ic ndk|( |am
k`fu}|mw ic d kmhh ua`cm |`ldy i{ f`wm u`rmwn}h |adc d k`fu}|mw rd{|rmc|y ymdw{ db`#
D{ y`} kdc {mm( |am `umwd|icb {y{|mf |mkac`h`by ad{ m~`h~ml
dcl i{ k`c|ic}icb |` m~`h~m# I| {mmf{ hiom Fikw`{`n| i{ dhrdy{ k`ficb
`}| ri|a d cmr dcl gm||mw `umwd|icb {y{|mf raika hmdl{ um`uhm |`
r`clmw ram|amw `w c`| |am {y{|mf |amy dwm k}wwmc|hy }{icb i{ wmdhhy
|am gm{| `cm#
I| kdc gm k`cn}{icb# G}| i| l`m{c’| ad~m |` gm# Ic |am udbm{ `n
|ai{ g``o( rm’hh mquh`wm `umwd|icb {y{|mf ic lmu|a# Y`}’hh hmdwc dg`}|
rad| |amy l`( a`r |amy r`wo( dcl rad| cmml{ {umkinik {y{|mf{ kdc
>
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 7/95
fmm|# ]h|ifd|mhy( |am ka`ikm i{ d fd||mw `n uwmnmwmckm( g}| i| amhu{ |`
gm icn`wfml `c rad| y`} dwm wmdhhy bm||icb ramc ka``{icb dc @[#
RAD\ I[ DC @UMWD\ICB [Y[\MF0
Dc `umwd|icb {y{|mf ‛ k`ff`chy wmnmwwml |` d{ dc @[ ‛ i{ d {m|
`n k`fu}|mw uw`bwdf{ |ad| fdcdbm |am adwlrdwm dcl {`n|rdwm
wm{`}wkm{ `n d k`fu}|mw# \am @[ uw km{{m{ mhmk|w`cik lm~ikm{ ri|a d
wd|i`cdh wm{u`c{m |` k`ffdcl{ |ad| dwm duuw`~ml gy |am {y{|mf#
D| |am n`}cld|i`c `n dhh {y{|mf {`n|rdwm( dc `umwd|icb {y{|mf
umwn`wf{ gd{ik |d{o{ hiom k`c|w`hhicb dcl dhh`kd|icb fmf`wy(
uwi`wi|izicb {y{|mf wmt}m{|{( k`c|w`hhicb icu}| dcl `}|u}| lm~ikm{(
ndkihi|d|icb |am cm|r`wo( dcl fdcdbicb nihm{# \am @[ kdc dh{` uw`~ilm
d bwduaikdh }{mw ic|mwndkm n`w aibamw n}ck|i`c{# M{{mc|idhhy( |am @[
n`wf{ d uhd|n`wf n`w `|amw {y{|mf {`n|rdwm d{ rmhh d{ duuhikd|i`c
{`n|rdwm#
2
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 8/95
\am `umwd|icb {y{|mf i{ |am f`{| ifu`w|dc| uw`bwdf |ad| w}c{
`c d k`fu}|mw# Ri|a`}| dc `umwd|icb {y{|mf( y`}w k`fu}|mw r`}hl
c`| r`wo# I| r`}hl c`| gm dghm |` uw`km{{ wmt}m{|{ n`w uwic|( {ifuhm
kdhk}hd|i`c{( `w dcy `|amw n}ck|i`c# I| i{ wmdhhy |am gwdic |ad| w}c{ |am
mt}iufmc|#
N`w hdwbmw {y{|mf( |am @[ ad{ bwmd| wm{u`c{igihi|im{ |adc ri|a d
UK# Ic hdwbmw {y{|mf{( |am `umwd|icb {y{|mf i{ oicl `n hiom d |wdnnik
k`u# I| fdom{ {}wm |ad| linnmwmc| }{mw{ dcl uw`bwdf{ w}ccicb d| |am
{dfm |ifm `c linnmwmc| {y{|mf{ l`c’| ic|mwnmwm ri|a mdka `|amw# I| dh{`
dk|{ d{ d {mk}wi|y b}dwl fdoicb {}wm |ad| }cd}|a`wizml }{mw{ dwm c`|
dghm |` dkkm{{ |am {y{|mf#
\amwm dwm n`}w khd{{inikd|i`c{ `n d k`fu}|mw `umwd|icb {y{|mf#
\amy dwm:
‧
F}h|i&]{mw: Dhh`r{ |r` `w f`wm }{mw{ |` w}c uw`bwdf{ d| |am{dfm |ifm# [`fm `umwd|icb {y{|mf{ umwfi| a}clwml{ `w m~mc
|a`}{dcl{ `n k`ck}wwmc| }{mw{
‧ F}h|i&Uw`km{{icb: [}uu`w|{ w}ccicb d uw`bwdf `c f`wm |adc
`cm KU]
‧ F}h|i&\d{oicb: Dhh`r{ f`wm |adc `cm uw`bwdf |` w}c
k`ck}wwmc|hy
‧ F}h|i&\awmdlicb: Dhh`r{ linnmwmc| udw|{ `n d {icbhm uw`bwdf |`
w}c k`ck}wwmc|hy
1
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 9/95
‧ Wmdh \ifm: Wm{u`cl{ |` icu}| ic{|dc|hy# Bmcmwdh&u}wu`{m
`umwd|icb {y{|mf{( {}ka d{ L@[ dcl ]CIQ( dwm c`| wmdh&|ifm#
@umwd|icb {y{|mf{ uw`~ilm d {`n|rdwm uhd|n`wf `c |`u `n raika
`|amw uw`bwdf{( kdhhml duuhikd|i`c uw`bwdf{ ( kdc w}c# \am duuhikd|i`c
uw`bwdf{ f}{| gm rwi||mc |` w}c `c |`u `n d udw|ik}hdw `umwd|icb
{y{|mf#
Y`}w ka`ikm `n `umwd|icb {y{|mf( |amwmn`wm( lm|mwficm{ |` d
bwmd| mq|mc| |am duuhikd|i`c{ y`} kdc w}c# N`w UK{( |am f`{| u`u}hdw
`umwd|icb {y{|mf{ dwm L@[( @[/7( dcl Ricl`r{( g}| `|amw{ dwm
d~dihdghm( {}ka d{ Hic}q#
Ic dcy lm~ikm |ad| ad{ dc `umwd|icb {y{|mf( |amwm"{ }{}dhhy d
rdy |` fdom kadcbm{ |` a`r |am lm~ikm r`wo{# \ai{ i{ ndw nw`f d
aduuy dkkilmc|? `cm `n |am wmd{`c{ `umwd|icb {y{|mf{ dwm fdlm `}| `n
u`w|dghm k`lm wd|amw |adc umwfdcmc| uay{ikdh kiwk}i|{ i{ {` |ad| |amy
kdc gm kadcbml `w f`liniml ri|a`}| ad~icb |` {kwdu |am ra`hm lm~ikm#
N`w d lm{o|`u k`fu}|mw }{mw( |ai{ fmdc{ y`} kdc dll d cmr
{mk}wi|y }uld|m( {y{|mf ud|ka( cmr duuhikd|i`c `w `n|mc m~mc d cmr
`umwd|icb {y{|mf mc|iwmhy wd|amw |adc j}co y`}w k`fu}|mw dcl {|dw|
dbdic ri|a d cmr `cm ramc y`} cmml |` fdom d kadcbm#
D{ h`cb d{ y`} }clmw{|dcl a`r dc `umwd|icb {y{|mf r`wo{ dcl
oc`r a`r |` bm| d| i|( y`} kdc ic fdcy kd{m{ kadcbm {`fm `n |am
rdy{ i| gmad~m{# Dcl( i|"{ d{ |w}m `n y`}w kmhh ua`cm d{ i| i{ `n y`}w
k`fu}|mw#
[`( m{{mc|idhhy( ramc y`} |}wc `c y`}w k`fu}|mw( |am niw{|
uw`bwdf i{ d {m| `n ic{|w}k|i`c{ omu| ic |am k`fu}|mw’{ wmdl `chy
9
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 10/95
fmf`wy# \am{m ic{|w}k|i`c{ mqdficm |am {y{|mf adwlrdwm |` fdom
{}wm m~mwy|aicb i{ n}ck|i`cicb uw`umwhy# \ai{ u`rmw&`c {mhn |m{| kamko
|am KU]( |am fmf`wy( dcl |am gd{ik icu}|/`}|u}| {y{|mf{ !GI@[) n`w
mww`w{ dcl {|`wm{ |am wm{}h| ic d {umkidh fmf`wy h`kd|i`c#
@ckm |am |m{| ad{ {}kkm{{n}hhy k`fuhm|ml( |am {`n|rdwm h`dlml ic
W@F !{`fm|ifm{ kdhhml |am GI@[ `w niwfrdwm) rihh gmbic |` dk|i~d|m
|am k`fu}|mw"{ li{o lwi~m{# Ic f`{| f`lmwc k`fu}|mw{( ramc |am
k`fu}|mw dk|i~d|m{ |am adwl li{o lwi~m( i| nicl{ |am niw{| uimkm `n |am
`umwd|icb {y{|mf: |am g``|{|wdu h`dlmw#
\am g``|{|wdu h`dlmw i{ d {fdhh uw`bwdf |ad| ad{ d {icbhm
n}ck|i`c: I| h`dl{ |am `umwd|icb {y{|mf ic|` fmf`wy dcl dhh`r{ i| |`
gmbic `umwd|i`c# Ic |am f`{| gd{ik n`wf( |am g``|{|wdu h`dlmw {m|{ }u
|am {fdhh lwi~mw uw`bwdf{ |ad| ic|mwndkm ri|a dcl k`c|w`h |am ~dwi`}{
adwlrdwm {}g{y{|mf{ `n |am k`fu}|mw#
I| {m|{ }u |am li~i{i`c{ `n fmf`wy |ad| a`hl |am `umwd|icb
{y{|mf( }{mw icn`wfd|i`c dcl duuhikd|i`c{# I| m{|dghi{am{ |am ld|d
{|w}k|}wm{ |ad| rihh a`hl |am fywidl {ibcdh{( nhdb{ dcl {mfdua`wm{ |ad|
dwm }{ml |` k`ff}cikd|m ri|aic dcl gm|rmmc |am {}g{y{|mf{ dcl
duuhikd|i`c{ `n |am k`fu}|mw# \amc i| |}wc{ k`c|w`h `n |am k`fu}|mw
`~mw |` |am `umwd|icb {y{|mf#
I| fiba| gm amhun}h n`w y`} |` oc`r |am ai{|`wy `n `umwd|icb
{y{|mf{#
45
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 11/95
AI[\@WY @N @UMWD\ICB [Y[\MF[
\am mdwhim{| `n k`fu}|mw{ lilc’| ad~m dc `umwd|icb {y{|mf# Gy
|am mdwhy 49>5’{( k`ffmwkidh k`fu}|mw ~mcl`w{ rmwm {}uuhyicb t}i|m
mq|mc{i~m |``h{ n`w {|wmdfhicicb |am lm~mh`ufmc|( {kaml}hicb dcl
mqmk}|i`c `n j`g{ `c gd|ka uw`km{{icb {y{|mf{#
\aw`}ba |am 49>5’{( {m~mwdh k`ckmu|{ rmwm lm~mh`uml raika
lw`~m |am lm~mh`ufmc| `n `umwd|icb {y{|mf{# \am IGF [y{|mf ;>5
uw`l}kml d ndfihy `n fdicnwdfm k`fu}|mw |ad| {mw~ml k`c{}fmw{ ri|a
linnmwicb kdudki|im{ dcl uwikm{# D {icbhm `umwd|icb {y{|mf rd{ uhdccml
n`w |am{m k`fu}|mw{ wd|amw |adc lm~mh`uicb bmcmwik uw`bwdf{ n`w
m~mwy icli~il}dh f`lmh#
\ai{ k`ckmu| `n d {icbhm @[ |ad| rihh ni| dc mc|iwm uw`l}k| hicm rd{
kw}kidh n`w |am {}kkm{{ `n [y{|mf ;>5# Ic ndk|( IGF’{ k}wwmc|
fdicnwdfm `umwd|icb {y{|mf{ dwm li{|dc| wmhd|i~m{ `n |ai{ `wibicdh
{y{|mf# \am dl~dc|dbm | |ai{ i{ |ad| duuhikd|i`c{ rwi||mc n`w |am @[
;>5 kdc {|ihh gm w}c `c f`lmwc fdkaicm{#
44
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 12/95
\am @[ ;>5 {y{|mf dh{` k`c|dicml dc`|amw ifu`w|dc| dl~dckm
dnnmk|icb |`ldy’{ k`fu}|mw{: |am lm~mh`ufmc| n d adwl li{o
umwfdcmc| {|`wdbm lm~ikm raika IGF kdhhml LD[L#
D {mk`cl omy lm~mh`ufmc| rd{ |am k`ckmu| `n |ifm {adwicb#
\ifm {adwicb ic~`h~m{ {adwicb |am wm{`}wkm{ `n mqumc{i~m k`fu}|mw{
df`cb f}h|iuhm k`fu}|mw }{mw{ ic|mwdk|icb ic wmdh |ifm ri|a |am
{y{|mf# Rad| |ad| m{{mc|idhhy fmdc{ i{ |ad| dhh `n |am }{mw{ ad~m |am
ihh}{i`c `n mqkh}{i~m dkkm{{ |` |am fdkaicm# \am f`{| ndf`}{ `n |ifm
{adwicb {y{|mf rd{ kdhhml F}h|ik{#
F}h|ik{ {mw~ml d{ dc ic{uiwd|i`c |` d c}fgmw `n `umwd|icb
{y{|mf{ lm~mh`uml ic |am 4925’{# F`{| c`|dghy rd{ |am ]ciq {y{|mf#
Dc`|amw k`ffmwkidhhy u`u}hdw fici&k`fu}|mw `umwd|icb {y{|mf rd{
^F[#
\am niw{| fikw`k`fu}|mw{ lil c`| ad~m |am kdudki|y `w cmml n`w|am mhdg`wd|m `umwd|icb {y{|mf{ |ad| adl `wibicdhhy gmmc lm~mh`uml n`w
fdicnwdfm{ dcl fici{# [fdhhmw `umwd|icb {y{|mf{ rmwm lm~mh`uml
dcl `n|mc h`dlml nw`f W@F dcl oc`rc d{ F`ci|`w{#
@cm c`|dghm mdwhy li{o&gd{ml @[ rd{ KU/F raika rd{ {}uu`w|ml
`c fdcy mdwhy fikw`&k`fu}|mw{ dcl rd{ hdwbmhy kh`cml ramc F[&L@[
rd{ kwmd|ml# F[&L@[ gmkdfm rihlhy u`u}hdw d{ |am `umwd|icb {y{|mfka`{mc n`w |am IGF UK#
\am {}kkm{{i~m `umwd|icb {y{|mf{ |ad| kdfm nw`f F[&L@[ fdlm
Fikw`{`n| `cm `n |am f`{| uw`ni|dghm k`fudcim{ ic |am r`whl ri|a |am
47
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 13/95
lm~mh`ufmc| `n Ricl`r{# \am `chy |amw dh|mwcd|i~m |aw`}ba`}| |am
4915’{ rd{ Fdk @[ raika rd{ |iml ic|ifd|mhy |` |am Duuhm FkIc|`{a
k`fu}|mw#
Gy |am 4995{( |am fikw`k`fu}|mw adl m~`h~ml |` |am u`ic| ramwm
i| gmkdfm ickwmd{icbhy lm{iwdghm# M~mwy`cm rdc|ml d a`fm k`fu}|mw#
Fikw`{`n| adl dhwmdly k`fm `}| ri|a Ricl`r{ 9= dcl 91( g}| um`uhm
h`cbml n`w f`wm u`rmw dcl f`wm `u|i`c{# Fikw`{`n|’{ wm{u`c{m |` |ai{
kadcbm rd{ |am lm~mh`ufmc| `n Ricl`r{ C\ raika {mw~ml d{ |am gd{i{
n`w Fikw`{`n|’{ lm{o|`u `umwd|icb {y{|mf hicm |ad| hd}ckaml ic 7554#
Duuhm rd{ dh{` wmg}ihlicb |amiw `rc `umwd|icb {y{|mf `c |`u `n
]ciq k`wm d{ Fdk @[ Q dh{` wmhmd{ml ic 7554 lm~mh`uicb `cm `n |am
g}{icm{{ r`whl’{ bwmd|m{| wi~dhwim{#
\`ldy( `}w `umwd|icb {y{|mf{ }{}dhhy ad~m d bwduaikdh }{mw
ic|mwndkm !B]I) raika }{m{ d u`ic|icb lm~ikm {}ka d{ d f`}{m `n {|yh}{
n`w icu}| ic dlli|i`c |` |am omyg`dwl# @hlmw {y{|mf{ ‛ dcl rm fmdcWMDHHY @HL ‛ }{m d k`ffdcl hicm ic|mwndkm d{oicb n`w k`ffdcl{ |`
gm mc|mwml ~id |am omyg`dwl#
G`|a f`lmh{ dwm kmc|mwml `c d ‘{amhh‖ raika dkkmu|{ dcl
uw`km{{m{ k`ffdcl{ nw`f |am }{mw# \am }{mw fdy gm d{oml |` khiko
`c d g}||`c `w |yum ic d k`ffdcl }u`c dc `c&{kwmmc uw`fu|#
Gy ndw( |am f`{| k`ff`c `umwd|icb {y{|mf ic }{m |`ldy i{
Ricl`r{ QU( g}| Fikw`{`n| ad{ j}{| wmhmd{ml |amiw cmrm{| Ricl`r{
uw`jmk| ‛ Ricl`r{ ^i{|d# Hic}q i{ dh{` dc`|amw u`u}hdw @[ d{ i{ ]ciq#
4;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 14/95
Rm’hh mquh`wm |amf hd|mw `c ic |am g``o( g}| mdka `nnmw{ i|{ `rc
udw|ik}hdw dl~dc|dbm{ dcl li{dl~dc|dbm{#
K`c{ilmwicb |am g``f `n |am |mkac`h`by fdwom|( i|’{ wmdhhy d
{}wuwi{m |ad| |amwm dwm {` nmr `umwd|icb {y{|mf{ ic mqi{|mckm# \amwm
wmdhhy i{c’| dc md{y mquhdcd|i`c n`w |ai{( g}| i| i{ d wmdhi|y# I| r`}hl
`chy {mmf h`bikdh |ad| ri|a dhh `n |am linnmwmc| k`fu}|mw fdc}ndk|}wmw{
`}| |amwm( |amwm r`}hl gm f`wm `n d ka`ikm n`w dc @[ |adc rad| |amwm
i{# I| i{ kmw|dichy dc |amw dc`fdhy ic |am r`whl `n k`fu}|mw
|mkac`h`by#
[` rad| mqdk|hy l` `umwd|icb {y{|mf{ l`0 [ickm |amy wmdhhy dwm
|am ‘gwdic‖ `n |am k`fu}|mw( |amy l` t}i|m d gi|$
4<
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 15/95
RAD\ DC @UMWD\ICB [Y[\MF L@M[
D{ d }{mw( y`} c`wfdhhy ic|mwdk| ri|a |am `umwd|icb {y{|mf
|aw`}ba d {m| `n k`ffdcl{# N`w mqdfuhm( |am L@[ `umwd|icb {y{|mf
k`c|dic{ k`ffdcl{ {}ka d{ K@UY dcl WMCDFM n`w k`uyicb nihm{ dcl
kadcbicb |am cdfm{ `n nihm{( wm{umk|i~mhy#
\am k`ffdcl{ dwm dkkmu|ml dcl mqmk}|ml gy d udw| `n |am
`umwd|icb {y{|mf kdhhml |am k`ffdcl uw`km{{`w `w k`ffdcl hicm
ic|mwuwm|mw# Bwduaikdh }{mw ic|mwndkm{ dhh`r y`} |` mc|mw k`ffdcl{ gyu`ic|icb dcl khikoicb d| `gjmk|{ |ad| duumdw `c |am {kwmmc#
G}| |ad| wmdhhy l`m{c’| dllwm{{ |am ~dwi`}{ rdy{ |ad| `umwd|icb
{y{|mf{ fdom y`}w k`fu}|mw r`wo md{imw dcl f`wm mnnikimc|hy# \amiw
{umkinik kdudki|im{ dwm rad| fdom |amf amhu y`}w k`fu}|mw `umwd|m d{
d }{mw&nwimclhy lm~ikm# Hm|’{ h``o {umkinikdhhy d| rad| dc `umwd|icb
{y{|mf l`m{#
Uw`km{{ Fdcdbmfmc|
4=
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 16/95
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 17/95
i{ rdi|icb n`w |am KU]#
I|"{ |mfu|icb |` |aico `n d uw`km{{ d{ dc duuhikd|i`c( g}| |ad|
bi~m{ dc ick`fuhm|m uik|}wm `n a`r uw`km{{m{ wmhd|m |` |am `umwd|icb
{y{|mf dcl adwlrdwm# \am duuhikd|i`c y`} {mm !r`wl uw`km{{`w(
{uwmdl{amm| `w bdfm) i{( iclmml( d uw`km{{( g}| |ad| duuhikd|i`c fdy
kd}{m {m~mwdh `|amw uw`km{{m{ |` gmbic( n`w |d{o{ hiom k`ff}cikd|i`c{
ri|a `|amw lm~ikm{ `w `|amw k`fu}|mw{#
\amwm dwm dh{` c}fmw`}{ uw`km{{m{ |ad| w}c ri|a`}| bi~icb y`}
liwmk| m~ilmckm |ad| |amy m~mw mqi{|# N`w mqdfuhm( Ricl`r{ QU dcl
]CIQ kdc ad~m l`zmc{ `n gdkobw`}cl uw`km{{m{ w}ccicb |` adclhm |am
cm|r`wo( fmf`wy fdcdbmfmc|( li{o fdcdbmfmc|( ~iw}{ kamkoicb dcl
{` `c#
D uw`km{{( |amc( i{ {`n|rdwm |ad| umwn`wf{ {`fm dk|i`c dcl kdc
gm k`c|w`hhml && gy d }{mw( gy `|amw duuhikd|i`c{ `w gy |am `umwd|icb
{y{|mf#
I| i{ uw`km{{m{( wd|amw |adc duuhikd|i`c{( |ad| |am `umwd|icb
{y{|mf k`c|w`h{ dcl {kaml}hm{ n`w mqmk}|i`c gy |am KU]# Ic d {icbhm&
|d{oicb {y{|mf( |am {kaml}hm i{ {|wdiba|n`wrdwl# \am `umwd|icb {y{|mf
dhh`r{ |am duuhikd|i`c |` gmbic w}ccicb( {}{umclicb |am mqmk}|i`c `chy
h`cb mc`}ba |` lmdh ri|a ic|mww}u|{ dcl }{mw icu}|#
Ic|mww}u|{ dwm {umkidh {ibcdh{ {mc| gy adwlrdwm `w {`n|rdwm |`
|am KU]# I|"{ d{ in {`fm udw| `n |am k`fu}|mw {}llmchy wdi{ml i|{ adcl
|` d{o n`w |am KU]"{ d||mc|i`c ic d hi~mhy fmm|icb# [`fm|ifm{ |am
`umwd|icb {y{|mf rihh {kaml}hm |am uwi`wi|y `n uw`km{{m{ {` |ad|
ic|mww}u|{ dwm fd{oml && |ad| i{( |am `umwd|icb {y{|mf rihh ibc`wm |am
42
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 18/95
ic|mww}u|{ nw`f {`fm {`}wkm{ {` |ad| d udw|ik}hdw j`g kdc gm nici{aml
d{ t}ikohy d{ u`{{ighm#
\amwm dwm {`fm ic|mww}u|{ {}ka d{ |a`{m nw`f mww`w k`cli|i`c{ `w
uw`ghmf{ ri|a fmf`wy |ad| dwm {` ifu`w|dc| |ad| |amy kdc"| gm
ibc`wml# \am{m c`c&fd{odghm ic|mww}u|{ !CFI{) f}{| gm lmdh| ri|a
iffmlid|mhy( wmbdwlhm{{ `n |am `|amw |d{o{ d| adcl#
Raihm ic|mww}u|{ dll {`fm k`fuhikd|i`c |` |am mqmk}|i`c `n
uw`km{{m{ ic d {icbhm&|d{oicb {y{|mf( |am j`g `n |am `umwd|icb {y{|mf
gmk`fm{ f}ka f`wm k`fuhikd|ml ic d f}h|i&|d{oicb {y{|mf# C`r( |am
`umwd|icb {y{|mf f}{| dwwdcbm |am mqmk}|i`c `n duuhikd|i`c{ {` |ad|
y`} gmhim~m |ad| |amwm dwm {m~mwdh |aicb{ aduumcicb d| `ckm#
\ai{ i{ k`fuhikd|ml gmkd}{m |am KU] kdc `chy l` `cm |aicb d| d
|ifm# Ic `wlmw |` bi~m |am duumdwdckm `n h`|{ `n |aicb{ aduumcicb d|
|am {dfm |ifm( |am `umwd|icb {y{|mf ad{ |` {ri|ka gm|rmmc linnmwmc|uw`km{{m{ |a`}{dcl{ `n |ifm{ d {mk`cl# Amwm"{ a`r i| aduumc{:
‧ D uw`km{{ `kk}uim{ d kmw|dic df`}c| `n WDF# I| dh{` fdom{
}{m `n wmbi{|mw{( {|dko{ dcl t}m}m{ ri|aic |am KU] dcl `umwd|icb&
{y{|mf fmf`wy {udkm#
‧ Ramc |r` uw`km{{m{ dwm f}h|i&|d{oicb( |am `umwd|icb {y{|mf
dhh`|{ d kmw|dic c}fgmw `n KU] mqmk}|i`c kykhm{ |` `cm uw`bwdf#
‧ Dn|mw |ad| c}fgmw `n kykhm{( |am `umwd|icb {y{|mf fdom{
k`uim{ `n dhh |am wmbi{|mw{( {|dko{ dcl t}m}m{ }{ml gy |am uw`km{{m{
41
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 19/95
dcl c`|m |am u`ic| d| raika |am uw`km{{ ud}{ml ic i|{ mqmk}|i`c#
‧ I| |amc h`dl{ dhh |am wmbi{|mw{( {|dko{ dcl t}m}m{ }{ml gy |am
{mk`cl uw`km{{ dcl dhh`r i| d kmw|dic c}fgmw `n KU] kykhm{#
‧ Ramc |a`{m dwm k`fuhm|m( i| fdom{ k`uim{ `n dhh |am wmbi{|mw{(
{|dko{ dcl t}m}m{ }{ml gy |am {mk`cl uw`bwdf( dcl h`dl |am niw{|
uw`bwdf#
Dhh `n |am icn`wfd|i`c cmmlml |` ommu |wdko `n d uw`km{{ ramc
{ri|kaicb i{ omu| ic d ld|d udkodbm kdhhml d uw`km{{ k`c|w`h gh`ko# \am
uw`km{{ k`c|w`h gh`ko |yuikdhhy k`c|dic{:
‧ Dc IL c}fgmw |ad| ilmc|inim{ |am uw`km{{
‧ U`ic|mw{ |` |am h`kd|i`c{ ic |am uw`bwdf dcl i|{ ld|d ramwm
uw`km{{icb hd{| `kk}wwml
‧ Wmbi{|mw k`c|mc|{
‧ [|d|m{ `n ~dwi`}{ nhdb{ dcl {ri|kam{
‧ U`ic|mw{ |` |am }uumw dcl h`rmw g`}cl{ `n |am fmf`wy
wmt}iwml n`w |am uw`km{{
‧ D hi{| `n nihm{ `umcml gy |am uw`km{{
‧ \am uwi`wi|y `n |am uw`km{{
49
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 20/95
‧ \am {|d|}{ `n dhh I/@ lm~ikm{ cmmlml gy |am uw`km{{
Mdka uw`km{{ ad{ d {|d|}{ d{{`kid|ml ri|a i|# Fdcy uw`km{{m{
k`c{}fm c` KU] |ifm }c|ih |amy bm| {`fm {`w| `n icu}|# N`w mqdfuhm( d
uw`km{{ fiba| gm rdi|icb `c d omy{|w`om nw`f |am }{mw# Raihm i| i{
rdi|icb n`w |am omy{|w`om( i| }{m{ c` KU] |ifm# Raihm i| i{ rdi|icb( i| i{
‘{}{umclml‖#
Ramc |am omy{|w`om dwwi~m{( |am @[ kadcbm{ i|{ {|d|}{# Ramc
|am {|d|}{ `n |am uw`km{{ kadcbm{( nw`f umclicb |` dk|i~m( n`w
mqdfuhm( `w nw`f {}{umclml |` w}ccicb( |am icn`wfd|i`c ic |am uw`km{{
k`c|w`h gh`ko f}{| gm }{ml hiom |am ld|d ic dcy `|amw uw`bwdf |` liwmk|
mqmk}|i`c `n |am |d{o&{ri|kaicb u`w|i`c `n |am `umwd|icb {y{|mf#
\ai{ uw`km{{ {rduuicb aduumc{ ri|a`}| liwmk| }{mw ic|mwnmwmckm(
dcl mdka uw`km{{ bm|{ mc`}ba KU] kykhm{ |` dkk`fuhi{a i|{ |d{o ic d
wmd{`cdghm df`}c| `n |ifm# \w`}ghm kdc k`fm( |a`}ba( in |am }{mw |wim{
|` ad~m |`` fdcy uw`km{{m{ n}ck|i`cicb d| |am {dfm |ifm# \am
`umwd|icb {y{|mf i|{mhn wmt}iwm{ {`fm KU] kykhm{ |` umwn`wf |am
{d~icb dcl {rduuicb `n dhh |am wmbi{|mw{( t}m}m{ dcl {|dko{ `n |am
duuhikd|i`c uw`km{{m{#
In mc`}ba uw`km{{m{ dwm {|dw|ml( dcl in |am `umwd|icb {y{|mf
ad{c"| gmmc kdwmn}hhy lm{ibcml( |am {y{|mf kdc gmbic |` }{m |am ~d{|
fdj`wi|y `n i|{ d~dihdghm KU] kykhm{ |` {rdu gm|rmmc uw`km{{m{ wd|amw
|adc w}c uw`km{{m{# Ramc |ai{ aduumc{( i|"{ kdhhml |awd{aicb( dcl i|
}{}dhhy wmt}iwm{ {`fm {`w| `n liwmk| }{mw ic|mw~mc|i`c |` {|`u uw`km{{m{
75
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 21/95
dcl gwicb `wlmw gdko |` |am {y{|mf#
@cm rdy |ad| `umwd|icb&{y{|mf lm{ibcmw{ wml}km |am kadckm `n
|awd{aicb i{ gy wml}kicb |am cmml n`w cmr uw`km{{m{ |` umwn`wf
~dwi`}{ |d{o{# [`fm `umwd|icb {y{|mf{ dhh`r n`w d ‘uw`km{{ hi|m‖ kdhhml
d |awmdl |ad| kdc lmdh ri|a dhh |am KU]&ic|mc{i~m r`wo `n d c`wfdh
uw`km{{( g}| bmcmwdhhy l`m{ c`| lmdh ri|a |am ~dwi`}{ |yum{ `n I/@ dcl
l`m{ c`| m{|dghi{a {|w}k|}wm{ wmt}iwicb |am mq|mc{i~m uw`km{{ k`c|w`h
gh`ko `n d wmb}hdw uw`km{{# D uw`km{{ fdy {|dw| fdcy |awmdl{ `w `|amw
uw`km{{m{( g}| d |awmdl kdcc`| {|dw| d uw`km{{#
[` ndw( dhh |am {kaml}hicb rm"~m li{k}{{ml ad{ k`ckmwcml d {icbhm
KU]# Ic d {y{|mf ri|a |r` `w f`wm KU]{( |am `umwd|icb {y{|mf f}{|
li~ilm |am r`woh`dl df`cb |am KU]{( |wyicb |` gdhdckm |am lmfdcl{ `n
|am wmt}iwml uw`km{{m{ ri|a |am d~dihdghm kykhm{ `c |am linnmwmc| KU]{#
D{yffm|wik `umwd|icb {y{|mf{ }{m `cm KU] n`w |amiw `rc cmml{dcl li~ilm duuhikd|i`c uw`km{{m{ df`cb |am wmfdicicb KU]{#
[yffm|wik `umwd|icb {y{|mf{ li~ilm |amf{mh~m{ df`cb |am ~dwi`}{
KU]{( gdhdckicb lmfdcl ~mw{}{ KU] d~dihdgihi|y m~mc ramc |am
`umwd|icb {y{|mf i|{mhn i{ dhh |ad|"{ w}ccicb#
M~mc in |am `umwd|icb {y{|mf i{ |am `chy {`n|rdwm ri|a mqmk}|i`c
cmml{( |am KU] i{ c`| |am `chy wm{`}wkm |` gm {kaml}hml# Fmf`wy
fdcdbmfmc| i{ |am cmq| kw}kidh {|mu ic fdoicb {}wm |ad| dhh uw`km{{m{
w}c {f``|ahy#
74
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 22/95
Fmf`wy Fdcdbmfmc|
\am rdy k`fu}|mw{ dwm g}ih|( |am fmf`wy i{ dwwdcbml ic d
aimwdwkadh rdy# I| {|dw|{ ri|a |am nd{|m{| wmbi{|mw{( |am KU] kdkam(wdcl`f dkkm{{ fmf`wy( dcl li{o {|`wdbm# Dc `umwd|icb {y{|mf’{
fmf`wy fdcdbmw k``wlicd|m{ |am }{m `n |am{m ~dwi`}{ fmf`wy |yum{
gy |wdkoicb raika `cm i{ d~dihdghm( raika `cm {a`}hl gm dhh`kd|ml `w
lm&dhh`kd|ml dcl a`r |` f`~m ld|d gm|rmmc |amf#
\ai{ n}ck|i`c i{ wmnmwwml |` d{ ~iw|}dh fmf`wy fdcdbmfmc| dcl
ickwmd{m{ |am df`}c| `n fmf`wy d~dihdghm n`w mdka uw`km{{ gy fdoicb|am li{o {|`wdbm {mmf hiom fdic fmf`wy# \amwm i{ d {umml umcdh|y
d{{`kid|ml ri|a }{icb li{o{ `w `|amw {h`rmw {|`wdbm d{ fmf`wy# In
w}ccicb uw`km{{m{ wmt}iwm{ {ibcinikdc|hy f`wm WDF |adc i{ d~dihdghm(
|am {y{|mf fdy {|dw| ‘|awd{aicb‖ `w {h`ricb l`rc#
\ai{ kdc aduumc mi|amw gmkd}{m `cm uw`km{{ wmt}iwm{ d hdwbm
df`}c| `n WDF `w gmkd}{m |r` `w f`wm uw`km{{m{ k`fum|m n`w d hdwbmwdf`}c| `n fmf`wy |adc i{ d~dihdghm# \ai{ |amc hmdl{ |` k`c{|dc|
|wdc{nmw `n mdka uw`km{{’{ ld|d |` {h`rmw {|`wdbm#
Dc`|amw ifu`w|dc| udw| `n fmf`wy fdcdbmfmc| i{ fdcdbicb
~iw|}dh dllwm{{m{# In f}h|iuhm uw`km{{m{ dwm ic |am fmf`wy d| |am
{dfm |ifm( |amy f}{| gm {|`uuml nw`f ic|mwnmwicb ri|a mdka `|amw’{
fmf`wy }chm{{ |amwm i{ dc mquhiki| wmt}m{| |` }|ihizm {adwml fmf`wy#\ai{ i{ dkaim~ml gy ad~icb {mudwd|m dllwm{{ {udkm{#
Mdka uw`km{{ {mm{ |am ra`hm ~iw|}dh dllwm{{ {udkm( |yuikdhhy nw`f
dllwm{{ 5 }u |` |am fdqif}f {izm `n ~iw|}dh fmf`wy d{ }cit}mhy
77
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 23/95
d{{ibcml |` i|# \am `umwd|icb {y{|mf fdic|dic{ d udbm |dghm{ |ad|
fd|kam{ ~iw|}dh dllwm{{m{ |` uay{ikdh dllwm{{m{# \am{m fmf wy
dhh`kd|i`c{ dwm |wdkoml {` |ad| ramc d uw`km{{ mcl{( dhh fmf`wy }{ml
gy |ad| uw`km{{ kdc gm fdlm d~dihdghm n`w `|amw uw`km{{m{#
\am `umwd|icb {y{|mf kdc dh{` rwi|m icdk|i~m fmf`wy udbm{ |`
{mk`cldwy {|`wdbm# \ai{ uw`km{{ i{ kdhhml ‘udbicb‖ `w ‘{rduuicb‖# \am
|mwfic`h`by ~dwim{ gm|rmmc `umwd|icb {y{|mf#
I| i{ dh{` |yuikdh n`w `umwd|icb {y{|mf{ |` mfuh`y `|amwri{m
}c}{ml uay{ikdh fmf`wy d{ d udbm kdkam# \am udbm kdkam k`c|dic{
wmt}m{|{ ld|d nw`f d {h`rmw lm~ikm dcl kdc gm wm|dicml ic fmf`wy |`
ifuw`~m umwn`wfdckm# \am @[ kdc dh{` uwm&h`dl |am ic&fmf`wy kdkam
ri|a ld|d |ad| fdy gm wmt}m{|ml gy |am }{mw ic |am cmdw n}|}wm#
\am niw{| |d{o `n fmf`wy fdcdbmfmc| wmt}iwm{ |am `umwd|icb
{y{|mf |` {m| }u fmf`wy g`}cldwim{ n`w |yum{ `n {`n|rdwm dcl n`w
icli~il}dh duuhikd|i`c{#
D{ dc mqdfuhm( hm|"{ h``o d| dc ifdbicdwy {fdhh {y{|mf ri|a 4
fmbdgy|m !4(555 oih`gy|m{) `n WDF# L}wicb |am g``| uw`km{{( |am
`umwd|icb {y{|mf `n `}w ifdbicdwy k`fu}|mw i{ lm{ibcml |` b` |` |am
|`u `n d~dihdghm fmf`wy dcl |amc 'gdko }u' ndw mc`}ba |` fmm| |am
cmml{ `n |am `umwd|icb {y{|mf i|{mhn#
Hm|"{ {dy |ad| |am `umwd|icb {y{|mf cmml{ ;55 oih`gy|m{ |` w}c#
C`r( |am `umwd|icb {y{|mf b`m{ |` |am g`||`f `n |am u``h `n WDF dcl
{|dw|{ g}ihlicb }u ri|a |am ~dwi`}{ lwi~mw {`n|rdwm wmt}iwml |` k`c|w`h
|am adwlrdwm {}g{y{|mf{ `n |am k`fu}|mw# Ic `}w ifdbicdwy k`fu}|mw(
7;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 24/95
|am lwi~mw{ |dom }u 755 oih`gy|m{# [` dn|mw bm||icb |am `umwd|icb
{y{|mf k`fuhm|mhy h`dlml( |amwm dwm =55 oih`gy|m{ wmfdicicb n`w
duuhikd|i`c uw`km{{m{#
Ramc duuhikd|i`c{ gmbic |` gm h`dlml ic|` fmf`wy( |amy dwm
h`dlml ic gh`ko {izm{ lm|mwficml gy |am `umwd|icb {y{|mf# In |am gh`ko
{izm i{ 7 oih`gy|m{( |amc m~mwy uw`km{{ |ad| i{ h`dlml rihh gm bi~mc d
ka}co `n fmf`wy |ad| i{ d f}h|iuhm `n 7 oih`gy|m{ ic {izm# Duuhikd|i`c{
rihh gm h`dlml ic |am{m niqml gh`ko {izm{( ri|a |am gh`ko{ {|dw|icb dcl
mclicb `c g`}cldwim{ m{|dghi{aml gy r`wl{ `n < `w 1 gy|m{#
\am{m gh`ko{ dcl g`}cldwim{ amhu |` mc{}wm |ad| duuhikd|i`c{
r`c"| gm h`dlml `c |`u `n `cm dc`|amw"{ {udkm gy d u``why kdhk}hd|ml
gi| `w |r`# Ri|a |ad| mc{}wml( |am hdwbmw t}m{|i`c i{ rad| |` l` ramc
|am =55&oih`gy|m duuhikd|i`c {udkm i{ nihhml#
Ic f`{| k`fu}|mw{( i|"{ u`{{ighm |` dll fmf`wy gmy`cl |am`wibicdh kdudki|y# N`w mqdfuhm( y`} fiba| mqudcl WDF nw`f 4 |` 7
fmbdgy|m{# \ai{ r`wo{ nicm( g}| |mcl{ |` gm wmhd|i~mhy mqumc{i~m# I|
dh{` ibc`wm{ d n}cldfmc|dh ndk| `n k`fu}|icb && f`{| `n |am
icn`wfd|i`c |ad| dc duuhikd|i`c {|`wm{ ic fmf`wy i{ c`| gmicb }{ml d|
dcy bi~mc f`fmc|#
D uw`km{{`w kdc `chy dkkm{{ fmf`wy `cm h`kd|i`c d| d |ifm( {`
|am ~d{| fdj`wi|y `n WDF i{ }c}{ml d| dcy f`fmc|# [ickm li{o {udkm i{
kamdu k`fudwml |` WDF( |amc f`~icb icn`wfd|i`c ic WDF |` adwl li{o
kdc bwmd|hy mqudcl WDF {udkm d| c` k`{|# \ai{ |mkacit}m i{ kdhhml
7<
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 25/95
~iw|}dh fmf`wy fdcdbmfmc|#
Li{o {|`wdbm i{ `chy `cm `n |am fmf`wy |yum{ |ad| f}{| gm
fdcdbml gy |am `umwd|icb {y{|mf( dcl i{ |am {h`rm{|# Wdcoml ic `wlmw
`n {umml( |am |yum{ `n fmf`wy ic d k`fu}|mw {y{|mf dwm:
‧ Aiba&{umml kdkam & \ai{ i{ nd{|( wmhd|i~mhy {fdhh df`}c|{ `n
fmf`wy |ad| dwm d~dihdghm |` |am KU] |aw`}ba |am nd{|m{|
k`ccmk|i`c{# Kdkam k`c|w`hhmw{ uwmlik| raika uimkm{ `n ld|d |am KU]
rihh cmml cmq| dcl u}hh i| nw`f fdic fmf`wy ic|` aiba&{umml kdkam
|` {umml }u {y{|mf umwn`wfdckm#
‧ Fdic fmf`wy & \ai{ i{ |am WDF |ad| y`} {mm fmd{}wml ic
fmbdgy|m{ ramc y`} g}y d k`fu}|mw#
‧ [mk`cldwy fmf`wy & \ai{ i{ f`{| `n|mc {`fm {`w| `n
w`|d|icb fdbcm|ik {|`wdbm |ad| ommu{ duuhikd|i`c{ dcl ld|d d~dihdghm
|` gm }{ml( dcl {mw~m{ d{ ~iw|}dh WDF }clmw |am k`c|w`h `n |am
`umwd|icb {y{|mf#
\am `umwd|icb {y{|mf f}{| gdhdckm |am cmml{ `n |am ~dwi`}{
uw`km{{m{ ri|a |am d~dihdgihi|y `n |am linnmwmc| |yum{ `n fmf`wy(
f`~icb ld|d ic gh`ko{ !kdhhml udbm{) gm|rmmc d~dihdghm fmf`wy d{ |am
{kaml}hm `n uw`km{{m{ lik|d|m{#
Li{o dcl Nihm [y{|mf{
7=
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 26/95
Dhh `umwd|icb {y{|mf{ ickh}lm {}uu`w| n`w d ~dwim|y `n nihm
{y{|mf{# F`lmwc nihm {y{|mf{ dwm fdlm }u `n liwmk|`wim{# Raihm |am
ilmd i{ {ifihdw ic k`ckmu| dkw`{{ dhh bmcmwdh u}wu`{m nihm {y{|mf{( {`fm
linnmwmckm{ ic ifuhmfmc|d|i`c mqi{|#
\r` mqdfuhm{ `n |ai{ dwm |am kadwdk|mw |ad| i{ }{ml |` {mudwd|m
liwmk|`wim{ dcl kd{m {mc{i|i~i|y# Gy lmnd}h|( Fikw`{`n| Ricl`r{
{mudwd|m{ i|{ ud|a k`fu`cmc|{ ri|a d gdko{hd{a dcl i|{ nihm cdfm{ dwm
c`| kd{m {mc{i|i~m#
A`rm~mw( ]CIQ dcl Hic}q lmwi~ml `umwd|icb {y{|mf{ dh`cb ri|a
Fdk @[ }{m |am n`wrdwl {hd{a dcl |amiw nihm cdfm{ dwm bmcmwdhhy kd{m
{mc{i|i~m# [`fm ~mw{i`c{ `n Fdk @[ !|a`{m uwi`w |` @[ Q) }{m d k`h`w
n`w d ud|a {mudwd|`w#
Nihm {y{|mf{ dwm mi|amw j`}wcdhml `w c`c&j`}wcdhml# D j`}wcdhml
nihm {y{|mf i{ d {dnmw dh|mwcd|i~m ic |am m~mc| `n d {y{|mf kwd{a# In d
{y{|mf k`fm{ |` dc dgw}u| {|`u ic d kwd{a {kmcdwi`( |am c`c&j`}wcdhml{y{|mf rihh cmml | gm mqdficml gy |am {y{|mf kamko }|ihi|im{# @c |am
`|amw adcl( d j`}wcdhml nihm {y{|mf{ wmk`~mwy i{ d}|`fd|ik#
\am nihm {y{|mf{ ~dwy gm|rmmc `umwd|icb {y{|mf{( g}| k`ff`c
|` dhh |am{m i{ {}uu`w| n`w nihm {y{|mf{ |yuikdhhy n`}cl `c wmf`~dghm
fmlid hiom KL{( L^L{( dcl nh`uuy li{o{# \amy dh{` uw`~ilm n`w |am
wmrwi|icb `n KL{ dcl L^L{ d{ {|`wdbm fmli}f{#
Cm|r`woicb
7>
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 27/95
Dc`|amw d{umk| `n dc `umwd|icb {y{|mf ad{ |` l` ri|a |am
cm|r`woicb kdudgihi|im{ k`c|dicml ic mdka# \am cm|r`wo hico{ {mudwd|m
k`fu}|mw{ |`bm|amw nw`f linnmwmc| h`kd|i`c{#
F`{| k}wwmc| `umwd|icb {y{|mf{ dwm kdudghm `n }{icb |am \KU/IU
cm|r`woicb uw`|`k`h{# \ad| fmdc{ |ad| `cm {y{|mf kdc duumdw `c d
cm|r`wo `n |am `|amw dcl {adwm wm{`}wkm{ {}ka d{ nihm{( uwic|mw{( dcl
{kdccmw{ }{icb mi|amw riwml `w riwmhm{{ k`ccmk|i`c{#
[mk}wi|y
[mk}wi|y i{ ifu`w|dc| ic dcy k`fu}|mw {y{|mf# \am `umwd|icb
{y{|mf uw`~ilm{ d hm~mh `n {mk}wi|y |ad| kdc uw`|mk| y`}w k`fu}|mw dcl
|am ld|d `c i|# [y{|mf {mk}wi|y i{ gd{ml `c |r` uwickiuhm{:
‧ \ad| |am `umwd|icb {y{|mf uw`~ilm{ dkkm{{ |` fdcy wm{`}wkm{
mi|amw liwmk|hy `w icliwmk|hy# \ad| k`}hl fmdc nihm{ `c d h`kdhli{o( uwi~ihmbml {y{|mf kdhh{( umw{`c icn`wfd|i`c dg`}| }{mw( dcl
|am {mw~ikm{ `nnmwml gy |am uw`bwdf{ w}ccicb `c |am {y{|mf#
‧ \ad| |am `umwd|icb {y{|mf i{ kdudghm `n li{|icb}i{aicb gm|rmmc
|a`{m ra` dwm dhh`rml |` dkkm{{ |am wm{`}wkm dcl |a`{m ra` dwm
n`wgillmc |` l` {`# Raihm {`fm {y{|mf{ fdy {ifuhy li{|icb}i{a
gm|rmmc ‘uwi~ihmbml‖ dcl ‘c`c&uwi~ihmbml‖( f`{| k`ff`chy ad~md n`wf `n wmbi{|mw ilmc|i|y {}ka d{ d }{mw cdfm#
72
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 28/95
Wmt}m{|mw{ `n icn`wfd|i`c dwm n}w|amw li~ilml ic|` |r`
kd|mb`wim{:
‧ Ic|mwcdh {mk}wi|y ic dc dhwmdly w}ccicb uw`bwdf# @c {`fm
{y{|mf{( `ckm d uw`bwdf i{ w}ccicb( i| ad{ c` hifi|d|i`c{( g}|
k`ff`chy( |am uw`bwdf ad{ dc ilmc|i|y raika i| ommu{# \ad|
ilmc|i|y i{ }{ml |` kamko dhh `n i|{ wmt}m{|{ n`w wm{`}wkm{#
‧ Mq|mwcdh {mk}wi|y d{ ic d cmr wmt}m{| nw`f `}|{ilm |am k`fu}|mw#
\ai{ k`}hl gm ic |am n`wf `n d cmr wmt}m{| nw`f `}|{ilm |am
{y{|mf {}ka d{ d h`bic d| d k`ccmk|ml k`c{`hm `w {`fm oicl `n cm|r`wo k`ccmk|i`c# \` m{|dghi{a ilmc|i|y( |amwm fdy gm d
uw`km{{ `n d}|amc|ikd|i`c#
@n|mc d }{mwcdfm f}{| gm mc|mwml dcl m~mwy }{mwcdfm {a`}hl
ad~m d ud{{r`wl# @|amw fm|a`l{ `n d}|amc|ikd|i`c {}ka d{
fdbcm|ik kdwl{ `w gi`fm|wik ld|d fdy gm }{ml ic{|mdl# Ic {`fm
kd{m{( m{umkidhhy k`ccmk|i`c{ nw`f |am cm|r`wo( wm{`}wkm{ fdygm dkkm{{ml ri|a c` d}|amc|ikd|i`c d| dhh#
Ic dlli|i`c |` |am dhh`r/li{dhh`r f`lmh `n {mk}wi|y( d {y{|mf ri|a
d aiba hm~mh n {mk}wi|y rihh dh{` nnmw d}li|icb `u|i`c{# \am{m r`}hl
dhh`r |wdkoicb `n wmt}m{|{ n`w dkkm{{ |` wm{`}wkm{ d{ ic ‘ra` ad{ gmmc
wmdlicb |ai{ nihm0‖
@umwd|icb {y{|mf {mk}wi|y ad{ h`cb gmmc d k`ckmwc `n
uw`bwdffmw{ gmkd}{m `n aibahy {mc{i|i~m ld|d amhl `c {`fm
k`fu}|mw{# \ai{ i{ g`|a `n d k`ffmwkidh dcl d fihi|dwy cd|}wm#
71
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 29/95
\am ][ B`~mwcfmc| Lmudw|fmc| `n Lmnmc{m kwmd|ml |amiw `rc
kwi|mwid `n {|dcldwl{ |ad| {m|{ gd{ik wmt}iwmfmc| n`w d{{m{{icb |am
mnnmk|i~mcm{{ `n @[ {mk}wi|y# \ai{ gmkdfm `n ~i|dh ifu`w|dckm |`
`umwd|icb {y{|mf fdomw{ gmkd}{m |ai{ {y{|mf rd{ }{ml |` khd{{iny dcl
{mhmk| {y{|mf gmicb k`c{ilmwml n`w |am uw`km{{icb( {|`wdbm dl wm|wim~dh
`n {mc{i|i~m `w khd{{iniml icn`wfd|i`c#
Ic|mwcdh [mk}wi|y
Ic|mwcdh {mk}wi|y kdc gm |a`}ba| `n d{ d rdy |` uw`|mk| |am
k`fu}|mw’{ wm{`}wkm{ nw`f |am uw`bwdf{ k`ck}wwmc|hy w}ccicb `c |am
{y{|mf# F`{| `umwd|icb {y{|mf{ {m| uw`bwdf{ w}ccicb cd|i~mhy `c |am
k`fu}|mw’{ uw`km{{`w# \ad| gwicb{ `c |am uw`ghmf n a`r |` {|`u
|am{m uw`bwdf{ nw`f l`icb |am {dfm |d{o dcl ad~icb |am {dfm
uwi~ihmbm{ d{ |am `umwd|icb {y{|mf raika i{ j}{| d uw`bwdf |``#
Uw`km{{`w{ }{ml n`w bmcmwdh u}wu`{m `umwd|icb {y{|mf{ dwm
d}|`fd|ikdhhy gh`koml nw`f }{icb kmw|dic adwlrdwm ic{|w}k|i`c{ {}ka d{
|a`{m |` wmdl `w rwi|m nw`f mq|mwcdh lm~ikm{ hiom li{o{# Ic{|mdl( |amy
ad~m |` d{o |am uwi~ihmbml uw`bwdf( `w `umwd|icb {y{|mf omwcmh) |`
wmdl |` rwi|m# \am `umwd|icb {y{|mf( |amwmn`wm( bm|{ |am kadckm |`
kamko |am uw`bwdf’{ ilmc|i|y dcl dhh`r `w wmn}{ml |am wmt}m{|#
Dc dh|mwcd|i~m {|wd|mby d~dihdghm ic {y{|mf{ |ad| l`c’| fmm| uwm&
{m| wmt}iwmfmc|{ i{ |am `umwd|icb rihh c`| w}c }{mw uw`bwdf{ d{ cd|i~m
k`lm# Ic{|mdl( |amy mi|amw mf}hd|m d uw`km{{`w `w uw`~ilm d a`{| n`w d
‘u&K`lm‖ gd{ml {y{|mf {}ka d{ Jd~d#
79
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 30/95
Ic|mwcdh {mk}wi|y i{ m{umkidhhy ifu`w|dc| ri|a f}h|i&}{mw {y{|mf{
d{ i| dhh`r{ mdka }{mw `n |am {y{|mf |` ad~m uwi~d|m nihm{ |ad| |am `|amw
}{mw{ kdcc`| |dfumw ri|a `w wmdl# Ic|mwcdh {mk}wi|y i{ dh{` ~i|dh in
d}li|icb i{ |` gm `n dcy }{m {ickm d uw`bwdf kdc u`|mc|idhhy gyud{{ |am
`umwd|icb {y{|mf ri|a`}| gyud{{ d}li|icb#
Mq|mwcdh [mk}wi|y
\yuikdhhy( dc `umwd|icb {y{|mf `nnmw{ ~dwi`}{ {mw~ikm{ |` `|amw
cm|r`wo k`fu}|mw{ dcl }{mw{# \am{m {mw~ikm{ dwm }{}dhhy uw`~ilml
|aw`}ba u`w|{ `w c}fgmwml dkkm{{ u`ic|{ gmy`cl |am `umwd|icb
{y{|mf{ cm|r`wo dllwm{{# \am{m {mw~ikm{ ickh}lm `nnmwicb{ {}ka d{ nihm
{adwicb( uwic| {mw~ikm{( m&fdih( rmg {i|m{( dcl nihm |wdc{nmw uw`|`k`h{
!N\U)#
D| |am nw`c| hicm `n {mk}wi|y dwm adwlrdwm lm~ikm{ oc`rc d{
niwmrdhh{# D| |am `umwd|icb {y{|mf hm~mh( |amwm dwm d c}fgmw `n
{`n|rdwm niwmrdhh{ d~dihdghm# F`{| f`lmwc `umwd|icb {y{|mf{ ickh}lm d
{`n|rdwm niwmrdhh raika i{ mcdghml gy lmnd}h|#
D {`n|rdwm niwmrdhh kdc gm k`cnib}wml |` dhh`r `w lmcy cm|r`wo
|wdnnik |` `w nw`f d {mw~ikm `w duuhikd|i`c w}ccicb `c |am `umwd|icb
{y{|mf# \amwmn`wm( `cm kdc ic{|dhh dcl gm w}ccicb dc ic{mk}wm {mw~ikm
{}ka d{ \mhcm| `w N\U dcl c`| ad~m |` gm |awmd|mcml gy d {mk}wi|y
gwmdka gmkd}{m |am niwmrdhh r`}hl lmcy dhh |wdnnik |wyicb |` k`ccmk| |`
|am {mw~ikm `c |ad| u`w|#
;5
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 31/95
Bwduaikdh ]{mw Ic|mwndkm{
\`ldy( f`{| f`lmwc `umwd|icb {y{|mf{ k`c|dic Bwduaikdh ]{mw
Ic|mwndkm{ !B]I{)# D nmr `n |am `hlmw `cm{ |iba|hy ic|mbwd|ml |am B]I
|` |am omwcmh ‛ `cm `n |am kmc|wdh k`fu`cmc|{ `n |am `umwd|icb {y{|mf#
F`wm f`lmwc `umwd|icb {y{|mf{ dwm f`l}hdw {mudwd|icb |am bwduaik{
{}g{y{|mf nw`f |am omwcmh#
D B]I i{ gd{ikdhhy |am uik|}wm{ y`} {mm `c |am {kwmmc |ad| amhu
y`} cd~ibd|m y`}w k`fu}|mw# \amy ickh}lm |am ik`c{ dcl |am fmc}{#
Fdcy `umwd|icb {y{|mf{ dhh`r |am }{mw |` ic{|dhh `w kwmd|m dcy }{mw
ic|mwndkm |amy lm{iwm#
Bwduaikdh }{mw ic|mwndkm{ |mcl |` kadcbm dcl m~`h~m `~mw |ifm#N`w mqdfuhm( Ricl`r{ ad{ f`liniml i|{ }{mw ic|mwndkm dhf`{| m~mwy
|ifm d cmr ~mw{i`c `n Ricl`r{ i{ wmhmd{ml# \am Fdk @[ B]I kadcbml
lwdfd|ikdhhy ri|a |am ic|w`l}k|i`c `n Fdk @[ Q ic 7554#
Lm~ikm Lwi~mw{
D lm~ikm lwi~mw i{ d {umkinik |yum `n k`fu}|mw {`n|rdwm lm~mh`uml
|` dhh`r ic|mwdk|i`c ri|a adwlrdwm lm~ikm{# \yuikdhhy( |ai{ k`c{|i|}|m{
dc ic|mwndkm n`w k`ff}cikd|icb ri|a |am lm~ikm |aw`}ba |am {umkinik
;4
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 32/95
k`fu}|mw g}{ `w k`ff}cikd|i`c{ {}g{y{|mf |ad| |am adwlrdwm i{
k`ccmk|ml |`#
Lm~ikm lwi~mw{ uw`~ilm k`ffdcl{ |` dcl/`w wmkmi~icb ld|d nw`f
|am lm~ikm dcl `c |am `|amw mcl( |am wmt}i{i|m ic|mwndkm{ |` |am
`umwd|icb {y{|mf dcl {`n|rdwm duuhikd|i`c{#
Y`} kdcc`| ad~m d KL&W@F lwi~m( n`w mqdfuhm( ri|a`}| d lm~ikm
lwi~mw n`w |ad| {umkinik uimkm `n mt}iufmc|# Y`} ad~m lwi~mw{ n`w d
uwic|mw( {kdccmw( dcl m~mc y`}w f`}{m#
I| i{ d {umkidhizml adwlrdwm&lmumclmc| uw`bwdf raika i{ dh{`
`umwd|icb {y{|mf {umkinik |ad| mcdghm{ dc`|amw uw`bwdf ‛ |yuikdhhy dc
`umwd|icb {y{|mf `w duuhikd|i`c{ {`n|rdwm udkodbm `w k`fu}|mw
uw`bwdf w}ccicb }clmw |am `umwd|icb {y{|mf omwcmh#
\ai{ dhh`r{ |am {y{|mf |` ic|mwdk| |wdc{udwmc|hy ri|a |am
adwlrdwm lm~ikm dcl }{}dhhy uw`~ilm{ |am wmt}i{i|m ic|mww}u| adclhicbcmkm{{dwy n`w dcy |ifm&lmumclmc| adwlrdwm ic|mwndkicb cmml{#
\am omy lm{ibc b`dh `n lm~ikm lwi~mw{ i{ dg{|wdk|i`c# M~mwy
f`lmh `n adwlrdwm i{ linnmwmc|# Cmrmw f`lmh{ dh{` dwm wmhmd{ml gy
fdc}ndk|}wmw{ |ad| uw`~ilm f`wm wmhidghm `w gm||mw umwn`wfdckm dcl
|am{m cmrmw f`lmh{ dwm `n|mc k`c|w`hhml linnmwmc|hy#
K`fu}|mw{ dcl |amiw `umwd|icb {y{|mf{ kdcc`| gm mqumk|ml |`
oc`r a`r |` k`c|w`h m~mwy lm~ikm g`|a c`r dcl ic |am n}|}wm# \`
{`h~m |ai{ uw`ghmf( `umwd|icb {y{|mf{ m{{mc|idhhy lik|d|m a`r m~mwy
|yum `n lm~ikm {a`}hl gm k`c|w`hhml# \am n}ck|i`c n |am lm~ikm lwi~mw
;7
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 33/95
i{ |amc |` |wdc{hd|m |am{m @[ fdcld|ml n}ck|i`c kdhh{ ic|` lm~ikm
{umkinik kdhh{#
Ic |am`wy( d cmr lm~ikm raika i{ k`c|w`hhml ic d cmr fdccmw
{a`}hl n}ck|i`c k`wwmk|hy i{ d {}i|dghm lwi~mw i{ d~dihdghm# \ai{ cmr
lwi~mw rihh ic{}wm |ad| |am lm~ikm duumdw{ |` `umwd|m d{ }{}dh nw`f |am
`umwd|icb {y{|mf’{ u`ic| `n ~imr n`w dcy umw{`c#
[`fm `umwd|icb {y{|mf{ k`fm ri|a uwm&ic{|dhhml lwi~mw{ `w d
~dwim|y `n k`ff`c lwi~mw{ |` ka``{m nw`f# Ramc y`} g}y d cmr uimkm
`n adwlrdwm {}ka d{ d j`y {|iko( |amy rihh `n|mc k`fm ri|a d li{o |ad|
k`c|dic{ |am lm~ikm lwi~mw |ad| y`} kdc ic{|dhh# @|amw lwi~mw{ `w
}uld|ml lwi~mw{ dwm d~dihdghm `chicm d| |am fdc}ndk|}wmw’{ rmg{i|m#
Duuhikd|i`c Ic|mwndkm
J}{| d{ lwi~mw{ uw`~ilm d rdy n`w duuhikd|i`c{ |` fdom }{m `n
adwlrdwm {}g{y{|mf{ ri|a`}| ad~icb |` oc`r m~mwy lm|dih `n |am
adwlrdwm"{ `umwd|i`c( duuhikd|i`c uw`bwdf ic|mwndkm{ !DUI{) hm|
duuhikd|i`c uw`bwdffmw{ }{m n}ck|i`c{ `n |am k`fu}|mw dcl `umwd|icb
{y{|mf ri|a`}| ad~icb |` liwmk|hy ommu |wdko `n dhh |am lm|dih{ ic |am
KU]"{ `umwd|i`c# Hm|"{ h``o d| |am mqdfuhm `n kwmd|icb d adwl li{o nihm
n`w a`hlicb ld|d |` {mm ray |ai{ kdc gm ifu`w|dc|#
D uw`bwdffmw rwi|icb dc duuhikd|i`c |` wmk`wl ld|d nw`f d
{kimc|inik ic{|w}fmc| fiba| rdc| |` dhh`r |am {kimc|i{| |` {umkiny |am
cdfm `n |am nihm kwmd|ml# \am `umwd|icb {y{|mf fiba| uw`~ilm dc DUI
n}ck|i`c cdfml FdomNihm n`w kwmd|icb nihm{# Ramc rwi|icb |am uw`bwdf(
|am uw`bwdffmw r`}hl ic{mw| d hicm |ad| h``o{ hiom |ai{:
;;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 34/95
FdomNihm _4( -Cdfm( 7V
Ic |ai{ mqdfuhm( |am ic{|w}k|i`c |mhh{ |am `umwd|icb {y{|mf |`
kwmd|m d nihm |ad| rihh dhh`r wdcl`f dkkm{{ |` i|{ ld|d !{ibciniml gy |am
4 && |am `|amw `u|i`c fiba| gm 5 n`w d {mwidh nihm)( rihh ad~m d cdfm
|yuml ic gy |am }{mw !-Cdfm) dcl rihh gm d {izm |ad| ~dwim{ lmumclicb
`c a`r f}ka ld|d i{ {|`wml ic |am nihm !{ibciniml gy |am 7 && `|amw
`u|i`c{ fiba| gm zmw` n`w d niqml {izm( dcl 4 n`w d nihm |ad| bw`r{ d{
ld|d i{ dllml g}| l`m{ c`| {awico ramc ld|d i{ wmf`~ml)# C`r( hm|"{
h``o d| rad| |am `umwd|icb {y{|mf l`m{ |` |}wc |am ic{|w}k|i`c ic|`
dk|i`c#
\am `umwd|icb {y{|mf {mcl{ d t}mwy |` |am li{o lwi~m |` bm| |am
h`kd|i`c `n |am niw{| d~dihdghm nwmm {|`wdbm h`kd|i`c#
Ri|a |ad| icn`wfd|i`c( |am `umwd|icb {y{|mf kwmd|m{ dc mc|wy ic
|am nihm {y{|mf {a`ricb |am gmbiccicb dcl mclicb h`kd|i`c{ `n |am nihm(|am cdfm `n |am nihm( |am nihm |yum( ram|amw |am nihm ad{ gmmc dwkai~ml(
raika }{mw{ ad~m umwfi{{i`c |` h``o d| `w f`liny |am nihm( dcl |am ld|m
dcl |ifm `n |am nihm"{ kwmd|i`c#
\am `umwd|icb {y{|mf rwi|m{ icn`wfd|i`c d| |am gmbiccicb `n |am
nihm |ad| ilmc|inim{ |am nihm( {m|{ }u |am |yum `n dkkm{{ u`{{ighm dcl
ickh}lm{ `|amw icn`wfd|i`c |ad| |im{ |am nihm |` |am duuhikd|i`c# Ic dhh `n
|ai{ icn`wfd|i`c( |am t}mwim{ |` |am li{o lwi~m dcl dllwm{{m{ `n |am
gmbiccicb dcl mclicb u`ic| `n |am nihm dwm ic n`wfd|{ amd~ihy lmumclmc|
`c |am fdc}ndk|}wmw dcl f`lmh `n |am li{o lwi~m#
;<
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 35/95
Gmkd}{m |am uw`bwdffmw ad{ rwi||mc |am uw`bwdf |` }{m |am DUI
n`w li{o {|`wdbm( |am uw`bwdffmw l`m{c"| ad~m |` ommu }u ri|a |am
ic{|w}k|i`c k`lm{( ld|d |yum{ dcl wm{u`c{m k`lm{ n`w m~mwy u`{{ighm
adwl li{o dcl |dum lwi~m# \am `umwd|icb {y{|mf & k`ccmk|ml |` lwi~mw{
n`w |am ~dwi`}{ adwlrdwm {}g{y{|mf{ & lmdh{ ri|a |am kadcbicb lm|dih{
`n |am adwlrdwm && |am uw`bwdffmw f}{| {ifuhy rwi|m k`lm n`w |am DUI
dcl |w}{| |am `umwd|icb {y{|mf |` l` |am wm{|#
DUI{ ad~m gmk`fm `cm `n |am f`{| a`|hy k`c|m{|ml dwmd{ `n |am
k`fu}|mw icl}{|wy ic wmkmc| ymdw{# K`fudcim{ wmdhizm |ad|
uw`bwdffmw{ }{icb |amiw DUI rihh }h|ifd|mhy |wdc{hd|m |ai{ ic|` |am
dgihi|y |` k`c|w`h dcl uw`ni| nw`f d udw|ik}hdw udw| `n |am icl}{|wy# \ai{
i{ `cm `n |am wmd{`c{ |ad| {` fdcy k`fudcim{ ad~m gmmc rihhicb |`
uw`~ilm duuhikd|i`c{ hiom wmdlmw{ `w ~imrmw{ |` |am u}ghik d| c` kadwbm#
\amy oc`r k`c{}fmw{ rihh wmt}m{| |ad| uw`bwdf{ |dom
dl~dc|dbm `n |am nwmm wmdlmw{( dcl duuhikd|i`c k`fudcim{ rihh gm wmdly
|` udy w`ydh|im{ |` dhh`r |amiw {`n|rdwm |` uw`~ilm |am n}ck|i`c{
wmt}m{|ml gy |am k`c{}fmw{#
D{ rm’~m {|d|ml gmn`wm( |amwm dwm `umwd|icb {y{|mf{ ic dhh {`w|{
`n uw`l}k|{ ‛ c`| j}{| k`fu}|mw{# Kmhh ua`cm{( L^L wmk`wlmw{( dcl
\i^` uhdymw{ dh{` ad~m `umwd|icb {y{|mf{( a`rm~mw( |a`{m @[{ dwm c`|
wmdlihy c`|ikmdghm |` |am k`c{}fmw dcl |amy l` c`| ad~m dcy k`c|w`h`~mw |amf#
\ai{ fiba| gm d b``l |ifm |` wm~imr {`fm `n |am k`fu}|mw
`umwd|icb {y{|mf{ |ad| dwm `c |am fdwom| |`ldy#
;=
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 36/95
FIKW@[@N\ RICL@R[
Gdko ic |am hd|m 4925’{( |r` mc|mwuwi{icb y`}cb k`fu}|mw
uw`bwdffmw{ cdfml Ud}h Dhhmc dcl Gihh Bd|m{ lm~mh`uml dc dldu|d|i`c
n`w |am GD[IK k`fu}|mw hdcb}dbm |ad| r`}hl amhu w}c cmrhy kwmd|ml
umw{`cdh k`fu}|mw j}{| k`ficb `c |am |mkac`h`by fdwom|# D{ ri|a dcy
|mkac`h`by( |amiw `wibicdh kwmd|i`c kadcbml dcl bwmr#
\am |r` nwimcl{ lmkilml |amy adl |am uw`l}k| dcl |am kdudgihi|y
|` gmk`fm {}kkm{{n}h( {` |amy n`wfml d k`fudcy c`r oc`rc d{
Fikw`{`n|# @~mw |am ymdw{( Fikw`{`n| ad{ bw`rc |` d bidc| ic |am
k`fu}|mw icl}{|wy ri|a {}kkm{{m{ cm~mw gmn`wm {mmc gy d ‘nw`f
{kwd|ka‖ mclmd~`w#
Fikw`{`n| rd{ wm{u`c{ighm n`w |am lm~mh`ufmc| `n c`| `chy
{m~mwdh k`fu}|mw hdcb}dbm{ hiom K@G@H dcl UD[KDH( g}| dh{` n`w |am
lm~mh`ufmc| `n |am mdwhim{| `umwd|icb {y{|mf F[&L@[# Ic udw|cmw{aiu
ri|a IGF( ra` rd{ j}{| ic|w`l}kicb |am umw{`cdh k`fu}|mw |` |am
icli~il}dh k`c{}fmw( dhh `n |am IGF k`fu}|mw{ }{ml F[&L@[ `c |amiw
{y{|mf{# \am ymdw rd{ 4914#
M~mc |a`}ba `wibicdhhy( |am Duuhm K`wu`wd|i`c rd{ ic k`fum|i|i`c
ri|a Fikw`{`n| dcl IGF( |am k`fudcy m~mc|}dhhy gmbdc r`woicb `c
lm~mh`uicb dc `umwd|icb {y{|mf n`w |am k`fudcy’{ Fdkic|`{a umw{`cdh
k`fu}|mw{#
;>
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 37/95
\amc( ic 491=( dc icl}{|wy kadcbicb uw`l}k| rd{ {|dw|icb |`
m~`h~m# \ai{ cmr `umwd|icb {y{|mf r`}hl umwn`wf fdcy n}ck|i`c{
dhwmdly ic F[&L@[( g}| |am linnmwmckm r`}hl gm |ad| |ai{ cmr uw`l}k|
r`}hl n`k}{ `c ‘b``my{‖ Bwduaikdh ]{mw Ic|mwndkm{#
\am lm~mh`ufmc| `n |am B]I r`}hl kadcbm |am r`whl `n
k`fu}|mw{ fdoicb i| md{imw n`w |am m~mwyldy k`c{}fmw |` cd~ibd|m
|amiw umw{`cdh k`fu}|mw# \am icl}{|wy rd{ kadcbicb ‛ dcl i| rd{
kadcbicb nd{|$
Ricl`r{ `umwd|icb {y{|mf fdlm |am r`whl `n umw{`cdh
k`fu}|icb dkkm{{ighm dcl md{y n`w |am m~mwyldy J`m# C`r( m~mc
{|}lmc|{ ic |am {ka``h{ rmwm dghm |` }{m umw{`cdh k`fu}|mw{ n`w |amiw
{ka``h r`wo dcl ic khd{{# C` `cm ocmr j}{| a`r ndw |ai{ cmr @[ r`}hl
|dom |am r`whl `n k`fu}|icb |mkac`h`by#
J}{| hiom ri|a dcy k`fu}|mw |mkac`h`by( kadcbm{ dwm k`c{|dc|hy
gmicb fdlm |` ifuw`~m `c |am uw`l}k|# Dn|mw |am ici|idh hd}cka `n Ricl`r{( {m~mwdh `|amw ~mw{i`c{ m~`h~ml mdka `cm `nnmwicb cmr
`u|i`c{ dcl cmr nmd|}wm{ dcl mdka ri|a |amiw `rc g}b{ dcl uw`ghmf{#
[`fm um`uhm rmwmc’| gib ndc{ `n Ricl`r{ gmkd}{m d| |ifm{ i|
{mmfml d{ in Fikw`{`n| r`}hl wmhmd{m |am uw`l}k| uwi`w |` n}hhy |m{|icb
i|# I| gmkdfm ndfml n`w kwd{am{ dcl g}b{ |ad| r`}hl kd}{m |am {y{|mf
|` gmad~m mwwd|ikdhhy( g}| Fikw`{`n| dllwm{{ml mdka uw`ghmf uw`fu|hydcl Ricl`r{ k`c|ic}ml |` gm \AM `umwd|icb {y{|mf `c |am fdwom|#
\am wmhmd{m `n Ricl`r{ ;#4 `umwd|icb {y{|mf rd{ wm~`h}|i`cdwy
ic |ad| i| `nnmwml }{mw{ f`wm `u|i`c{ |ad| k`}hlc’| gm n`}cl ri|a i|{
;2
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 38/95
uwmlmkm{{`w F[&L@[# @cm `n |am f`{| amhun}h icc`~d|i`c{ rd{ dllicb
|am }{m `n d f`}{m |` cd~ibd|m dcl fdciu}hd|m ld|d ri|a `cm adcl
{ifuhy dcl md{ihy# ;#4 dh{` bd~m }{mw{ |am k`c~mcimckm `n c`| ad~icb
|` fmf`wizm F[&L@[ k`ffdcl{#
Ricl`r{ ;#4 rd{ |am niw{| uw`l}k| |` n}hhy }|ihizm bwduaikdh }{mw
ic|mwndkm n`w md{m `n k`c|w`hhicb rad| |am k`fu}|mw r`}hl l`#
Ricl`r{ dh{` c`r dhh`rml |am }{mw |` f}h|i|d{o( fmdcicb |am }{mw
k`}hl c`r w}c f}h|iuhm duuhikd|i`c{ d| `ckm ri|a`}| ad~icb |` kh`{m `}|
`n mdka uw`bwdf gmn`wm w}ccicb dc`|amw#
\am cmq| fdj`w Ricl`r{ uw`l}k| |` ai| |am fdwom| rd{ Ricl`r{
9= wmhmd{ml ic 499= amckm |am cdfm$ Cmr nmd|}wm{ ickh}lml |am
n`hh`ricb:
‧ Uh}b dcl Uhdy & Dhh`r{ adwlrdwm lm~ikm{ |` gm d}|`fd|ikdhhy
ic{|dhhml ic|` |am k`fu}|mw ri|a |am uw`umw {`n|rdwm# L`m{ c`|
wmt}iwm j}fumw{ |` gm uhdyml ri|a
‧ ;7 Gi| & ;7&Gi| `umwd|icb {y{|mf dhh`ricb |am k`fu}|mw |` w}c
nd{|mw dcl f`wm mnnikimc|hy
‧ Wmbi{|wy & K`fgicm{ |am u`rmw `n f}h|iuhm k`cnib}wd|i`c nihm{
ic|` |r` nihm{( dhh`ricb |am {y{|mf k`cnib}wd|i`c{ |` gm h`kd|ml
md{imw
‧ Fmf`wy & Ricl`r{ 9= adl dc ifuw`~ml fmf`wy adclhicb
uw`km{{m{ k`fudwml |` Ricl`r{ ;#44
;1
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 39/95
‧ Wiba| f`}{m khiko & Dhh`r{ y`} cmr dkkm{{ dcl |mq|
fdciu}hd|i`c gy }|ihizicb g`|a g}||`c{ ic{|mdl `n `cm
‧ KL&Uhdymw & Mcadckml KL&Uhdymw ri|a ifuw`~ml }{dgihi|y dcl
D}|`Uhdy nmd|}wm#
Ricl`r{ 9= dh{` adl {`fm mq|wd {`n|rdwm ickh}lml Ricl`r{
Mquh`wmw( Udic|( [kdc Li{o( dcl [`}cl Wmk`wlmw# Bdfm{ rmwm dllml
d{ rmwm {y{|mf |``h{ |ad| r`}hl lm&nwdbfmc| |am adwl lwi~m dcl dhh`r
y`} |` gdko }u nihm{ n`w }{m hd|mw#
Ricl`r{ 9= rd{ {}kkmmlml gy Ricl`r{ 91 wmhmd{ml ic ‛ y`}
b}m{{ml i| ‛ 4991$ Raihm |am wmhmd{m `n |ai{ @[ rd{c’| d{ gib d{ 9=(
|am 91 ~mw{i`c {|ihh k`c|dicml {`fm {ibcinikdc| }uld|m{( niqm{( dcl
{}uu`w| n`w cmr umwiuamwdh{#
‧
Uw`|mk|i`c & Ricl`r{ 91 ickh}lml dlli|i`cdh uw`|mk|i`c n`wifu`w|dc| nihm{ `c y`}w k`fu}|mw {}ka d{ gdkoicb }u y`}w
wmbi{|wy d}|`fd|ikdhhy#
‧ Ifuw`~ml {}uu`w| & Ifuw`~ml {}uu`w| n`w cmr lm~ikm{ {}ka d{
DBU( Liwmk|Q( L^L( ][G( FFQ( m|k#
‧
ND\;7 & Ricl`r{ 91 adl |am kdudgihi|y `n k`c~mw|icb y`}w lwi~m|` ND\;7 ri|a`}| h`{icb dcy icn`wfd|i`c#
‧ Ic|mwndkm & ]{mw{ `n Ricl`r{ 9= dcl C\ r`}hl mcj`y |am {dfm
md{y ic|mwndkm#
;9
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 40/95
‧ UcU & Ifuw`~ml UcU {}uu`w|( |` lm|mk| lm~ikm{ m~mc gm||mw |adc
Ricl`r{ 9=#
‧ Ic|mwcm| Mquh`wmw <#5 & Ickh}lml Ic|mwcm| Mquh`wmw <#5
‧ K}{|`fizdghm \d{ogdw & Ricl`r{ dllml fdcy cikm cmr
nmd|}wm{ |` |am |d{ogdw raika 9= dcl C\ lil c`| ad~m#
‧ Uh}{$ & Ickh}lml nmd|}wm{ `chy n`}cl ic Fikw`{`n| Uh}{$ nwmm#
‧ Dk|i~m Lm{o|`u & Ickh}lml Dk|i~m Lm{o|`u raika dhh`rml n`w
}{mw{ |` k}{|`fizm |amiw lm{o|`u ri|a |am h``o `n |am Ic|mwcm|#
Ricl`r{ 91 dh{` }ubwdlml {`fm `n i|{ {mk}wi|y nmd|}wm{ dcl
dllml Lw# Rd|{`c raika i{ d lidbc`{|ik |``h |ad| rihh h``o n`w uw`ghmf{
`c y`}w k`fu}|mw dcl |amc `nnmw }u d wm{`h}|i`c d}|`fd|ikdhhy# \amy
dh{` dllml d fdic|mcdckm rizdwl |ad| dhh`r{ y`} {kaml}hm kmw|dic
fdic|mcdckm |d{o{ {}ka d{ [kdc Li{o |` gm w}c `ckm d rmmo#
Ic ommuicb ri|a |am |amfm `n cdficb ~mw{i`c{ `n Ricl`r{ dn|mw
|am ymdw i| rd{ wmhmd{ml( |am cmq| ~mw{i`c rd{ Ricl`r{ 7555#
Ricl`r{ 7555 rd{ oc`rc d{ |am uw`nm{{i`cdh ~mw{i`c dcl rd{ bmdwml
|`rdwl g}{icm{{ }{m# [`( i| rd{ `n|mc wmnmwwml |` d{ Ricl`r{
Uw`nm{{i`cdh#
<5
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 41/95
Nmd|}wm{ `n |ai{ cmr `umwd|icb {y{|mf ickh}lml:
‧ [}uu`w| n`w ND\4>( ND\;7 dcl C\N[#
‧ Ickwmd{ml }u|ifm `n |am {y{|mf dcl {ibcinikdc|hy nmrmw @[
wmg``| {kmcdwi`{#
‧ Ricl`r{ Ic{|dhhmw |wdko{ duuhikd|i`c{ dcl wmk`bcizm{ dcl
wmuhdkm{ fi{{icb k`fu`cmc|{#
‧
Uw`|mk|{ fmf`wy `n icli~il}dh duu{ dcl uw`km{{m{ |` d~`il d{icbhm duu gwicbicb |am {y{|mf l`rc
‧ Mckwyu|ml Nihm [y{|mf{ uw`|mk|{ {mc{i|i~m ld|d#
‧ [mk}wm ^iw|}dh Uwi~d|m Cm|r`woicb !^UC) {}uu`w|{ |}ccmhicb ic |`
uwi~d|m HDC `~mw u}ghik Ic|mwcm|#
‧ Umw{`cdhizml fmc}{ dldu| |` |am rdy y`} r`wo
‧ F}h|ihicb}dh ~mw{i`c dhh`r{ n`w ]{mw Ic|mwndkm dcl amhu |` {ri|ka(
gd{ml `c h`b`c#
‧ Ickh}lm{ gw`dlmw {}uu`w| n`w aiba&{umml cm|r`woicb lm~ikm{(
ickh}licb Cd|i~m D\F dcl kdghm f`lmf{#
‧ [}uu`w|{ ]ci~mw{dh [mwidh G}{ !][G) dcl IMMM 4;9< n`w bwmd|mw
gdclril|a lm~ikm{#
<4
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 42/95
Raihm |ad| fiba| c`| {`}cl {ibcinikdc| |` |am m~mwyldy k`fu}|mw
}{mw( |am{m cmr dl~dckmfmc|{ fdlm n`w d {f``|amw w}ccicb {y{|mf
ri|a f`wm kdudgihi|im{ |adc `|amw Ricl`r{ ~mw{i`c{#
\am ymdw 7555 dh{` {dr |am wmhmd{m `n Ricl`r{ FM `w Ricl`r{
Fihhmcci}f# \ai{ ~mw{i`c rd{ fmdc| d{ dc }ubwdlm n`w Ricl`r{ 9=
dcl 91 dcl rd{ lm{ibcml ri|a mcl }{mw{ ic ficl# @~mwdhh( Ricl`r{
FM ad{ |am h``o dcl nmmh `n Ricl`r{ 91 ri|a {`fm dlli|i`cdh niqm{ dcl
nmd|}wm{ c`| d~dihdghm ic uwm~i`}{ `umwd|icb {y{|mf{#
Raihm Ricl`r{ FM ickh}lm{ {`fm `n |am hd|m{| niqm{ dcl }uld|m{
dcl {`fm mc|ikicb cmr nmd|}wm{( |ai{ }uld|m rd{ wmk`ffmclml `chy
n`w }{mw{ |ad| fdy nicl `w rdc| {`fm `n |am cmr nmd|}wm{ `w n`w }{mw{
ra` dwm u}wkad{icb d cmr k`fu}|mw ri|a |ai{ `umwd|icb {y{|mf
ickh}lml#
Omy }uld|ml nmd|}wm{ ickh}lm:
‧ Wm~mw| gdko |` gdko}u `n k`fu}|mw & Ricl`r{ FM dhh`rml
|am }{mw |` d}|`fd|ikdhhy wm{|`wm dc `hl gdko}u ic kd{m nihm{ dwm
k`ww}u|ml `w lmhm|ml#
‧ Uw`|mk| ifu`w|dc| {y{|mf nihm{ & Ricl`r{ Fm dhh`rml |am
}{mw |` uw`|mk| ifu`w|dc| {y{|mf nihm{ dcl r`}hl c`| dhh`r |am{mnihm{ |` gm f`liniml gy dcy |yum `n `|amw {`n|rdwm#
<7
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 43/95
‧ F`~im mli|`w & Dhh`rml }{mw{ |` mli| dcl `w k`fgicm Fikw`{`n|
f`~im nihm{# Ifu`w|icb f`~im{ wmt}iwml dlli|i`cdh adwlrdwm#
‧ Ricl`r{ Fmlid Uhdymw & Ickh}lml Fmlid Uhdymw 2( raika
mcdghml }{mw{ d f`wm dl~dckml rdy `n hi{|mcicb dcl `wbdcizicb
|amiw fmlid nihm{#
Dcl |am cmq| ymdw ‛ 7554 ‛ {dr |am wmhmd{m `n Ricl`r{ QU
raika i{ |am ~mw{i`c f`{| }{mw{ ad~m |` ld|m# \am QU {|dcl{ n`w
mqumwimckml dcl k`fgicml |am |r` fdj`w Ricl`r{ `umwd|icb {y{|mf{
ic|` `cm# I| i{ d~dihdghm ic g`|a d a`fm d{ rmhh d{ d uw`nm{{i`cdh
mli|i`c#
Ricl`r{ QU i{ lm{ibcml f`wm n`w }{mw{ ra` fdy c`| gm ndfihidw
ri|a dhh `n Ricl`r{ nmd|}wm{ dcl ad{ {m~mwdh cmr dgihi|im{ |` fdom |am
Ricl`r{ mqumwimckm md{imw n`w |a`{m }{mw{#
Ricl`r{ QU ickh}lm{ ~dwi`}{ cmr nmd|}wm{ c`| n`}cl ic uwm~i`}{
~mw{i`c{ `n Fikw`{`n| Ricl`r{# Gmh`r i{ d hi{|icb `n {`fm `n |am{m cmr
nmd|}wm{#
‧ Cmr ic|mwndkm & d k`fuhm|mhy cmr h``o dcl dgihi|y |` kadcbm
|am h``o#
‧ ]uld|m{ & cmr nmd|}wm |ad| d}|`fd|ikdhhy `g|dic{ }uld|m{ nw`f
|am Ic|mwcm|#
<;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 44/95
‧ Ic|mwcm| Mquh`wmw > & Ickh}lm{ ic|mwcm| mquh`wmw > dcl cmr IF#
‧ F}h|ihicb}dh {}uu`w| & dllml {}uu`w| n`w linnmwmc| hdcb}dbm{#
Ic dlli|i`c |` |am dg`~m nmd|}wm{( Ricl`r{ QU l`m{ ickwmd{m
wmhidgihi|y ramc k`fudwml |` uwm~i`}{ ~mw{i`c{ `n Fikw`{`n| Ricl`r{#
Nicdhhy( |am f`{| wmkmc| }ubwdlm `n Ricl`r{ rd{ j}{| wmhmd{ml ic
7552# Kdhhml Ricl`r{ ^i{|d( |ai{ cmr ~mw{i`c i{ ic|mclml d{ dc
}ubwdlm |` QU dcl 7555 }{mw{# Raihm i| l`m{ ad~m fdcy cmr nmd|}wm{(
|ai{ ~mw{i`c i{ ic|mclml |` bi~m k`fu}|mw }{mw{ dc `~mwdhh gm||mw
mqumwimckm ri|a d lwdfd|ik cmr h``o#
Dllml nmd|}wm{ `~mw uwm~i`}{ Ricl`r{ ~mw{i`c{ ickh}lm:
‧ Ricl`r{ Dmw`( d k`fuhm|mhy cmr B]I dcl }chiom dcy uwm~i`}{
~mw{i`c `n Ricl`r{#
‧ Gd{ik nihm gdko}u dcl wm{|`wm#
‧ Ifuw`~ml L^L {}uu`w| ri|a |am dgihi|y |` md{ihy kwmd|m k}{|`f
L^L f`~im{#
‧ Md{y |wdc{nmw( d nmd|}wm |ad| dhh`r{ y`} |` md{ihy |wdc{nmw nihm{
nw`f dc `hlmw k`fu}|mw |` |am cmr k`fu}|mw#
‧ Nihm mckwyu|i`c#
<<
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 45/95
‧ Ic{|dc| {mdwka d~dihdghm |aw`}ba dhh Mquh`wmw ricl`r{#
‧ [}uu`w| n`w Liwmk|Q 45#
‧ [mhn&amdhicb( |am dgihi|y |` d}|`fd|ikdhhy lm|mk| dcl k`wwmk|
uw`ghmf{ |ad| fdy gm mck`}c|mwml `c |am k`fu}|mw#
‧ [adl`r k`uy( d nmd|}wm |ad| dhh`r{ y`} |` wmk`~mw lmhm|ml nihm{#
‧ Ifuw`~ml ua`|` bdhhmwy dcl k`c|w`h `n ua`|`bwdua{#
‧ Ricl`r{ [ilmgdw dcl bdlbm|{ |ad| dhh`r{ y`} |` dll dc dhf`{|
mclhm{{ hi{| `n linnmwmc| bdlbm|{#
‧ F`wm udwmc|dh k`c|w`h#
‧ Ifuw`~ml Ricl`r{ Kdhmcldw( ri|a |am dgihi|y |` {m| |d{o{ dcl
duu`ic|fmc|{#
‧ Dcl f}ka f`wm#
[`fm um`uhm ra` dwm Ricl`r{ mc|a}{id{|{ adih |ai{ cmr uw`l}k|
d{ d {|mu ic|` d cmr |mkac`h`bikdh mwd# Ricl`r{ ^i{|d i{ nhd{ay( uwm||y(
dcl ifuwm{{i~m( g}| i| k`fm{ ri|a i|{ `rc }cit}m nd}h|{ d{ rmhh#
Wm~imrmw{ wmu`w| |ad| |amwm dwm fdcy lm~ikm lwi~mw{ hdkoicb ic |am
{`n|rdwm dcl |ad| i|{ {izm wmt}iwm{ d hdwbm df`}c| `n fmf`wy raika
kdc kd}{m y`}w k`fu}|mw |` w}c {h`rmw dcl hm{{ mnnikimc|hy#
<=
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 46/95
Dhh ~mw{i`c{ `n Ricl`r{ l` k`fm ri|a |am `wibicdh F[&L@[
`umwd|icb {y{|mf ickh}lml ic |am gdkobw`}cl n`w |a`{m ‘`hl&{ka``hmw{‖
ra` rihh rdc| |` mc|mw |amiw `rc k`fu}|mw k`ffdcl{# Dhh ~mw{i`c{
dh{` k`fm ri|a d gd{ik r`wl uw`km{{icb uw`bwdf dcl Ic|mwcm| Mquh`wmw
n`w {}wnicb |am cm|# Y`} rihh nicl {|dcldwl bdfm{ {}ka d{ {`hi|diwm ic
Ricl`r{ d{ rmhh#
F`{| k`fu}|mw{ |`ldy dwm `}|ni||ml ri|a Ricl`r{ QU d{ |amiw
`umwd|icb {y{|mf( g}| ri|a |am wmhmd{m `n ^i{|d( |ad| rihh uw`gdghy
kadcbm ic |am cmdw n}|}wm# \am Fikw`{`n| Ricl`r{ `umwd|icb {y{|mf i{
|am f`{| u`u}hdw ka`ikm df`cb k`fu}|mw }{mw{ |`ldy( g}| |amwm dwm
`|amw `umwd|icb {y{|mf{#
Hm|’{ |dom d h``o d| |am f`{| u`u}hdw `umwd|icb {y{|mf n`w Duuhm
Fdkic|`{a k`fu}|mw{#
<>
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 47/95
FDK @[
Ic 491<( Duuhm K`fu}|mw ic|w`l}kml |am Duuhm Fdkic|`{a
umw{`cdh k`fu}|mw# \am niw{| ~mw{i`c rd{ |am Fdkic|`{a 471O f`lmh
raika kdfm g}clhml ri|a |am Fdk @[ `umwd|icb {y{|mf |amc oc`rc d{
|am ‘[y{|mf [`n|rdwm‖# \am Fdk i{ `n|mc kwmli|ml ri|a u`u}hdwizicb
|am bwduaikdh }{mw ic|mwndkm !B]I)#
\am Fdk @[ ad{ gmmc uwm&ic{|dhhml `c dhf`{| m~mwy Fdkic|`{a
k`fu}|mw m~mw { hl# \am `umwd|icb {y{|mf i{ dh{` {`hl {mudwd|mhy nw`f
|am k`fu}|mw j}{| d{ ri|a Fikw`{`n| Ricl`r{# \am `wibicdh Fdk @[
rd{ amd~ihy gd{ml `c |am Hi{d @[ uwm~i`}{hy wmhmd{ml gy Duuhm n`w |amHi{d k`fu}|mw ic 491;# I| dh{` }{ml k`ckmu|{ nw`f |amw `umwd|icb
{y{|mf{ uwm~imrml gy Duuhm mqmk}|i~m{#
Ic 491<( Duuhm udw|cmwml ri|a Fikw`{`n| ic dc dbwmmfmc| |ad|
r`}hl ad~m Fikw`{`n| kwmd|icb ~mw{i`c{ `n R`wl dcl Mqkmh n`w |am Fdk
@[# N`w |am fdj`wi|y `n |am 4915’{( |am Fdk @[ hdkoml d hdwbm df`}c|
`n k`fud|ighm {`n|rdwm( a`rm~mw( |am ic|w`l}k|i`c `n [y{|mf 2 {dr
f`wm {`n|rdwm gmk`ficb d~dihdghm n`w |am uhd|n`wf#
[y{|mf > rd{ |am niw{| fdj`w wm~i{i`c `n |am `umwd|icb {y{|mf(
dh|a`}ba |am Fdk @[ omwcmh rd{ omu| |am {dfm nw`f |am [y{|mf 2
wm~i{i`c }c|ih Fdk @[ 9#
\am Fdkic|`{a uw`jmk| {|dw|ml ic mdwhy 4929 ri|a Jmnn Wd{oic ra`
mc~i{i`cml dc md{y&|`&}{m h`r&k`{| k`fu}|mw n`w |am d~mwdbmk`c{}fmw# Ic [mu|mfgmw `n ’29( Wd{oic rd{ bi~mc umwfi{{i`c |` {|dw|
aiwicb n`w |am uw`jmk|#
Ic Jdc}dwy `n 4914( [|m~m J`g{ k`fuhm|mhy |``o `~mw |am
Fdkic|`{a uw`jmk|# J`g{ dcl d c}fgmw `n Duuhm mcbicmmw{ ~i{i|ml
<2
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 48/95
Qmw`q UDWK ic Lmkmfgmw `n 4929 raika rd{ |awmm f`c|a{ dn|mw |am
Hi{d dcl Fdkic|`{a uw`jmk| adl gmb}c#
Dn|mw amdwicb dg`}| |am ui`cmmwicb B]I |mkac`h`by gmicb
lm~mh`uml d| Qmw`q UDWK nw`f n`wfmw mfuh`ymm{ hiom Wd{oic( J`g{
cmb`|id|ml d ~i{i| |` {mm |am Qmw`q Dh|` k`fu}|mw dcl [fdhh|dho
lm~mh`ufmc| |``h{ ic mqkadcbm n`w {|`ko `u|i`c{# \ai{ rd{ uw`gdghy
`cm `n |am gm{| g}{icm{{ f`~m{ J`g{ adl m~mw fdlm#
\am nicdh Hi{d dcl Fdkic|`{a `umwd|icb {y{|mf{ }{ml k`ckmu|{
nw`f |am Qmw`q Dh|`( g}| fdcy mhmfmc|{ `n |am B]I rmwm kwmd|icb gy
Duuhm ickh}licb d fmc} gdw dcl u`u&}u fmc}{# [umkinikdhhy( |am khiko
dcl lwdb k`ckmu| rd{ lm~mh`uml gy Jmnn Wd{oic#
]chiom |am IGF UK raika }{ml 1 OG `n {y{|mf W@F n`w u`rmw&`c
{mhn |m{| dcl gd{ik icu}|/`}|u}| ka`wm{( |am Fdk W@F rd{ {ibcinikdc|hy
hdwbmw d| >< OG dcl amhl omy @[ k`lm# Dcly Amw|znmhl rd{ wm{u`c{ighm
n`w f`{| `n |am `wibicdh k`licb# Am rd{ dghm |` k`c{mw~m {`fm `n |am
W@F {udkm gy ic|mwrmd~icb {`fm `n |am d{{mfghy hdcb}dbm k`lm#
Ic dlli|i`c |` k`licb |am W@F( am dh{` k`lml |am omwcmh( |am
Fdkic|`{a \``hg`q( dcl {`fm `n |am lm{o|`u dkkm{{`wim{ d{ rmhh# \am
ik`c{ `n |am `umwd|icb {y{|mf raika wmuwm{mc|ml n`hlmw{ dcl
duuhikd|i`c {`n|rdwm rmwm lm{ibcml gy [}{dc Odwm ra` hd|mw lm{ibcml
|am ik`c{ n`w Fikw`{`n| Ricl`r{ ;#5#
Duuhm rd{ ~mwy {|w`cb ic dl~mw|i{icb |ai{ cmr fdkaicm# Dn|mw i|
rd{ kwmd|ml( |amy dk|}dhhy g`}ba| `}| dhh |aiw|y&cicm udbm{ `n
dl~mw|i{mfmc| {udkm ic Cmr{rmmo Fdbdzicm’{ C`~mfgmw/Lmkmfgmw(
491< mli|i`c# I| r`woml ickwmlighy rmhh dcl |am ic~m{|fmc| udil `nn d{
Fdk{ gmbdc nhyicb `nn |am {amh~m{#
<1
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 49/95
\am niw{| ~mw{i`c `n Fdk @[ dh`cb ri|a {}g{mt}mc| }uld|m{ rmwm
linnmwmc| nw`f `|amw `umwd|icb {y{|mf{ ic |ad| |ai{ @[ lilc’| }{m
k`ffdcl hicm ic|mwndkm g}| wd|amw }{mw nwimclhy ic|mwndkm# Fdcy um`uhm
|aico |ad| Ricl`r{ rd{ |am niw{| |` mfuh`y B]I( g}| Fdk adl |amf
gmd|#
]uld|m{ |` |am @[ f`{|hy n`k}{ml `c kadcbm{ |` |am ‘niclmw‖
raika i{ dc duuhikd|i`c n`w nihm fdcdbmfmc| raika dh{` li{uhdy{ |am
lm{o|`u# Uwi`w |` ~mw{i`c =( |am niclmw k`}hl `chy w}c cm duuhikd|i`c
d| d |ifm# Ramc ~mw{i`c = rd{ wmhmd{ml( i| k`c|dicml f}h|i&niclmw
raika k`}hl w}c {m~mwdh duuhikd|i`c{ d| `ckm#
\ifm rd{ bi~mc |` gdkobw`}cl duuhikd|i`c{ `chy ramc |am
n`wmbw`}cl w}ccicb duuhikd|i`c{ bd~m i| }u ic k`&`umwd|i~m
f}h|i|d{oicb( g}| ic ndk| f`{| `n |amf lil ~id d khm~mw kadcbm ic |am
`umwd|icb {y{|mf’{ m~mc| adclhicb#
[y{|mf = dh{` gw`}ba| K`h`w T}iko Lwdr |` |am Fdk II# \ai{
{ibcinikdc|hy dh|mwml |am mq|mc| dcl lm{ibc `n |am }clmwhyicb bwduaik{
dwkai|mk|}wm g}| i| i{ d kwmli| |` Duuhm |ad| f`{| }{mw{( dcl umwadu{
f`wm ifu`w|dc|hy mqi{|icb k`lm( rmwm hdwbmhy }cdrdwm `n |ai{#
[y{|mf [`n|rdwm = rd{ dh{` |am niw{| FDK `umwd|icb {y{|mf |`
gm bi~mc d }ciniml {y{|mf {`n|rdwm ~mw{i`c c}fgmw d{ `uu`{ml |` |am
c}fgmw{ }{ml n`w |am {y{|mf dcl niclmw nihm{#
Ic 4994( [y{|mf 2 rd{ wmhmd{ml# I| rd{ |am {mk`cl fdj`w
}ubwdlm |` |am Fdk @[ dllicb d {ibcinikdc| }{mw ic|mwndkm `~mwad}h(
cmr duuhikd|i`c{( {|dgihi|y ifuw`~mfmc|( dcl fdcy cmr nmd|}wm{#
\am f`{| ~i{ighm kadcbm rd{ d cmr n}hh&k`h`w }{mw ic|mwndkm#
Dh|a`}ba |ai{ nmd|}wm fdlm n`w d ~i{}dhhy duumdhicb ic|mwndkm( i| rd{
<9
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 50/95
`u|i`cdh# @c fdkaicm{ c`| kdudghm `n li{uhdyicb k`h`w `w |a`{m ri|a
|amiw li{uhdy uwmnmwmckm{ {m| |` f`c`kaw`fm( |am ic|mwndkm lmnd}h|ml
gdko |` |am ghdko dcl rai|m `n uwm~i`}{ ~mw{i`c{# @chy {`fm ic|mwndkm
mhmfmc|{ rmwm k`h`wizml: {kw`hhgdw{ adl d cmr h``o g}| u}{a g}||`c{
wmfdicml ic ghdko dcl rai|m#
\am gibbm{| nmd|}wm dllml ic {y{|mf 2 ickh}lml |am g}ih|&ic k`&
`umwd|i~m f}h|i|d{oicb# Ic {y{|mf >( |ai{ n}ck|i`c rd{ `u|i`cdh
|aw`}ba |am f}h|i niclmw# [y{|mf 2 dh{` ic|w`l}kml dhid{m{ raika dwm
{ifihdw |` {a`w|k}|{ |ad| rmwm ic|w`l}kml ic hd|mw ~mw{i`c{ `n Ricl`r{#
[y{|mf mq|mc{i`c{ rmwm mcadckml gy gmicb f`~ml |` |amiw `rc
{}gn`hlmw# D {}gn`hlmw ic |am {y{|mf n hlmw rd{ dh{` kwmd|ml n`w |am
k`c|w`h udcmh{# D {fdhhmw }uld|m ‛ l}ggml {y{|mf 2#= ‛ ickh}lml |am
mq|mc{i`c{ fdcdbmw( d uwm~i`}{hy |aiwl udw|y uw`bwdf raika {ifuhiniml
|am uw`km{{ `n mcdghicb dcl li{dghicb mq|mc{i`c{#
[y{|mf 2 f`~ml |am Fdk |` |w}m ;7&gi| fmf`wy dllwm{{icb
cmkm{{dwy n`w |am m~mwy&ickwmd{icb df`}c|{ `n WDF d~dihdghm# Mdwhimw
{y{|mf{ }{ml |am h`rmw 7< gi|{ n`w dllwm{{icb dcl |am }uumw 1 gi|{ n`w
nhdb{# \ai{ rd{ dc mnnmk|i~m {`h}|i`c n`w mdwhimw Fdk f`lmh{ ri|a ~mwy
hifi|ml df`}c|{ `n WDF( g}| i| gmkdfm d hidgihi|y hd|mw# ^iw|}dh
fmf`wy {}uu`w| rd{ dh{` dllml d{ d {mudwd|m( `u|i`cdh nmd|}wm#
\am Duuhm fmc}( a`fm `chy |` lm{o dkkm{{`wim{ ic {y{|mf > rd{
fdlm f`wm bmcmwdh u}wu`{m: |am }{mw k`}hl c`r fdom `n|mc&}{ml
n`hlmw{ dcl duuhikd|i`c{ ‛ `w dcy|aicb mh{m |amy lm{iwml ‛ duumdw ic |am
fmc} gy uhdkicb dhid{m{ |` |amf ic dc ‘Duuhm Fmc} I|mf{‖ {}gn`hlmw `n
|am {y{|mf n`hlmw#
=5
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 51/95
\am |wd{a n`hlmw( }clmw {y{|mf > dcl mdwhimw( r`}hl mfu|y i|{mhn
d}|`fd|ikdhhy ramc {a}||icb l`rc |am k`fu}|mw `w( in f}h|i&niclmw
rmwm c`| w}ccicb( ramc hd}ckaicb dc duuhikd|i`c# [y{|mf 2 wm&
ifuhmfmc|ml |am |wd{a d{ d {umkidh aillmc n`hlmw dhh`ricb nihm{ |`
wmfdic ic i| dkw`{{ wmg``|{ }c|ih |am }{mw lmhigmwd|mhy ka`{m |am ‘Mfu|y
\wd{a‖ k`ffdcl#
\amwm rmwm {`fm `|amw ‘aiba hm~mh‖ dlli|i`c{ ic {y{|mf 2# Fdcy
um`uhm nmh| |ad| Duuhm lw`uuml |am gdhh `c {`fm `n |am{m dlli|i`c{ dcl
dkk}{ml |am k`fudcy `n c`| n}hhy |aicoicb |aw`}ba |am{m }uld|m{#
Fikw`{`n| rd{ dkk}{ml `n |am {dfm |aicb ri|a mdwhimw ~mw{i`c{ `n
Ricl`r{ d{ rmhh#
@cm `n |am f`{| k`cn}{icb d{umk|{ `n |am Fdk @[ rd{ |am
wmhidckm `c k`}c|hm{{ [y{|mf Mcdghmw{ |` {}uu`w| cmr adwlrdwm raika
r`}hl uw`~m |` uhdb}m |am Fdk @[ dhh |am rdy |` ~mw{i`c 1 dn|mw raika
iFdk ic|w`l}kml i|{ ‘Cmr R`whl‖ dwkai|mk|}wm# Dh|a`}ba |am iFdk i|{mhn
wmt}iwm{ d {y{|mf mcdghmw ri|a @[ 1 d{ `|amw Fdk{ wmhmd{ml d| |ad|
|ifm( Fdk{ wmhmd{ml dn|mw |am iFdk l` c`| wmt}iwm d {y{|mf mcdghmw#
Dc`|amw uw`ghmf mck`}c|mwml rd{ |ad| ~dwi`}{ {y{|mf }uld|m
mq|mc{i`c{ ri|a ick`c{i{|mc| ~mw{i`c c}fgmwicb {kamfm{# @~mwdhh
{|dgihi|y dcl umwn`wfdckm `n |am Fdk @[ bwdl}dhhy r`w{mcml l}wicb
|ai{ |ifm raika ic|w`l}kml U`rmw UK {}uu`w| dcl >1O mf}hd|i`c#
Ramc ~mw{i`c @[ 2#> rd{ wmhmd{ml( |am {|dgihi|y `n |am `umwd|icb
{y{|mf rd{ f}ka gm||mw# Um`uhm gmbdc |` n}hhy mfgwdkm |am Fdk @[
dcl |amiw hmbi|ifdky wm|}wcml d{ d u`u}hdw `umwd|icb {y{|mf#
=4
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 52/95
[y{|mf 2 dh{` {dr |am ic|w`l}k|i`c `n dc ic|mwdk|i~m amhu
duuhikd|i`c( dcl |am dlli|i`c `n ‘[|ikoim{‖ raika rmwm gd{ikdhhy ~iw|}dh
U`{|&I| c`|m{# Fdcy Fdk }{mw{ {|ihh ad~m @[ 2 `c |amiw Duuhm{#
\r` `|amw ~mw{i`c{ r`}hl n`hh`r ic @[ 1 dcl @[ 9 mdka
ifuw`~icb `c |am uwm~i`}{ ~mw{i`c# Duuhm k`c|ic}ml |` lm~mh`u
}uld|m{ |` |amiw `umwd|icb {y{|mf fdoicb i| f`wm {|dghm dcl kdudghm
`n f`wm |d{o{ r`woicb mnnikimc|hy |` gwicb Fdk ic|` |am 74 {| kmc|}wy#
\am f`{| wmkmc| ~mw{i`c dcl `cm |ad| i{ }{ml `c cmr {y{|mf{
|`ldy i{ Fdk @[ Q# \ai{ ~mw{i`c uw`~ilm{ d {|dghm `umwd|icb
mc~iw`cfmc| n`w |am Fdk UK dcl `nnmw{ f`wm nhmqigihi|y |adc `|amw
{y{|mf{# \am bwduaik{ dwm }uld|ml ri|a h`|{ `n k`h`w dcl d nhd{aimw
h``o#
=7
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 53/95
]CIQ
\am ]CIQ `umwd|icb {y{|mf rd{ lm~mh`uml ic |am >5’{ dcl 25’{
gy d bw`}u `n D\ . \ mfuh`ymm{ d| Gmhh Hdg{# ]ciq i{ }{ml gy g`|a
{mw~mw{ dcl r`wo{|d|i`c{ dcl i{ |am gd{i{ n`w d rilm ~dwim|y `n `|amw
`umwd|icb {y{|mf{#
\am ]CIQ {y{|mf rd{ lm{ibcml |` gm u`w|dghm( f}h|i&|d{oicb dcl
f}h|i&}{mw ic d |ifm&{adwicb k`cnib}wd|i`c# \amwm dwm ~dwi`}{ k`ckmu|{
|ad| dwm }cit}m |` dhh ]CIQ {y{|mf{# \am{m k`ckmu|{ ickh}lm:
‧ \am }{m `n uhdic |mq| n`w {|`wicb ld|d
‧ D aimwdwkaikdh nihm {y{|mf
‧ \wmd|icb lm~ikm{ dcl kmw|dic |yum{ `n ic|mw&uw`km{{
k`ff}cikd|i`c d{ nihm{
‧ \am }{m `n d hdwbm c}fgmw `n {fdhh uw`bwdf{ |ad| kdc gm {|w}cb
|`bm|amw |aw`}ba d k`ffdcl hicm ic|mwuwm|mw }{icb ‘uium{‖ d{
`uu`{ml |` d {icbhm f`c`hi|aik uw`bwdf ri|a |am {dfm
n}ck|i`cdhi|y#
\am `umwd|icb {y{|mf }clmw ]CIQ k`c{i{|{ `n fdcy `n |am
}|ihi|im{ hi{|ml dg`~m dh`cb ri|a |am fd{|mw k`c|w`h uw`bwdf raika i{
kdhhml |am ‘omwcmh‖# \am omwcmh amhu{ {|dw| dcl {|`u uw`bwdf{( adclhm
|am nihm {y{|mf( |dom kdwm `n `|amw k`ff`c aiba hm~mh |d{o{ |ad| f`{|
uw`bwdf{ {adwm dcl {kaml}hm dkkm{{ |` adwlrdwm |` d~`il k`cnhik|{ in
=;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 54/95
|r` uw`bwdf{ |wy |` dkkm{{ |am {dfm wm{`}wkm `w lm~ikm
{if}h|dcm`}{hy#
Gm{ilm{ |am fdic omwcmh( ]CIQ {y{|mf{ dh{` adl fikw`&omwcmh{
raika |wiml |` wm~mw{m |am bw`ricb {izm `n omwcmh{ dcl wm|}wc |` d
{y{|mf ic raika f`{| |d{o{ rmwm k`fuhm|ml gy {fdhhmw }|ihi|im{#
Ic dc mwd ramwm d ‘c`wfdh‖ k`fu}|mw k`c{i{|ml `n d adwl li{o n`w
{|`wdbm dcl d ld|d |mwficdh n`w icu}| dcl `}|u}|( |am ]CIQ nihm f`lmh
r`woml t}i|m rmhh d{ f`{| icu}|/`}|u}| rd{ hicmdw# A`rm~mw( f`lmwc
{y{|mf{ ickh}lm cm|r`woicb dcl `|amw cmr lm~ikm{#
Lm{kwigicb d bwduaikdh }{mw ic|mwndkm lwi~mc gy f`}{m k`c|w`h ic
dc ‘m~mc| lwi~mc‖ nd{ai`c lilc’| r`wo rmhh }clmw |am hl f`lmh# R`wo
`c {y{|mf{ {}uu`w|icb |am{m cmr lm~ikm{ ic |am 4915’{ hml |` ndkihi|im{
n`w c`c&gh`koicb icu}|/`}|u}| n`wf{ `n ic|mw&uw`km{{ k`ff}cikd|i`c{
`|amw |adc j}{| uium{( d{ rmhh d{ f`~icb n}ck|i`cdhi|y {}ka d{ cm|r`wo
uw`|`k`h{ `}| `n |am omwcmh#
J}{| d{ ri|a `|amw `umwd|icb {y{|mf{( |am uw`bwdfficb rd{
}uld|ml umwi`likdhhy |` dll `|amw nmd|}wm{ dcl |` {|wmdfhicm uw`km{{m{
|ad| |am {y{|mf r`}hl w}c# Iw`cikdhhy( |am ifu`w|dckm n |am ]CIQ
{y{|mf i{ t}i|m ndw&wmdkaicb# Ic ndk|( {`fm mqumw|{ kdhh i| |am f`{|
ifu`w|dc| {y{|mf y`}’hh cm~mw }{m#
]CIQ i{ f`{|hy }{ml gy Ic|mwcm| {mw~mw{ dcl ld|dgd{m {mw~mw{#
I| i{ d ~mwy mnnikimc| f}h|i&}{mw( f}h|i&|d{oicb `umwd|icb {y{|mf
|wdli|i`cdhhy }{ml gy hdwbm k`fudcim{ dcl ml}kd|i`cdh ic{|i|}|i`c{#
I| i{ {kdhdghm nw`f d {fdhh {y{|mf wiba| }u |` d fdicnwdfm&khd{{
{y{|mf !dhh y`} cmml |` l` i{ dll mq|wd adwlrdwm)( raika fdom{ i|
{}i|dghm n`w dcy`cm h``oicb n`w d h`r k`{|( wmhidghm `umwd|icb {y{|mf#
=<
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 55/95
N`w uw`bwdffmw{ i| ad{ d r`clmwn}h {m| `n g}ih|&ic }|ihi|im{( d
uw`bwdffdghm {amhh !k`ffdcl/}{mw ic|mwndkm) dcl d {|wdiba| n`wrdwl
{|w}k|}wm |ad| fdom{ i| ~mwy md{y |` t}ikohy uw`l}km t}i|m k`fuhmq
uw`bwdf{# N`w mcl }{mw{( ]CIQ ad{ d nwimclhy bwduaikdh ic|mwndkm
!kdhhml Q Ricl`r{) dcl fdcy g}{icm{{ duuhikd|i`c{ dcl bdfm{#
D{ rm {dil( ]CIQ i{ }{ml d{ d gd{i{ n`w `|amw `umwd|icb {y{|mf{#
@cm `n |a`{m i{ Hic}q#
==
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 56/95
HIC]Q
\am niw{| Hic}q {y{|mf{ rmwm k`fuhm|ml ic 4997 gy k`fgicicb
{y{|mf }|ihi|im{ dcl higwdwim{ nw`f |am BC] uw`jmk| raika i{ dc`|amw
`umwd|icb {y{|mf rm’hh dllwm{{ cmq|#
Uwml`ficdc|hy oc`rc n`w i|{ }{m ic {mw~mw{( Hic}q i{ }{ml d{ dc
`umwd|icb {y{|mf n`w d rilmw ~dwim|y `n k`fu}|mw adwlrdwm |adc dcy
`|amw `umwd|icb {y{|mf ickh}licb lm{o|`u k`fu}|mw{( {}umw
k`fu}|mw{( fdicnwdfm{( dcl mfgmllml lm~ikm{ {}ka d{ kmhh ua`cm{#
Hic}q i{ udkodbml n`w linnmwmc| }{m{ ic Hic}q li{|wig}|i`c{ raika
k`c|dic |am omwcmh dh`cb ri|a d ~dwim|y `n `|amw {`n|rdwm udkodbml
|dih`wml |` i|{ ic|mclml }{m#
Hic}q dhhmbm{ |ad| um`uhm wmbdwl |am {y{|mf d{ {}i|dghm f`{|hy
n`w k`fu}|mw mqumw|{ gmkd}{m fdic{|wmdf k`fu}|mw fdbdzicm wmu`w|{
kdcc`| mquhdic rad| Hic}q i{ ic d fmdcicbn}h rdy d{ |amy hdko wmdh&hinm
mqumwimckm }{icb i|# N}w|amwf`wm( |am nwik|i`cdh k`{| `n {ri|kaicb
`umwd|icb {y{|mf{ dcl hdko `n {}uu`w| n`w kmw|dic adwlrdwm dcl
duuhikd|i`c uw`bwdf{ lm{ibcml n`w Fikw`{`n| Ricl`r{ ad~m gmmc |r`
ndk|`w{ |ad| ad~m icaigi|ml dl`u|i`c#
A`rm~mw( d{ `n mdwhy 7552( {ibcinikdc| uw`bwm{{ ic adwlrdwm
k`fud|igihi|y ad{ gmmc fdlm( dcl i| i{ gmk`ficb ickwmd{icbhy k`ff`c
n`w adwlrdwm |` r`wo ‘`}| `n |am g`q‖ ri|a fdcy Hic}q li{|wig}|i`c{#
Uw`u`cmc|{ dcl dcdhy{|{ d||wig}|m |am wmhd|i~m {}kkm{{ `n Hic}q |` i|{
{mk}wi|y( wmhidgihi|y( h`r k`{|( dcl nwmml`f nw`f ~mcl`w h`ko&ic#
\am uwifdwy linnmwmckm gm|rmmc Hic}q dcl `|amw k`c|mfu`wdwy
`umwd|icb {y{|mf{ i{ |ad| |am Hic}q omwcmh dcl `|amw k`fu`cmc|{ dwm
`umc {`}wkm {`n|rdwm# \ad| fmdc{ |ad| }{mw{ ad~m umwfi{{i`c |`
=>
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 57/95
{|}ly( kadcbm( dcl ifuw`~m |am {`n|rdwm# \amy kdc |amc wmli{|wig}|m
i| ic f`liniml `w }cf`liniml n`wf# \ai{ i{ }{}dhhy l`cm ic d u}ghik dcl
k`hhdg`wd|i~m fdccmw#
Hic}q i{ c`| |am `chy {}ka `umwd|icb {y{|mf( dh|a`}ba i| i{ |am
f`{| rmhh&oc`rc dcl rilmhy }{ml `cm# [`fm `umc {`}wkm hikmc{m{ dwm
gd{ml `c |am uwickiuhm `n ‘k`uy hmn|‖( d oicl `n wmkiuw`ki|y: dcy r`wo
lmwi~ml nw`f d k`uy hmn| uimkm `n {`n|rdwm f}{| dh{` gm k`uy hmn| i|{mhn#
@cm `n |am dl~dc|dbm{ `n `umc {`}wkm i{ |ad| i| dhh`r{ n`w wduil
{`n|rdwm g}b lm|mk|i`c dcl mhificd|i`c raika i{ ifu`w|dc| n`w
k`wwmk|icb {mk}wi|y mquh`i|{#
Dc`|amw dl~dc|dbm `n Hic}q d{ dc `umwd|icb {y{|mf i{ ic|mw&
`umwdgihi|y# \ad| fmdc{( i| kdc w}c {`n|rdwm nw`f `|amw k`fudcim{
{}ka d{ Fdk dcl Ricl`r{# \ai{ fdom{ i| a}bmhy dl~dc|dbm`}{ |` |am
`umc fdwom| d{ ic|mw&`umwdgihi|y ic dc `umwd|icb {y{|mf i{ wd|amw
}ck`ff`c d{ `n hd|m#
Um`uhm ad~m dk|}dhhy |domc `c |am uw`f`|i`c `n Hic}q ic rad|
fiba| gm k`c{ilmwml dhf`{| d k}h|&hiom n`hh`ricb# Ic fdcy ki|im{ dcl
wmbi`c{( h`kdh d{{`kid|i`c{ oc`rc d{ Hic}q ]{mw{ Bw`}u{# \amy {mmo |`
uw`f`|m Hic}q dcl( gy mq|mc{i`c( |am c`|i`c dcl wmdhi|y `n nwmm
{`n|rdwm# \amy dk|}dhhy a`hl fmm|icb{ dcl uw`~ilm nwmm
lmf`c{|wd|i`c{( |wdicicb( |mkacikdh {}uu`w|( dcl `umwd|icb {y{|mf
ic{|dhhd|i`c |` cmr }{mw{#
\amwm dwm dh{` fdcy Ic|mwcm| k`ff}ci|im{ |ad| {mmo |` uw`~ilm
{}uu`w| |` Hic}q }{mw{ dcl lm~mh`umw{# F`{| li{|wig}|i`c{ dcl `umc
{`}wkm uw`jmk|{ ad~m d kad| w``f c |am nwmmc`lm IWK cm|r`wo# \am{m
kad| w``f{ dwm umc |` dcy`cm ri|a dc IWK khimc|# @chicm n`w}f{ dwm
=2
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 58/95
dc`|amw fmdc{ n`w {}uu`w| ri|a c`|dghm mqdfuhm{ gmicb
rrr#hic}qt}m{|i`c{#`wb#
M~mwy m{|dghi{aml nwmm {`n|rdwm uw`jmk| dcl Hic}q li{|wig}|i`c
ad{ `cm `w f`wm fdihicb hi{|{# K`ff`chy |amwm rihh gm d {umkinik |`uik
{}ka d{ }{dbm `w lm~mh`ufmc| n`w d bi~mc hi{|#
Dh|a`}ba Hic}q i{ bmcmwdhhy d~dihdghm nwmm `n kadwbm( {m~mwdh hdwbm
k`wu`wd|i`c{ ad~m m{|dghi{aml g}{icm{{ f`lmh{ |ad| ic~`h~m {mhhicb(
{}uu`w|icb( dcl k`c|wig}|icb |` Hic}q dcl nwmm {`n|rdwm# \am nwmm
{`n|rdwm hikmc{m{ `c raika Hic}q i{ gd{ml mquhiki|hy dkk`ff`ld|m dcl
mck`}wdbm k`ffmwkidhizd|i`c#
D{ `n hd|m( hi~mhy li{k}{{i`c{ df`cb k`fu}|mw mc|a}{id{|{ ad~m
dwi{mc `~mw raika i{ |am gm{| umwd|icb {y{|mf |` }{m: Ricl`r{ `w
Hic}q0 Ic |am ud{|( nwmm {`n|rdwm uw`l}k|{ ad~m gmmc kwi|ikizml n`w c`|
b`icb ndw mc`}ba |` ic{}wm md{m `n }{m# A`rm~mw( {`fm mqumw|{ ad~m
lmkhdwml |ad| Hic}q i{ cmdwhy mt}dh |` Ricl`r{ n`w md{m `n }{m d{ rmhh
d{ k`fud|igihi|y ri|a `|amw uw`bwdf{#
Fdcy Ricl`r{ duuhikd|i`c{ kdc gm w}c `c |am Hic}q `umwd|icb
{y{|mf# Raihm |amwm dwm c`| fdcy bdfm{ `w duuhikd|i`c{ |ad| dwm
d~dihdghm ri|a Hic}q( |amwm dwm {|ihh `|amw{ |ad| kdc w}c md{ihy `c |am
{`n|rdwm#
=1
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 59/95
BC]
Hiom Hic}q( BC] !uw`c`}ckml b}a&c``) i{ dh{` d nwmm {`n|rdwm
`umwd|icb {y{|mf# I|{ cdfm i{ d wmk}w{i~m dkw`cyf n`w ‘BC]’{ c`|
]ciq‖ raika rd{ ka`{mc gmkd}{m raihm i| i{ ]ciq gd{ml( i| i{ nwmmrdwm
dcl k`c|dic{ c` ]ciq k`lm# D{ `n 7552( BC] i{ gmicb dk|i~mhy
lm~mh`uml dh|a`}ba d k`fuhm|m {y{|mf ad{ c`| ym| gmmc wmhmd{ml#
\am bmc|hmfdc wm{u`c{ighm n`w lm~mh`uicb BC] i{ Wikadwl
[|dhhfdc( d n`wfmw mfuh`ymm d| FI\# Am gmhim~ml k`fu}|mw }{mw{
{a`}hl gm nwmm( d{ f`{| rmwm ic |am 49>5{ dcl 4925{? nwmm |` {|}ly
|am {`}wkm k`lm `n |am {`n|rdwm |amy }{m( nwmm |` {adwm |am {`n|rdwm
ri|a `|amw um`uhm( nwmm |` f`liny |am gmad~i`w `n |am {`n|rdwm( dcl
nwmm |` u}ghi{a |amiw f`liniml ~mw{i`c{ `n |am {`n|rdwm# \ai{ uaih`{`uay
rd{ u}ghi{aml ic Fdwka 491= d{ |am BC] Fdcinm{|`#
F}ka `n |am cmmlml {`n|rdwm adl |` gm rwi||mc nw`f {kwd|ka( g}|
mqi{|icb k`fud|ighm nwmm {`n|rdwm k`fu`cmc|{ rmwm }{ml# F`{| `n
BC] ad{ gmmc rwi||mc gy ~`h}c|mmw{? {`fm ic |amiw {udwm |ifm( {`fm
udil gy k`fudcim{( ml}kd|i`cdh ic{|i|}|i`c{( dcl `|amw c`c&uw`ni|
`wbdcizd|i`c{#
Ic 4997( |am `umwd|icb {y{|mf rd{ f`wm `w hm{{ nici{aml mqkmu|
n`w |am omwcmh# \am BC] uw`jmk| adl d fikw`omwcmh( dcl |` dll |am
cmkm{{dwy ]ciq&omwcmh&hiom n}ck|i`cdhi|y |` |amiw fikw`omwcmh( |amy rmwm
lm~mh`uicb d uw`jmk| kdhhml ‘A}wl‖# A`rm~mw( ‘A}wl‖ rd{ {|ihh ~mwy
ick`fuhm|m#
\ad| ymdw( Hic}{ \`w~dhl{ wmhmd{ml ai{ ]ciq&hiom omwcmh Hic}q d{
nwmm {`n|rdwm# \am k`fgicd|i`c `n |am Hic}q omwcmh dcl |am BC]
{y{|mf fdlm n`w d ra`hm( ]ciq&hiom nwmm {`n|rdwm `umwd|icb {y{|mf#
=9
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 60/95
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 61/95
@\AMW @UMWD\ICB [Y[\MF[
Raihm rm ad~m k`~mwml |am fdic `umwd|icb {y{|mf{ dg`~m( |amwm
dwm {|ihh `|amw fic`w {y{|mf{ |` |`}ka `c# Rm r`c’| b` ic|` bwmd|
lm|dih `c |am{m {y{|mf{( g}| |amy dwm {|ihh r`w|a fmc|i`cicb#
Dfibd k`fu}|mw{ ad~m |amiw `rc Dfibd @[# I| ad{ }cit}m
adwlrdwm ic Dfibd L@[ raika i{ d li{o `umwd|icb {y{|mf# \amiw
ricl`ricb ic|mwndkm i{ kdhhml Ic|}i|i`c( dcl |am bwduaikdh }{mw ic|mwndkm
i{ wmnmwwml |` d{ R`wogmcka# Raihm Dfibd @[ i{c’| d{ u`u}hdw c`r d{
i| }{ml |` gm( |amwm dwm {|ihh {`fm Dfibd k`fu}|mw{ `}| |amwm w}ccicb
|ai{ `umwd|icb {y{|mf#
[`hdwi{ i{ d k`fu}|mw `umwd|icb {y{|mf lm~mh`uml gy [}c
Fikw`{y{|mf{# I| i{ `cm n |am hdwbm{| umc {`}wkm uw`jmk|{ ic |am
k`fu}|mw k`ff}ci|y# I| k`c|ic}m{ | bw`r ic nmd|}wm{( fmfgmw{( dcl
duuhikd|i`c{# I| i{ dc iclmumclmc| `umwd|icb {y{|mf f}ka d{ ]ciq i{
dcl i{ d~dihdghm n`w }{m `c fdcy k`fu}|mw {y{|mf{#
Libi|dh d}li` uhdymw{ w}c `c nwmm {`n|rdwm kdhhml W`kog`q# I| rd{
wmhmd{ml }clmw |am BC] Bmcmwdh U}ghik Hikmc{m# \ai{ i{ d wmhd|i~mhy
cmr `umwd|icb {y{|mf dcl rd{ niw{| ifuhmfmc|ml `c Dwka`{ [|}li`
uhdymw gmkd}{m `n `rcmw nw}{|wd|i`c ri|a hifi|d|i`c{ ic |am
fdc}ndk|}wmw&{}uuhiml }{mw ic|mwndkm dcl lm~ikm `umwd|i`c{# I| i{
uwm{mc| `w d~dihdghm n`w fdcy linnmwmc| uhdymw{ ickh}licb |am cmr `cm{
ri|a f}h|i&k`h`w ~ilm` kdudgihi|im{#
Duuhm K`fu}|mw{ ficid|}wm FU; uhdymw{ w}c `c d ~mw{i`c `n
Hic}q kdhhml iu`l hic}q# Cmrmw uhdymw{ hiom |am iU`l {a}nnhm dwm
{}uu`w|ml gy i|{ `rc ~mw{i`c `n `umwd|icb {y{|mf d{ |am Hic}q {y{|mf
i{c’| kdudghm `n {}uu`w|icb {`fm `n |am cmr bwduaikdh dgihi|im{#
>4
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 62/95
F`{| k`fu}|mw w`}|mw{ w}c `c d Ki{k` umwd|icb {y{|mf# Raihm
|am {umkinik @[ fdy ~dwy {hiba|hy gm|rmmc ~mw{i`c{( |am gd{ik {m|&}u i{
m{{mc|idhhy |am {dfm#
\amwm ad~m gmmc fdcy( fdcy `umwd|icb {y{|mf{ |ad| ad~m gmmc
kwmd|ml `~mw |am ymdw{# \amy ad~m dhh m~`h~ml `~mw |am ymdw{ |`
dkk`ff`ld|m cmr |mkac`h`bim{( dcl |amy rihh k`c|ic}m |ad| m~`h}|i`c
d{ `}w k`fu}|mw{ dcl mhmk|w`cik lm~ikm{ kadcbm#
Ricl`r{ ^i{|d ad{ gmmc |am f`{| wmkmc| @[ |` gm wmhmd{ml# Fdk
rihh {``c gm wmhmd{icb dc`|amw ~mw{i`c `n Fdk @[ Q d{ rmhh l}ggml
‘Hm`udwl‖# D{ |am `umc {`}wkm @[ fdwom| k`c|ic}m{ |` bw`r dcl
m~`h~m( rm dwm hiomhy |` {mm fdcy f`wm `n |am{m u`uuicb }u d{ rmhh#
\am k`fum|i|i`c kdc gm nimwkm# D{ `n hd|m( {`fm }{mw{ ad~m u}|
uwm{{}wm `c Lmhh |` uwm&h`dl dhh `n i|{ UK{ dcl hdu|`u{ ri|a Hic}q
`umwd|icb {y{|mf# Ram|amw `w c`| |ai{ i{ d b``l f`~m wmfdic{ |` gm
{mmc# Fdcy( fdcy k`fu}|mw }{mw{ dwm }{ml |` Ricl`r{( dcl hmdwcicb
d cmr {y{|mf k`}hl gm lm|wifmc|dh |` `cm `n |am hdwbm{| k`fu}|mw
fdc}ndk|}wmw{ ic |am r`whl#
Dc`|amw f`~mfmc| ad{ gmmc |domc `c |` ad~m cmr k`fu}|mw{
k`fm ri|a`}| dc `umwd|icb {y{|mf g}| ri|a d k`}u`c n`w d nwmm @[ `n
|amiw ka``{icb# \ad| rdy( }{mw{ kdc lmkilm n`w |amf{mh~m{ raika
{y{|mf |amy rdc| |` }{m# Fikw`{`n| i{c’| ommc `c |ai{ ilmd( d{ y`} kdc
ifdbicm( g}| rm l` ad~m d nwmm mc|mwuwi{m {y{|mf ic `}w k`}c|wy#
Raihm |amy l` ad~m dc dhf`{| k`wcmw `c |am fdwom|( {`fm gmhim~m |ad|
|am{m `|amw k`fudcim{ {a`}hl gm dghm |` b` dn|mw |amiw ‘uimkm `n |am
uim‖ d{ rmhh#
>7
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 63/95
In y`} |aico y`} rdc| |` kadcbm y`}w k}wwmc| `umwd|icb {y{|mf
`w in y`} ad~m d k`fu}|mw ri|a`}| dc `umwd|icb {y{|mf( y`}’hh cmml |`
oc`r a`r |` ic{|dhh |am cmr @[#
>;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 64/95
IC[\DHHICB DC @UMWD\ICB [Y[\MF
Y`} fiba| |aico |ad| ic{|dhhicb dc `umwd|icb {y{|mf r`}hl gm d
{ifuhm uw`kml}wm# Dcl y`}’l gm wiba|# A`rm~mw( y`} wmdhhy {a`}hl
oc`r rad| y`}’wm l`icb gmn`wm y`} }clmw|dom |ai{ uw`km{{# M~mc in
y`} dhwmdly oc`r a`r |` l` i|( i|’{ dhrdy{ cikm |` ad~m d wmnwm{amw
k`}w{m#
\am niw{| |aicb y`} {a`}hl gmn`wm ic{|dhhicb d cmr `umwd|icb
{y{|mf i{ |` gdko }u y`}w mqi{|icb ld|d# \am{m uw`bwdf{ gd{ikdhhy
|dom d uik|}wm ifdbm `n m~mwy|aicb `c y`}w adwl lwi~m# Ri|a |amf( y`}
kdc wm{|`wm y`}w mc|iwm {y{|mf m~mc in y`}w cmr @[ l`m{c’| hmd~m d|wdkm `n y`}w `hl @[#
\` mnnmk|i~mhy dcl {dnmhy gdko }u y`}w {y{|mf( i|’{ dhrdy{ d b``l
ilmd |` bm| {`fm |yum `n {`n|rdwm uw`bwdf |ad| rihh dkk`fuhi{a |ai{#
Y`} k`}hl |wy l`icb i| y`}w{mhn( g}| |am{m uw`bwdf{ fdom i| f}ka(
f}ka md{imw# K`c{ilmw `cm `n |am n`hh`ricb:
‧ Dkw`ci{ \w}m Ifdbm 45 A`fm
Dkw`ci{ \w}m Ifdbm 45 A`fm kwmd|m{ |am mqdk| k`uy `n y`}w
adwl li{o dcl dhh`r{ y`} |` ic{|dc|hy wm{|`wm |am mc|iwm fdkaicm
ickh}licb `umwd|icb {y{|mf( duuhikd|i`c{( dcl dhh |am ld|d ic |amm~mc| `n d nd|dh {y{|mf kwd{a `w ~iw}{ d||dko “ c` wmic{|dhhd|i`c{
wmt}iwml$
Ri|a |am cmr ~mw{i`c y`} dh{` kdc md{ihy gdko }u y`}w f}{ik(
~ilm`( dcl libi|dh ua`|`{( d{ rmhh d{ @}|h``o m&fdih{( k`c|dk|{(kdhmcldw( |d{o{( dcl }{mw {m||icb{ ri|a j}{| d nmr f`}{m khiko{$
K`uy y`}w mc|iwm UK( ickh}licb |am `umwd|icb {y{|mf(duuhikd|i`c{( }{mw {m||icb{( dcl dhh ld|d }{icb ud|mc|ml li{o
ifdbicb |mkac`h`by? gdko}u y`}w f}{ik( ~ilm`( dcl libi|dhua`|`{? gdko}u y`}w `}|h``o m&fdih{( k`c|dk|{( kdhmcldw( |d{o{(
m|k#? dcl wm{|`wm dhh {m||icb{ n`w Fikw`{`n| @nnikm( i\}cm{( Fmlid
><
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 65/95
Uhdymw( dcl l`zmc{ `n u`u}hdw duuhikd|i`c{#
‧
C`w|`c Ba`{|
Fdlm gy [yfdc|mk K`wu`wd|i`c( |am {dfm um`uhm ra` fdom dcl
li{|wig}|m C`w|`c Dc|i&^iw}{( C`w|`c Ba`{| i{ drdwlicb riccicbgdko&}u {`n|rdwm# Y`} {a`}hl oc`r( a`rm~mw( |ad| |ai{ {`n|rdwm
i{ `chy n`w Fikw`{`n| Ricl`r{ QU dcl 7555 `umwd|icb {y{|mf{#
Hiom \w}m Ifdbm( Ba`{| rihh {d~m m~mwy|aicb `c y`}w k`fu}|mw
{dnmhy dcl mnnikimc|hy# I| rihh gdko }u m~mwy|aicb `c y`}w {y{|mfickh}licb f}{ik( uik|}wm{( duuhikd|i`c{( {m||icb{( m|k# ic `cm md{y
{|mu# I| kdc dh{` wmk`~mw y`}w {y{|mf dcl ld|d m~mc ramc y`}
kdc’| wm{|dw| y`}w `umwd|icb {y{|mf#
‧ [@[ @chicm Gdko}u
Ri|a [@[ @chicm Gdko}u( y`} kdc {|dw| {fdhh( uw`|mk|icb dadcln}h `n wmdhhy ifu`w|dc| nihm{( dcl {kdhm dhh |am rdy }u |`
455BG# I| ommu{ uwm~i`}{ ~mw{i`c{ `n nihm{ n`wm~mw# Dclk`c|ic}`}{ gdko}u fmdc{ y`}w nihm{ dwm dhrdy{ gdkoml }u#
I| adclhm{ `umc nihm{ dcl umwn`wf{ k`c|ic}`}{ dcl {kaml}hmlgdko}u# [@[ gdko{ }u `chy linnmwmckm{ n`w kadcbml nihm{ dcl
{|`wm{ }chifi|ml ~mw{i`c{# I| dh{` ad{ `chicm dkkm{{ dcl nihm{adwicb#
D nwmm |widh ~mw{i`c kdc gm l`rch`dlml d|a||u://rrr#{`{`chicmgdko}u#k`f/
‧ Ba`{| n`w Hic}q
In y`} dwm k}wwmc|hy }{icb Hic}q n`w y`}w `umwd|icb {y{|mf dclrdc| |` {ri|ka |` dc`|amw `cm( |ai{ i{ |am uw`bwdf n`w y`}# Hiom
`|amw gdko}u {`n|rdwm uw`bwdf{( Ba`{| n`w Hic}q i{ d kh`cicb|``h dcl rd{ kwmd|ml gy [yfdc|mk( |am n`ho{ ra` gw`}ba| }{
C`w|`c Dc|i&^iw}{#
Y`}w lwi~m rihh gm kh`cml }{icb |am khiko dcl kh`cm |``h# I| ad{
>=
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 66/95
gmmc {dil |` gm md{y |` }{m dcl ~mwy mnnikimc|#
@ckm y`} ad~m dhh `n y`}w nihm{ gdkoml }u dcl y`} dwm {}wm |am
li{o k`c|dic{ dhh `n y`}w icn`wfd|i`c( y`}’hh |amc gm wmdly |` ic{|dhhy`}w {y{|mf# \ai{ i{ |am md{im{| uw`km{{ `n dhh#
In y`} ad~m u}wkad{ml dc @[ {}ka d{ Ricl`r{( i| rihh k`fm ri|adc ic{|dhhd|i`c li{o# Rad| y`}’hh cmml |` l` i{ u}| |am li{o ic y`}w li{o
lwi~m dcl |amc {a}| l`rc y`}w k`fu}|mw# \}wc i| gdko c( dcl |am @[
rihh gmbic ic{|dhhicb nw`f |am g``|# N`hh`r dcy `c&{kwmmc uw`fu|{ dcldc{rmw dkk`wlicbhy#
In y`} ad~m l`rch`dlml y`}w cmr @[ nw`f d nwmmrdwm {i|m {}kad{ |a`{m |ad| `nnmw Hic}q n`w nwmm( y`} rihh cmml |` {d~m |am uw`bwdf |`
y`}w k`fu}|mw’{ ‘Fy L`k}fmc|{‖ dwmd# @ckm i| ad{ l`rch`dlml( b` |` ‘Fy L`k}fmc|{‖ dcl l`}ghm khiko `c |am nihm# Y`} rihh uw`gdghy |amc
gm liwmk|ml |` dc{rmw t}m{|i`c{ d{ |` a`r |` uw`kmml#
Gm drdwm |ad| |am ic{|dhhd|i`c uw`km{{ rihh uw`gdghy |dom {`fm|ifm |` k`fuhm|m# Y`} cmml |` f`ci|`w |am uw`bwm{{( {` mqumk| |`
{umcl d| hmd{| dc a`}w l}wicb |am ic{|dhh dc{rmwicb t}m{|i`c{ dclrd|kaicb i| ic{|dhh#
@ckm y`}w cmr {y{|mf i{ ic{|dhhml( y`} {a`}hl {umcl {`fm |ifmb`icb |aw`}ba i|{ nmd|}wm{ dcl umwn`wficb |d{o{ |ad| y`} r`}hl
c`wfdhhy l`# Fdom {}wm |ad| dhh y`}w uwm~i`}{ n}ck|i`c{ r`wo# Ommu ic
ficl |ad| in y`} ad~m adl kmw|dic uw`bwdf{ dcl duuhikd|i`c{ `c y`}wk`fu}|mw uwi`w |` |am wm&ic{|dhh( y`} rihh ad~m |` u}| |amf gdko `c
dn|mw |am ic{|dhh#
N`w mqdfuhm( in y`} adl d nd~`wi|m bdfm `c |am k`fu}|mw gmn`wm(y`} rihh ad~m h`{| i| ri|a |am wm&g``|# Y`} rihh ad~m |` wm&ic{|dhh |ambdfm in y`} rdc| |` uhdy i|#
\ad|’{ i| n`w ic{|dhhicb dc `umwd|icb {y{|mf# I| wmdhhy i{ t}i|m d{ifuhm uw`km{{( g}| i| kdc gm |ifm k`c{}ficb( {` gm uwmudwml gmn`wm
y`} uw`kmml$
>>
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 67/95
C`r hm|’{ |dom d h``o d| {`fm `n |am n}ck|i`c{ k`c|dicml ic dc
`umwd|icb {y{|mf dcl rad| |amy fmdc# [`fm|ifm{ k`fu}|mw
|mwfic`h`by kdc gm d gi| k`cn}{icb( {` i|’{ amhun}h |` oc`r rad| kmw|dic
n}ck|i`c{ dwm dhh dg`}|$
LMNICICB \AM UW@KM[[M[
Kdkam
Ramc {a`uuicb n`w d k`fu}|mw( `n|mc |am r`wl ‘kdkam‖ rihh
k`fm }u# \amwm dwm |r` |yum{ `n kdkam{ ramc i| k`fm{ |` f`lmwc
>2
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 68/95
k`fu}|mw{: H4 dcl H7# [`fm c`r m~mc ad~m H; kdkam{# Kdkaicb i{ d
~mwy ifu`w|dc| uw`km{{ ramc i| k`fm{ |` y`}w UK#
\amwm dwm fmf`wy kdkam{( adwlrdwm dcl {`n|rdwm li{o kdkam{(
udbm kdkam{ dcl f`wm# ^iw|}dh fmf`wy i{ m~mc d n`wf `n kdkaicb#
Hm|’{ h``o d| rad| kdkaicb i{ dcl ray i| i{ {` ifu`w|dc|#
Kdkaicb i{ d |mkac`h`by gd{ml `c |am fmf`wy {}g{y{|mf `n
y`}w k`fu}|mw# \am fdic u}wu`{m `n d kdkam i{ |` dkkmhmwd|m y`}w
k`fu}|mw raihm ommuicb |am uwikm `n |am k`fu}|mw h`r# Kdkaicb dhh`r{
y`} |` l` y`}w k`fu}|mw |d{o{ f`wm wduilhy#
\` }clmw{|dcl |am gd{ik ilmd gmaicl d kdkam {y{|mf( rm kdc
}{m d {ifuhm dcdh`by }{icb d higwdwidc |` lmf`c{|wd|m |am kdkaicb
uw`km{{# \aico `n d higwdwidc gmaicl |am lm{o# Am `w {am i{ |amwm |
bi~m y`} |am g``o{ y`} d{o n`w#
\` ommu i| {ifuhm( hm|’{ d{{}fm |ad| y`} kdc’| bm| |am g``o{y`}w{mhn( y`} ad~m |` d{o |am higwdwidc n`w |am g``o y`} rdc| |` wmdl
dcl am `w {am bm|{ i| n`w nw`f y`} nw`f {amh~icb ic d {|`wmw `f# \ai{
niw{| mqdfuhm i{ d higwdwidc ri|a`}| d kdkam#
\am niw{| umw{`c dwwi~m{ dcl d{o{ n w |am g``o Bwmd| Mqumk|d|i`c{# \am
higwdwidc b`m{ |` |am {|`wmw``f( bm|{ |am g``o( wm|}wc{ |` |am k`}c|mw(
dcl bi~m{ |am g``o |` |am k}{|`fmw# Hd|mw( |am g ww`rmw k`fm{ gdko
|` wm|}wc |am g``o# \am higwdwidc |dom{ |am g``o dcl wm|}wc{ i| |` |am
{|`wmw``f wm|}wcicb |` |am k`}c|mw |` rdi| n`w |am cmq| k}{|`fmw#
\am cmq| k}{|`fmw k`fm{ ic dcl dh{` d{o{ n`w Bwmd|
>1
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 69/95
Mqumk|d|i`c{# \am higwdwidc ad{ |` wm|}wc |` |am {|`wmw``f |` bm| |am
{dfm g``o am adl dhwmdly adclhml dcl bi~m i| |` |am khimc|# [`
gd{ikdhhy( |am higwdwidc ad{ |` fdom d k`fuhm|m w`}cl |wiu |` nm|ka
m~mwy g``o ‛ m~mc ~mwy u`u}hdw `cm{ |ad| dwm wmt}m{|ml nwmt}mc|hy#
\ai{ i{c’| d ~mwy mnnikimc| {y{|mf n`w `}w higwdwidc( i{ i|0
A`rm~mw( |amwm i{ d rdy |` ifuw`~m `c |ai{ {y{|mf# Rm kdc dll d
kdkam `c |am higwdwidc#
\` ihh}{|wd|m d kdkam( hm|’{ bi~m |am higwdwidc d gdkoudko ic|`
raika am `w {am rihh gm dghm |` {|`wm( {dy( |mc g``o{# \ad| r`}hl
fmdc |am higwdwidc ad{ d 45 g``o kdkam# Ic |ai{ gdkoudko( am w {am
rihh u}| |am g``o{ |am k}{|`fmw{ wm|}wc |` aif }u |` d fdqif}f `n
|mc# C`r( hm|’{ b` gdko dcl ~i{i| |am niw{| {kmcdwi` ri|a `}w kdkaml
higwdwidc#
D| |am gmbiccicb `n |am ldy( |am higwdwidc’{ kdkam i{ mfu|y# \am
niw{| umw{`c dwwi~m{ dcl d{o{ n`w Bwmd| Mqumk|d|i`c{# [` |am higwdwidcb`m{ |` |am {|`wmw``f dcl bi~m{ i| |` |am k}{|`fmw# Ramc |am
k}{|`fmw wm|}wc ri|a |am g``o( ic{|mdl `n b`icb gdko |` |am
{|`wmw``f( |am higwdwidc u}|{ |am g``o ic|` |am gdkoudko fdoicb {}wm
i| i{c’| n}hh niw{|#
Dc`|amw umw{`c dwwi~m{ dcl d{o{ n`w Bwmd| Mqumk|d|i`c{# Gmn`wm
b`icb |` |am {|`wmw``f |am higwdwidc kamko{ |` {mm in |am g``o i{ ic |am
gdkoudko dhwmdly# H` dcl gma`hl( i| i{$ C`r dhh am `w {am ad{ |` l` i{
|dom |am g``o nw`f |am gdkoudko dcl bi~m i| |` |am khimc|# C` mq|wd
mcmwby i{ mqumclml gy |am higwdwidc( dcl |am k}{|`fmw l`m{c’| ad~m |`
rdi| n`w |ad| |wiu |` |am {|`wmw``f#
>9
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 70/95
Hm|’{ d{{}fm |ad| |am k}{|`fmw d{o{ n`w d |i|hm |ad|’{ c`| ic |am
gdkoudko0 Ic |ai{ kd{m( |am higwdwidc i{ hm{{ mnnikimc| ri|a d kdkam
gmkd}{m am `w {am f}{| |dom |am |ifm |` h``o n`w |am g``o ic |am
gdkoudko niw{|#
\ad| i{ ray `cm `n |am kadhhmcbm{ `n kdkam lm{ibc i{ |` ficifizm
|am ifudk| `n kdkam {mdwkam{# F`lmwc adwlrdwm ad{ wml}kml |ai{ |ifm
lmhdy |` uwdk|ikdhhy zmw # \am |ifm i| |dom{ n`w |am higwdwidc |` h``o ic
|am kdkam i{ f}ka hm{{ |adc ad~icb |` w}c |` |am {|`wmw``f( {` |ifm i{
{d~ml d}|`fd|ikdhhy ri|a d kdkam# \am kdkam i{ {fdhh !j}{| |mc g``o{)
{` |am |ifm i| |dom{ |` c`|ikm d fi{{ i{ `chy d |icy nwdk|i`c `n |am |ifm i|
|dom{ |` rdho |` |am {|`wmw``f#
Nw`f |ai{ mqdfuhm y`} kdc {mm {m~mwdh ifu`w|dc| ndk|{ dg`}|
kdkaicb:
‧ Kdkam |mkac`h`by i{ |am }{m `n d nd{|mw g}| {fdhhmw fmf`wy
|yum |` dkkmhmwd|m d {h`rmw g}| hdwbmw fmf`wy |yum#
‧ Ramc }{icb d kdkam( y`} f}{| kamko |am kdkam |` {mm in dc
i|mf i{ ic |amwm# In i| i{ |amwm( i|"{ kdhhml d kdkam ai|# In c`|( i| i{
kdhhml d kdkam fi{{ dcl |am k`fu}|mw f}{| rdi| n`w d w`}cl |wiu
nw`f |am hdwbmw( {h`rmw fmf`wy dwmd#
‧ D kdkam ad{ {`fm fdqif}f {izm |ad| i{ f}ka {fdhhmw |adc
|am hdwbmw {|`wdbm dwmd#
25
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 71/95
‧ I| i{ u`{{ighm |` ad~m f}h|iuhm hdymw{ `n kdkam# Ri|a `}w
higwdwidc mqdfuhm( |am {fdhhmw g}| nd{|mw fmf`wy |yum i{ |am
gdkoudko( dcl |am {|`wmw``f wmuwm{mc|{ |am hdwbmw dcl {h`rmw
fmf`wy |yum# \ai{ i{ d `cm&hm~mh kdkam#
\amwm fiba| gm dc`|amw hdymw `n kdkam k`c{i{|icb `n d {amhn |ad| kdc
a`hl 455 g``o{ gmaicl |am k`}c|mw# \am higwdwidc kdc kamko |am
gdkoudko( |amc |am {amhn dcl |amc |am {|`wmw``f# \ai{ r`}hl gm d
|r`&hm~mh kdkam#
D k`fu}|mw i{ d fdkaicm ic raika rm fmd{}wm |ifm ic ~mwy {fdhh
ickwmfmc|{# Ramc |am fikw`uw`km{{`w dkkm{{m{ |am fdic fmf`wy
!WDF)( i| l`m{ i| ic dg`}| >5 cdc`{mk`cl{ !>5 gihhi`c|a{ `n d {mk`cl)#
\ad|"{ uwm||y nd{|( g}| i| i{ f}ka {h`rmw |adc |am |yuikdh
fikw`uw`km{{`w# Fikw`uw`km{{`w{ kdc ad~m kykhm |ifm{ d{ {a`w| d{ 7
cdc`{mk`cl{( {` |` d fikw`uw`km{{`w >5 cdc`{mk`cl{ {mmf{ hiom dc
m|mwci|y#
Rad| in rm g}ihl d {umkidh fmf`wy gdco ic |am f`|amwg`dwl(
{fdhh g}| ~mwy nd{| !dw`}cl ;5 cdc`{mk`cl{)0 \ad|"{ dhwmdly |r` |ifm{
nd{|mw |adc |am fdic fmf`wy dkkm{{# \ad|"{ kdhhml d hm~mh 7 kdkam `w
dc H7 kdkam#
Rad| in rm g}ihl dc m~mc {fdhhmw g}| nd{|mw fmf`wy {y{|mf
liwmk|hy ic|` |am fikw`uw`km{{`w"{ kaiu0 \ad| rdy( |ai{ fmf`wy rihh gm
dkkm{{ml d| |am {umml `n |am fikw`uw`km{{`w dcl c`| |am {umml `n |am
fmf`wy g}{# \ad|"{ dc H4 kdkam( raika `c d 7;;&fmbdamw|z !FAz)
Umc|i}f i{ ;#= |ifm{ nd{|mw |adc |am H7 kdkam( raika i{ |r` |ifm{
24
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 72/95
nd{|mw |adc |am dkkm{{ |` fdic fmf`wy#
[`fm fikw`uw`km{{`w{ ad~m |r` hm~mh{ `n kdkam g}ih| wiba| ic|`
|am kaiu# Ic |ai{ kd{m( |am f`|amwg`dwl kdkam && |am kdkam |ad| mqi{|{
gm|rmmc |am fikw`uw`km{{`w dcl fdic {y{|mf fmf`wy && gmk`fm{
hm~mh ;( `w H; kdkam#
\amwm dwm d h`| `n {}g{y{|mf{ ic d k`fu}|mw? y`} kdc u}| kdkam
gm|rmmc fdcy `n |amf |` ifuw`~m umwn`wfdckm# Amwm"{ dc mqdfuhm#
Rm ad~m |am fikw`uw`km{{`w !|am nd{|m{| |aicb ic |am k`fu}|mw)# \amc
|amwm"{ |am H4 kdkam |ad| kdkam{ |am H7 kdkam |ad| kdkam{ |am fdic
fmf`wy raika kdc gm }{ml !dcl i{ `n|mc }{ml) d{ d kdkam n`w m~mc
{h`rmw umwiuamwdh{ hiom adwl li{o{ dcl KL&W@F{# \am adwl li{o{ dwm
dh{` }{ml |` kdkam dc m~mc {h`rmw fmli}f && y`}w Ic|mwcm|
k`ccmk|i`c#
Y`}w Ic|mwcm| k`ccmk|i`c i{ |am {h`rm{| hico ic y`}w k`fu}|mw# [`
y`}w gw`r{mw !Ic|mwcm| Mquh`wmw( Cm|{kdum( m|k#) }{m{ |am adwl li{o |`
{|`wm A\FH udbm{( u}||icb |amf ic|` d {umkidh n`hlmw `c y`}w li{o#
\am niw{| |ifm y`} d{o n`w dc A\FH udbm( y`}w gw`r{mw wmclmw{ i|
dcl d k`uy `n i| i{ dh{` {|`wml `c y`}w li{o# \am cmq| |ifm y`} wmt}m{|
dkkm{{ |` |ai{ udbm( y`}w gw`r{mw kamko{ in |am ld|m `n |am nihm `c |am
Ic|mwcm| i{ cmrmw |adc |am `cm kdkaml# In |am ld|m i{ |am {dfm( y`}w
gw`r{mw }{m{ |am `cm `c y`}w adwl li{o ic{|mdl `n l`rch`dlicb i| nw`f
Ic|mwcm|# Ic |ai{ kd{m( |am {fdhhmw g}| nd{|mw fmf`wy {y{|mf i{ y`}w
adwl li{o dcl |am hdwbmw dcl {h`rmw `cm i{ |am Ic|mwcm|#
27
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 73/95
Kdkam kdc dh{` gm g}ih| liwmk|hy `c umwiuamwdh{# F`lmwc adwl
li{o{ k`fm ri|a nd{| fmf`wy( dw`}cl =47 oih`gy|m{( adwlriwml |` |am
adwl li{o# \am k`fu}|mw l`m{c"| liwmk|hy }{m |ai{ fmf`wy && |am adwl&
li{o k`c|w`hhmw l`m{#
N`w |am k`fu}|mw( |am{m fmf`wy kaiu{ dwm |am li{o i|{mhn# \am
k`fu}|mw d{o{ n`w ld|d nw`f |am adwl li{o# \am adwl&li{o k`c|w`hhmw
kamko{ ic|` |ai{ fmf`wy uwi`w |` f`~icb |am fmkadcikdh udw|{ `n |am
adwl li{o# \ai{ i{ ~mwy {h`r k`fudwml |` fmf`wy# In i| nicl{ |am ld|d
|ad| |am k`fu}|mw d{oml n`w ic |am kdkam( i| rihh wm|}wc |am ld|d {|`wml
ic |am kdkam ri|a`}| dk|}dhhy dkkm{{icb ld|d `c |am li{o i|{mhn( {d~icb d
h`| `n |ifm#
Amwm"{ dc mqumwifmc| y`} kdc |wy# Y`}w k`fu}|mw kdkam{ y`}w
nh`uuy lwi~m ri|a fdic fmf`wy( dcl y`} kdc dk|}dhhy {mm i| aduumcicb#
Dkkm{{ d hdwbm nihm nw`f y`}w nh`uuy && n`w mqdfuhm( `umc d ;55&
oih`gy|m |mq| nihm ic d |mq| mli|`w#
\am niw{| |ifm( y`} rihh {mm |am hiba| `c y`}w nh`uuy |}wcicb `c(
dcl y`} rihh rdi|# \am nh`uuy li{o i{ mq|wmfmhy {h`r( {` i| rihh |dom 75
{mk`cl{ |` h`dl |am nihm# C`r( kh`{m |am mli|`w dcl `umc |am {dfm nihm
dbdic# \am {mk`cl |ifm !l`c"| rdi| ;5 fic}|m{ `w l` d h`| `n li{o
dkkm{{ gm|rmmc |am |r` |wim{) y`} r`c"| {mm |am hiba| |}wcicb `c( dcl
y`} r`c"| rdi|#
\am `umwd|icb {y{|mf kamkoml ic|` i|{ fmf`wy kdkam n`w |am
nh`uuy li{o dcl n`}cl rad| i| rd{ h``oicb n`w# [` ic{|mdl `n rdi|icb 75
{mk`cl{( |am ld|d rd{ n`}cl ic d fmf`wy {}g{y{|mf f}ka nd{|mw |adc
ramc y`} niw{| |wiml i|# @cm dkkm{{ |` |am nh`uuy li{o |dom{ 475
2;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 74/95
fihhi{mk`cl{( raihm `cm dkkm{{ |` |am fdic fmf`wy |dom{ dw`}cl >5
cdc`{mk`cl{ && |ad|"{ d h`| nd{|mw# Y`} k`}hl ad~m w}c |am {dfm |m{| `c
y`}w adwl li{o( g}| i|"{ f`wm m~ilmc| `c |am nh`uuy lwi~m gmkd}{m i|"{
{` {h`r#
\` bi~m y`} |am gib uik|}wm `n i| dhh( amwm"{ d hi{| `n d c`wfdh
kdkaicb {y{|mf:
‧ H4 kdkam & Fmf`wy dkkm{{m{ d| n}hh fikw`uw`km{{`w {umml !45
cdc`{mk`cl{( < oih`gy|m{ |` 4> oih`gy|m{ ic {izm)
‧ H7 kdkam & Fmf`wy dkkm{{ `n |yum [WDF !dw`}cl 75 |` ;5
cdc`{mk`cl{( 471 oih`gy|m{ |` =47 oih`gy|m{ ic {izm)
‧ Fdic fmf`wy & Fmf`wy dkkm{{ `n |yum WDF !dw`}cl >5
cdc`{mk`cl{( ;7 fmbdgy|m{ |` 471 fmbdgy|m{ ic {izm)
‧ Adwl li{o & Fmkadcikdh( {h`r !dw`}cl 47 fihhi{mk`cl{( 4
bibdgy|m |` 45 bibdgy|m{ ic {izm)
‧ Ic|mwcm| & Ickwmlighy {h`r !gm|rmmc 4 {mk`cl dcl ; ldy{(
}chifi|ml {izm)
D{ y`} kdc {mm( |am H4 kdkam kdkam{ |am H7 kdkam( raika kdkam{
|am fdic fmf`wy( raika kdc gm }{ml |` kdkam |am li{o {}g{y{|mf{(
dcl {` `c#
2<
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 75/95
@cm k`ff`c t}m{|i`c d{oml d| |ai{ u`ic| i{( 'Ray c`| fdom dhh
`n |am k`fu}|mw"{ fmf`wy w}c d| |am {dfm {umml d{ |am H4 kdkam( {`
c` kdkaicb r`}hl gm wmt}iwml0' \ad| r`}hl r`wo( g}| i| r`}hl gm
ickwmlighy mqumc{i~m# \am ilmd gmaicl kdkaicb i{ |` }{m d {fdhh df`}c|
`n mqumc{i~m fmf`wy |` {umml }u d hdwbm df`}c| `n {h`rmw( hm{{&
mqumc{i~m fmf`wy#
Ic lm{ibcicb d k`fu}|mw( |am b`dh i{ |` dhh`r |am fikw`uw`km{{`w
|` w}c d| i|{ n}hh {umml d{ icmqumc{i~mhy d{ u`{{ighm# D =55&FAz kaiu
b`m{ |aw`}ba =55 fihhi`c kykhm{ ic `cm {mk`cl !`cm kykhm m~mwy |r`
cdc`{mk`cl{)# Ri|a`}| H4 dcl H7 kdkam{( dc dkkm{{ |` |am fdic
fmf`wy |dom{ >5 cdc`{mk`cl{( `w dg`}| ;5 rd{|ml kykhm{ dkkm{{icb
fmf`wy#
Ramc y`} |aico dg`}| i|( i| i{ oicl `n ickwmlighm |ad| {}ka
wmhd|i~mhy |icy df`}c|{ `n fmf`wy kdc fdqifizm |am }{m `n f}ka
hdwbmw df`}c|{ `n fmf`wy# \aico dg`}| d 7=>&oih`gy|m H7 kdkam |ad|
kdkam{ >< fmbdgy|m{ `n WDF# Ic |ai{ kd{m( 7=>(555 gy|m{ mnnikimc|hy
kdkam{ ><(555(555 gy|m{# Ray l`m{ |ad| r`wo0
Ic k`fu}|mw {kimckm( |amwm i{ d |am`wm|ikdh k`ckmu| kdhhml h`kdhi|y
`n wmnmwmckm# I| fmdc{ |ad| ic d ndiwhy hdwbm uw`bwdf( `chy {fdhh
u`w|i`c{ dwm m~mw }{ml d| dcy `cm |ifm# D{ {|wdcbm d{ i| fdy {mmf(
h`kdhi|y `n wmnmwmckm r`wo{ n`w |am a}bm fdj`wi|y `n uw`bwdf{# M~mc in |am mqmk}|dghm i{ 45 fmbdgy|m{ ic {izm( `chy d adcln}h `n gy|m{ nw`f
|ad| uw`bwdf dwm ic }{m d| dcy `cm |ifm( dcl |amiw wd|m `n wmum|i|i`c i{
~mwy aiba#
2=
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 76/95
^iw|}dh Fmf`wy
^iw|}dh fmf`wy i{ d k`ff`c udw| `n f`{| `umwd|icb {y{|mf{ `c
lm{o|`u k`fu}|mw{# I| ad{ gmk`fm {` k`ff`c gmkd}{m i| uw`~ilm{ d
gib gmcmni| n`w }{mw{ d| d ~mwy h`r k`{|#
F`{| k`fu}|mw{ |`ldy ad~m {`fm|aicb hiom ;7 `w >< fmbdgy|m{
`n WDF d~dihdghm n`w |am KU] |` }{m# ]cn`w|}cd|mhy( |ad| df`}c| `n
WDF i{ c`| mc`}ba |` w}c dhh `n |am uw`bwdf{ |ad| f`{| }{mw{ mqumk|
|` w}c d| `ckm#
N`w mqdfuhm( in y`} h`dl |am `umwd|icb {y{|mf( dc m&fdih
uw`bwdf( d Rmg gw`r{mw dcl r`wl uw`km{{`w ic|` WDF {if}h|dcm`}{hy(
;7 fmbdgy|m{ i{ c`| mc`}ba |` a`hl i| dhh# In |amwm rmwm c` {}ka |aicb
d{ ~iw|}dh fmf`wy( |amc `ckm y`} nihhml }u |am d~dihdghm WDF y`}w
k`fu}|mw r`}hl ad~m |` {dy( '[`wwy( y`} kdc c`| h`dl dcy f`wm
duuhikd|i`c{# Uhmd{m kh`{m dc`|amw duuhikd|i`c |` h`dl d cmr `cm#' Ri|a
~iw|}dh fmf`wy( rad| |am k`fu}|mw kdc l` i{ h``o d| WDF n`w dwmd{
|ad| ad~m c`| gmmc }{ml wmkmc|hy dcl k`uy |amf `c|` |am adwl li{o#
\ai{ nwmm{ }u {udkm ic WDF |` h`dl |am cmr duuhikd|i`c#
Gmkd}{m |ai{ k`uyicb aduumc{ d}|`fd|ikdhhy( y`} l`c"| m~mc
oc`r i| i{ aduumcicb( dcl i| fdom{ y`}w k`fu}|mw nmmh hiom i{ ad{
}chifi|ml WDF {udkm m~mc |a`}ba i| `chy ad{ ;7 fmbdgy|m{ ic{|dhhml#
Gmkd}{m adwl li{o {udkm i{ {` f}ka kamdumw |adc WDF kaiu{( i| dh{`
ad{ d cikm mk`c`fik gmcmni|#
2>
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 77/95
\am wmdl/rwi|m {umml `n d adwl lwi~m i{ f}ka {h`rmw |adc WDF(
dcl |am |mkac`h`by `n d adwl lwi~m i{ c`| bmdwml |`rdwl dkkm{{icb
{fdhh uimkm{ `n ld|d d| d |ifm# In y`}w {y{|mf ad{ |` wmhy |`` amd~ihy
`c ~iw|}dh fmf`wy( y`} rihh c`|ikm d {ibcinikdc| umwn`wfdckm lw`u# \am
omy i{ |` ad~m mc`}ba WDF |` adclhm m~mwy|aicb y`} |mcl |` r`wo `c
{if}h|dcm`}{hy && |amc( |am `chy |ifm y`} 'nmmh' |am {h`rcm{{ `n ~iw|}dh
fmf`wy i{ i{ ramc |amwm"{ d {hiba| ud}{m ramc y`}"wm kadcbicb |d{o{#
Ramc |ad|"{ |am kd{m( ~iw|}dh fmf`wy i{ umwnmk|#
Ramc i| i{ c`| |am kd{m( |am `umwd|icb {y{|mf ad{ |` k`c{|dc|hy
{rdu icn`wfd|i`c gdko dcl n`w|a gm|rmmc WDF dcl |am adwl li{o# \ai{
i{ kdhhml |awd{aicb( dcl i| kdc fdom y`}w k`fu}|mw nmmh ickwmlighy {h`r#
\am dwmd `n |am adwl li{o |ad| {|`wm{ |am WDF ifdbm i{ kdhhml d
udbm nihm# I| a`hl{ udbm{ `n WDF `c |am adwl li{o( dcl |am `umwd|icb
{y{|mf f`~m{ ld|d gdko dcl n`w|a gm|rmmc |am udbm nihm dcl WDF# @c
d Ricl`r{ fdkaicm( udbm nihm{ ad~m d #[RU mq|mc{i`c#
Ricl`r{ 91 i{ dc mqdfuhm `n d |yuikdh `umwd|icb {y{|mf |ad| ad{
~iw|}dh fmf`wy# Ricl`r{ 91 ad{ dc ic|mhhibmc| ~iw|}dh fmf`wy
fdcdbmw |ad| }{m{ d lmnd}h| {m||icb |` amhu Ricl`r{ dhh`kd|m adwl
lwi~m {udkm n`w ~iw|}dh fmf`wy d{ cmmlml# N`w f`{| kiwk}f{|dckm{(
|ai{ {a`}hl fmm| y`}w cmml{( g}| y`} fdy rdc| |` fdc}dhhy k`cnib}wm
~iw|}dh fmf`wy( m{umkidhhy in y`} ad~m f`wm |adc `cm uay{ikdh adwl
lwi~m `w {umml&kwi|ikdh duuhikd|i`c{#
22
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 78/95
[y{|mf Wm{`}wkm{
Fdcy um`uhm kdc bm| k`cn}{ml dg`}| w}ccicb `}| `n ‘fmf`wy‖
ramc |amy bm| |am fm{{dbm |ad| |am {y{|mf wm{`}wkm{ dwm `}| `n fmf`wy# Ic fdcy kd{m{( dc '`}| `n fmf`wy' fm{{dbm i{ fi{hmdlicb(
{ickm y`}w ra`hm {y{|mf wmdhhy lil c`| w}c `}| `n fmf`wy# Rad| |ai{
wmdhhy fmdc{ i{ |ad| kmw|dic {y{|mf{ ic y`}w k`fu}|mw dwm w}ccicb h`r
`c fmf`wy#
Ricl`r{ fdic|dic{ dc dwmd `n fmf`wy n`w `umwd|icb {y{|mf
wm{`}wkm{# \am fdqif}f {izm `n |ai{ dwmd i{ 471O( ic |r` ><O dwmd{#
Ricl`r{ }{m{ |ai{ dwmd `n fmf`wy |` {|`wm n`c|{( gi|fdu{( lw`u&l`rc
fmc} hi{|{ dcl `|amw `c&{kwmmc icn`wfd|i`c }{ml gy mdka duuhikd|i`c#
Ramc dcy uw`bwdf gmbic{ w}ccicb( i| }{m{ }u {`fm {udkm ic |am
'{y{|mf wm{`}wkm{' dwmd ic fmf`wy# G}|( d{ y`} mqi|( {`fm uw`bwdf{
l` c`| bi~m gdko {y{|mf wm{`}wkm{ |amy rmwm |mfu`wdwihy }{icb#
M~mc|}dhhy |am {y{|mf rihh kwd{a d{ i| w}c{ `}| `n fmf`wy# \am kwd{a
aduumc{ {`fm|ifm{ in y`} {|dw| dcl kh`{m fdcy uw`bwdf{( m~mc |am
{dfm `cm{( ri|a`}| d umwi`lik wmg``|# \ai{ i{ rad| Fikw`{`n| kdhh{ d
wm{`}wkm hmdo `w fmf`wy hmdo#
Ramc y`} |mhh y`}w {y{|mf |` mqi| d uw`bwdf( |am uw`bwdf i{
{}uu`{ml |` bi~m gdko |am wm{`}wkm{ !fmf`wy) i| rd{ }{icb# A`rm~mw(uw`bwdf{ dwm rwi||mc gy a}fdc{ dcl fi{|dom{ kdc aduumc# \am
uw`bwdf fdy c`| bi~m gdko dhh `n |am wm{`}wkm{ |` |am `umwd|icb
{y{|mf# \ai{ ndihicb |` 'bi~m gdko' i{ |am 'fmf`wy hmdo(' m~mc|}dhhy
hmdlicb |` d fm{{dbm |ad| y`}w k`fu}|mw i{ h`r `c wm{`}wkm{# Fmf`wy
21
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 79/95
hmdo{ kdc dh{` gm kd}{ml gy uw`bwdf{ |ad| d}|`fd|ikdhhy h`dl m~mwy
|ifm y`} g``| y`}w {y{|mf#
\am {y{|mf wm{`}wkm{ uw`ghmf i{ {`fm|aicb y`} fiba| ad~m |`
hi~m ri|a }c|ih |am fi{gmad~icb duuhikd|i`c i{ n`}cl# In y`} dwm {}wm d
kmw|dic duuhikd|i`c i{ kd}{icb |am uw`ghmf( gm {}wm |` k`c|dk| |am
{`n|rdwm ~mcl`w#
\am gm{| uwm~mc|i~m fdic|mcdckm i{ |` umwi`likdhhy wmg``| y`}w
{y{|mf#
WDF
Wdcl`f dkkm{{ fmf`wy !WDF) i{ |am gm{| oc`rc n`wf `n
k`fu}|mw fmf`wy# WDF i{ k`c{ilmwml 'wdcl`f dkkm{{' gmkd}{m y`}
kdc dkkm{{ dcy fmf`wy kmhh liwmk|hy in y`} oc`r |am w`r dcl k`h}fc
|ad| ic|mw{mk| d| |ad| kmhh#
\am `uu`{i|m `n WDF i{ {mwidh dkkm{{ fmf`wy ![DF)# [DF {|`wm{
ld|d d{ d {mwim{ `n fmf`wy kmhh{ |ad| kdc `chy gm dkkm{{ml
{mt}mc|idhhy !hiom d kd{{m||m |dum)#
In |am ld|d i{ c`| ic |am k}wwmc| h`kd|i`c( mdka fmf`wy kmhh i{
kamkoml }c|ih |am cmmlml ld|d i{ n`}cl# [DF r`wo{ ~mwy rmhh n`w
fmf`wy g}nnmw{( ramwm |am ld|d i{ c`wfdhhy {|`wml ic |am `wlmw ic
raika i| rihh gm }{ml !d b``l mqdfuhm i{ |am |mq|}wm g}nnmw fmf`wy `c
29
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 80/95
d ~ilm` kdwl)# WDF ld|d( `c |am `|amw adcl( kdc gm dkkm{{ml ic dcy
`wlmw#
[ifihdw |` d fikw`uw`km{{`w( d fmf`wy kaiu i{ dc ic|mbwd|ml
kiwk}i| !IK) fdlm `n fihhi`c{ `n |wdc{i{|`w{ dcl kdudki|`w{# Ic |am f`{|
k`ff`c n`wf `n k`fu}|mw fmf`wy( lycdfik wdcl`f dkkm{{ fmf`wy
!LWDF)( d |wdc{i{|`w dcl d kdudki|`w dwm udiwml |` kwmd|m d fmf`wy
kmhh( raika wmuwm{mc|{ d {icbhm gi| `n ld|d#
\am kdudki|`w a`hl{ |am gi| `n icn`wfd|i`c && d 5 `w d 4# \am
|wdc{i{|`w dk|{ d{ d {ri|ka |ad| hm|{ |am k`c|w`h kiwk}i|wy `c |am fmf`wy
kaiu wmdl |am kdudki|`w `w kadcbm i|{ {|d|m#
D kdudki|`w i{ hiom d {fdhh g}kom| |ad| i{ dghm |` {|`wm mhmk|w`c{#
\` {|`wm d 4 ic |am fmf`wy kmhh( |am g}kom| i{ nihhml ri|a mhmk|w`c{# \`
{|`wm d 5( i| i{ mfu|iml# \am uw`ghmf ri|a |am kdudki|`w"{ g}kom| i{ |ad|
i| ad{ d hmdo# Ic d fd||mw `n d nmr fihhi{mk`cl{ d n}hh g}kom| gmk`fm{
mfu|y#
\amwmn`wm( n`w lycdfik fmf`wy |` r`wo( mi|amw |am KU] `w |am
fmf`wy k`c|w`hhmw ad{ |` k`fm dh`cb dcl wmkadwbm dhh `n |am
kdudki|`w{ a`hlicb d 4 gmn`wm |amy li{kadwbm# \` l` |ai{( |am fmf`wy
k`c|w`hhmw wmdl{ |am fmf`wy dcl |amc rwi|m{ i| wiba| gdko# \ai{ wmnwm{a
`umwd|i`c aduumc{ d}|`fd|ikdhhy |a`}{dcl{ `n |ifm{ umw {mk`cl#
\ai{ wmnwm{a `umwd|i`c i{ ramwm lycdfik WDF bm|{ i|{ cdfm#
Lycdfik WDF ad{ |` gm lycdfikdhhy wmnwm{aml dhh `n |am |ifm `w i|
15
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 81/95
n`wbm|{ rad| i| i{ a`hlicb# \am l`rc{ilm `n dhh `n |ai{ wmnwm{aicb i{ |ad|
i| |dom{ |ifm dcl {h`r{ l`rc |am fmf`wy#
Fmf`wy kmhh{ dwm m|kaml `c|` d {ihik`c rdnmw ic dc dwwdy `n
k`h}fc{ !gi| hicm{) dcl w`r{ !r`wl hicm{)# \am ic|mw{mk|i`c `n d gi| hicm
dcl r`wl hicm k`c{|i|}|m{ |am dllwm{{ `n |am fmf`wy kmhh#
LWDF r`wo{ gy {mclicb d kadwbm |aw`}ba |am duuw`uwid|m
k`h}fc !KD[) |` dk|i~d|m |am |wdc{i{|`w d| mdka gi| ic |am k`h}fc#
Ramc rwi|icb( |am w`r hicm{ k`c|dic |am {|d|m |am kdudki|`w {a`}hl |dom
`c# Ramc wmdlicb |am {mc{m&dfuhinimw lm|mwficm{ |am hm~mh `n kadwbm ic
|am kdudki|`w#
In i| i{ f`wm |adc =5 umwkmc|( i| wmdl{ i| d{ d 4? `|amwri{m i|
wmdl{ i| d{ d 5# \am k`}c|mw |wdko{ |am wmnwm{a {mt}mckm gd{ml `c
raika w`r{ ad~m gmmc dkkm{{ml ic rad| `wlmw# \am hmcb|a `n |ifm
cmkm{{dwy |` l` dhh |ai{ i{ {` {a`w| |ad| i| i{ mquwm{{ml ic cdc`{mk`cl{
!gihhi`c|a{ `n d {mk`cl)# D fmf`wy kaiu wd|icb `n 25c{ fmdc{ |ad| i|
|dom{ 25 cdc`{mk`cl{ |` k`fuhm|mhy wmdl dcl wmkadwbm mdka kmhh#
Fmf`wy kmhh{ dh`cm r`}hl gm r`w|ahm{{ ri|a`}| {`fm rdy |` bm|
icn`wfd|i`c ic dcl `}| `n |amf# [` |am fmf`wy kmhh{ ad~m d ra`hm
{}uu`w| icnwd{|w}k|}wm `n `|amw {umkidhizml kiwk}i|{# \am{m kiwk}i|{
umwn`wf n}ck|i`c{ {}ka d{:
‧ Ilmc|inyicb mdka w`r dcl k`h}fc !w`r dllwm{{ {mhmk| dcl
k`h}fc dllwm{{ {mhmk|)
14
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 82/95
‧ Ommuicb |wdko `n |am wmnwm{a {mt}mckm !k`}c|mw)
‧ Wmdlicb dcl wm{|`wicb |am {ibcdh nw`f d kmhh !{mc{m dfuhinimw)
‧ \mhhicb d kmhh ram|amw i| {a`}hl |dom d kadwbm `w c`| !rwi|m
mcdghm)
@|amw n}ck|i`c{ `n |am fmf`wy k`c|w`hhmw ickh}lm d {mwim{ `n
|d{o{ |ad| ickh}lm ilmc|inyicb |am |yum( {umml dcl df`}c| `n fmf`wy
dcl kamkoicb n`w mww`w{#
[|d|ik WDF }{m{ d k`fuhm|mhy linnmwmc| |mkac`h`by# Ic {|d|ik
WDF( d n`wf `n nhiu&nh`u a`hl{ mdka gi| `n fmf`wy# D nhiu&nh`u n`w d
fmf`wy kmhh |dom{ n`}w `w {iq |wdc{i{|`w{ dh`cb ri|a {`fm riwicb( g}|
cm~mw ad{ |` gm wmnwm{aml#
\ai{ fdom{ {|d|ik WDF {ibcinikdc|hy nd{|mw |adc lycdfik WDF#
A`rm~mw( gmkd}{m i| ad{ f`wm udw|{( d {|d|ik fmf`wy kmhh |dom{ }u d
h`| f`wm {udkm `c d kaiu |adc d lycdfik fmf`wy kmhh# \amwmn`wm( y`}
bm| hm{{ fmf`wy umw kaiu( dcl |ad| fdom{ {|d|ik WDF d h`| f`wm
mqumc{i~m#
[|d|ik WDF i{ nd{| dcl mqumc{i~m( dcl lycdfik WDF i{ hm{{
mqumc{i~m dcl {h`rmw# [|d|ik WDF i{ }{ml |` kwmd|m |am KU]"{ {umml&
{mc{i|i~m kdkam# Lycdfik WDF n wf{ |am hdwbmw {y{|mf WDF {udkm#
Fmf`wy kaiu{ ic lm{o|`u k`fu}|mw{ `wibicdhhy }{ml d uic
k`cnib}wd|i`c kdhhml l}dh ichicm udkodbm !LIU)# \ai{ uic k`cnib}wd|i`c
17
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 83/95
k`}hl gm {`hlmwml ic|` a`hm{ `c |am k`fu}|mw"{ f`|amwg`dwl `w
uh}bbml ic|` d {`kom| |ad| rd{ {`hlmwml `c |am f`|amwg`dwl# \ai{
fm|a`l r`woml nicm ramc k`fu}|mw{ |yuikdhhy `umwd|ml `c d k`}uhm `n
fmbdgy|m{ `w hm{{ `n WDF( g}| d{ |am cmml n`w fmf`wy bwmr( |am
c}fgmw `n kaiu{ cmmlicb {udkm `c |am f`|amwg`dwl ickwmd{ml#
\am {`h}|i`c rd{ |` uhdkm |am fmf`wy kaiu{( dh`cb ri|a dhh `n |am
{}uu`w| k`fu`cmc|{( `c d {mudwd|m uwic|ml kiwk}i| g`dwl !UKG) |ad|
k`}hl |amc gm uh}bbml ic|` d {umkidh k`ccmk|`w !fmf`wy gdco) `c |am
f`|amwg`dwl# F`{| `n |am{m kaiu{ }{m d {fdhh `}|hicm J&hmdl ![@J) uic
k`cnib}wd|i`c( g}| t}i|m d nmr fdc}ndk|}wmw{ }{m |am |aic {fdhh `}|hicm
udkodbm !\[@U) k`cnib}wd|i`c d{ rmhh#
\am omy linnmwmckm gm|rmmc |am{m cmrmw uic |yum{ dcl |am
`wibicdh LIU k`cnib}wd|i`c i{ |ad| [@J dcl \[@U kaiu{ dwm {}wndkm&
f`}c|ml |` |am UKG# Ic `|amw r`wl{( |am uic{ dwm {`hlmwml liwmk|hy |`
|am {}wndkm `n |am g`dwl( c`| ic{mw|ml ic a`hm{ `w {`kom|{#
Fmf`wy kaiu{ dwm c`wfdhhy `chy d~dihdghm d{ udw| `n d kdwl kdhhml
d f`l}hm# Y`}"~m uw`gdghy {mmc fmf`wy hi{|ml d{ 1q;7 `w <q4># \am{m
c}fgmw{ wmuwm{mc| |am c}fgmw `n |am kaiu{ f}h|iuhiml gy |am kdudki|y
`n mdka icli~il}dh kaiu( raika i{ fmd{}wml ic fmbdgi|{ !Fg)( `w `cm
fihhi`c gi|{#
\dom |am wm{}h| dcl li~ilm i| gy miba| |` bm| |am c}fgmw `n
fmbdgy|m{ `c |ad| f`l}hm# N`w mqdfuhm( <q;7 fmdc{ |ad| |am f`l}hm
ad{ n`}w ;7&fmbdgi| kaiu{# F}h|iuhy < gy ;7 dcl y`} bm| 471 fmbdgi|{#
1;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 84/95
[ickm rm oc`r |ad| d gy|m ad{ 1 gi|{( rm cmml |` li~ilm `}w wm{}h| `n
471 gy 1# @}w wm{}h| i{ 4> fmbdgy|m{$
I|"{ gmmc {dil |ad| y`} kdc cm~mw ad~m mc`}ba f`cmy# \am
{dfm a`hl{ |w}m n`w WDF( m{umkidhhy in y`} l` d h`| `n bwduaik{&
ic|mc{i~m r`wo `w bdficb# Cmq| |` |am KU] i|{mhn( WDF i{ |am f`{|
ifu`w|dc| ndk|`w ic k`fu}|mw umwn`wfdckm# In y`} l`c"| ad~m mc`}ba(
dllicb WDF kdc fdom f`wm `n d linnmwmckm |adc bm||icb d cmr KU]$
In y`}w {y{|mf wm{u`cl{ {h`rhy `w dkkm{{m{ |am adwl lwi~m
k`c{|dc|hy( |amc y`} cmml |` dll f`wm WDF# In y`} dwm w}ccicb
Ricl`r{ QU( Fikw`{`n| wmk`ffmcl{ 471FG d{ |am ficif}f WDF
wmt}iwmfmc|# D| ><FG( y`} fdy mqumwimckm nwmt}mc| duuhikd|i`c
uw`ghmf{#
N`w `u|ifdh umwn`wfdckm ri|a {|dcldwl lm{o|`u duuhikd|i`c{(
7=>FG i{ wmk`ffmclml# In y`} dwm w}ccicb Ricl`r{ 9=/91( y`} cmml
d gdwm ficif}f `n ;7 FG( dcl y`}w k`fu}|mw rihh r`wo f}ka gm||mw
ri|a >< FG# Ricl`r{ C\/7555 cmml{ d| hmd{| >< FG( dcl i| rihh |dom
m~mwy|aicb y`} kdc |aw`r d| i|( {` y`}"hh uw`gdghy rdc| 471 FG `w
f`wm#
Hic}q r`wo{ aduuihy `c d {y{|mf ri|a `chy < FG `n WDF# In y`}
uhdc |` dll Q&Ricl`r{ `w l` f}ka {mwi`}{ r`wo( a`rm~mw( y`}"hh
uw`gdghy rdc| >< FG# Fdk @[ Q {y{|mf{ {a`}hl ad~m d ficif}f `n
471 FG( `w n`w `u|ifdh umwn`wfdckm( =47 FG#
\am df`}c| `n WDF hi{|ml n`w mdka {y{|mf dg`~m i{ m{|ifd|ml n`w
c`wfdh }{dbm && dkkm{{icb |am Ic|mwcm|( r`wl uw`km{{icb( {|dcldwl
1<
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 85/95
a`fm/`nnikm duuhikd|i`c{ dcl hiba| mc|mw|dicfmc|# In y`} l` k`fu}|mw&
dilml lm{ibc !KDL)( ;&L f`lmhicb/dcifd|i`c `w amd~y ld|d
uw`km{{icb( `w in y`} dwm d {mwi`}{ bdfmw( |amc y`} rihh uw`gdghy cmml
f`wm WDF# Y`} fdy dh{` cmml f`wm WDF in y`}w k`fu}|mw dk|{ d{ d
{mw~mw `n {`fm {`w| !Rmg udbm{( ld|dgd{m( duuhikd|i`c( N\U `w
cm|r`wo)#
Dc`|amw t}m{|i`c i{ a`r f}ka ^WDF y`} rdc| `c y`}w ~ilm`
kdwl# Dhf`{| dhh kdwl{ |ad| y`} kdc g}y |`ldy ad~m d| hmd{| 4> FG `n
WDF# \ai{ i{ c`wfdhhy mc`}ba |` `umwd|m ic d |yuikdh `nnikm
mc~iw`cfmc|# Y`} {a`}hl uw`gdghy ic~m{| ic d ;7&FG `w gm||mw bwduaik{
kdwl in y`} rdc| |` l` dcy `n |am n`hh`ricb:
‧Uhdy wmdhi{|ik bdfm{
‧Kdu|}wm dcl mli| ~ilm`
‧Kwmd|m ;&L bwduaik{
‧R`wo ic d aiba&wm{`h}|i`c( n}hh&k`h`w mc~iw`cfmc|
‧Lm{ibc n}hh&k`h`w ihh}{|wd|i`c{
Ramc {a`uuicb n`w ~ilm` kdwl{( wmfmfgmw |ad| y`}w f`ci|`w dcl
k`fu}|mw f}{| gm kdudghm `n {}uu`w|icb |am kdwl y`} ka``{m#
1=
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 86/95
K`fu}|mw Fmf`wy
Y`} dhwmdly oc`r |ad| |am k`fu}|mw ic nw`c| `n y`} ad{ fmf`wy#
Rad| y`} fdy c`| oc`r i{ |ad| f`{| `n |am mhmk|w`cik i|mf{ y`} }{mm~mwy ldy ad~m {`fm n`wf `n fmf`wy dh{`# Amwm dwm j}{| d nmr
mqdfuhm{ `n |am fdcy i|mf{ |ad| }{m fmf`wy:
‧Kmhh ua`cm{
‧ULD{
‧Bdfm k`c{`hm{
‧
Kdw wdli`{ ‧^KW{
‧\^{
Mdka `n |am{m lm~ikm{ }{m{ linnmwmc| |yum{ `n fmf`wy ic linnmwmc|
rdy{$
Dh|a`}ba fmf`wy i{ |mkacikdhhy dcy n`wf `n mhmk|w`cik {|`wdbm( i|
i{ }{ml f`{| `n|mc |` ilmc|iny nd{|( |mfu`wdwy n`wf{ `n {|`wdbm# In y`}w
k`fu}|mw"{ KU] adl |` k`c{|dc|hy dkkm{{ |am adwl lwi~m |` wm|wim~m
m~mwy uimkm `n ld|d i| cmml{( i| r`}hl `umwd|m ~mwy {h`rhy# Ramc |am
icn`wfd|i`c i{ omu| ic fmf`wy( |am KU] kdc dkkm{{ i| f}ka f`wm
t}ikohy# F`{| n`wf{ `n fmf`wy dwm ic|mclml |` {|`wm ld|d |mfu`wdwihy#
\am KU] dkkm{{m{ fmf`wy dkk`wlicb |` d li{|ick| aimwdwkay#
Ram|amw i| k`fm{ nw`f umwfdcmc| {|`wdbm !|am adwl lwi~m) `w icu}|
!|am omyg`dwl) f`{| ld|d b`m{ ic wdcl`f dkkm{{ fmf`wy !WDF) niw{|#
\am KU] |amc {|`wm{ uimkm{ `n ld|d i| rihh cmml |` dkkm{{( `n|mc ic d
1>
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 87/95
kdkam( dcl fdic|dic{ kmw|dic {umkidh ic{|w}k|i`c{ ic |am wmbi{|mw#
Dhh `n |am k`fu`cmc|{ ic y`}w k`fu}|mw( {}ka d{ |am KU]( |am
adwl lwi~m dcl |am `umwd|icb {y{|mf( r`wo |`bm|amw d{ d |mdf( dcl
fmf`wy i{ `cm `n |am f`{| m{{mc|idh udw|{ `n |ai{ |mdf# Nw`f |am
f`fmc| y`} |}wc y`}w k`fu}|mw `c }c|ih |am |ifm y`} {a}| i| l`rc(
y`}w KU] i{ k`c{|dc|hy }{icb fmf`wy# Hm|"{ |dom d h``o d| d |yuikdh
{kmcdwi`:
‧ Y`} |}wc |am k`fu}|mw `c#
‧ \am k`fu}|mw h`dl{ ld|d nw`f wmdl&`chy fmf`wy !W@F) dcl
umwn`wf{ d u`rmw&`c {mhn&|m{| !U@[\) |` fdom {}wm dhh |am fdj`w
k`fu`cmc|{ dwm n}ck|i`cicb uw`umwhy# D{ udw| `n |ai{ |m{|( |am
fmf`wy k`c|w`hhmw kamko{ dhh `n |am fmf`wy dllwm{{m{ ri|a d t}iko
wmdl/rwi|m `umwd|i`c |` mc{}wm |ad| |amwm dwm c` mww`w{ ic |am
fmf`wy kaiu{# Wmdl/rwi|m fmdc{ |ad| ld|d i{ rwi||mc |` d gi| dcl
|amc wmdl nw`f |ad| gi|#
‧ \am k`fu}|mw h`dl{ |am gd{ik icu}|/`}|u}| {y{|mf !GI@[)
nw`f W@F# \am GI@[ uw`~ilm{ |am f`{| gd{ik icn`wfd|i`c dg`}|
{|`wdbm lm~ikm{( g``| {mt}mckm( {mk}wi|y( Uh}b dcl Uhdy !d}|` lm~ikm
wmk`bci|i`c) kdudgihi|y dcl d nmr `|amw i|mf{#
‧ \am k`fu}|mw h`dl{ |am `umwd|icb {y{|mf !@[) nw`f |am adwl
lwi~m ic|` |am {y{|mf"{ WDF# Bmcmwdhhy( |am kwi|ikdh udw|{ `n |am
`umwd|icb {y{|mf dwm fdic|dicml ic WDF d{ h`cb d{ |am k`fu}|mw i{
`c# \ai{ dhh`r{ |am KU] |` ad~m iffmlid|m dkkm{{ |` |am `umwd|icb
{y{|mf( raika mcadckm{ |am umwn`wfdckm dcl n}ck|i`cdhi|y `n |am
12
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 88/95
`~mwdhh {y{|mf#
‧ Ramc y`} `umc dc duuhikd|i`c( i| i{ h`dlml ic|` WDF# \`
k`c{mw~m WDF }{dbm( fdcy duuhikd|i`c{ h`dl `chy |am m{{mc|idh
udw|{ `n |am uw`bwdf ici|idhhy dcl |amc h`dl `|amw uimkm{ d{ cmmlml#
‧ Dn|mw dc duuhikd|i`c i{ h`dlml( dcy nihm{ |ad| dwm `umcml n`w
}{m ic |ad| duuhikd|i`c dwm h`dlml ic|` WDF#
‧ Ramc y`} {d~m d nihm dcl kh`{m |am duuhikd|i`c( |am nihm i{
rwi||mc |` |am {umkiniml {|`wdbm lm~ikm( dcl |amc i| dcl |am
duuhikd|i`c dwm u}wbml nw`f WDF#
Ic |am hi{| dg`~m( m~mwy |ifm {`fm|aicb i{ h`dlml `w `umcml( i| i{
uhdkml ic|` WDF# \ai{ {ifuhy fmdc{ |ad| i| ad{ gmmc u}| ic |am
k`fu}|mw"{ |mfu`wdwy {|`wdbm dwmd {` |ad| |am KU] kdc dkkm{{ |ad|
icn`wfd|i`c f`wm md{ihy#
\am KU] wmt}m{|{ |am ld|d i| cmml{ nw`f WDF( uw`km{{m{ i| dcl
rwi|m{ cmr ld|d gdko |` WDF ic d k`c|ic}`}{ kykhm# Ic f`{|
k`fu}|mw{( |ai{ {a}nnhicb `n ld|d gm|rmmc |am KU] dcl WDF aduumc{
fihhi`c{ `n |ifm{ m~mwy {mk`cl#
Ramc dc duuhikd|i`c i{ kh`{ml( i| dcl dcy dkk`fudcyicb nihm{ dwm
}{}dhhy u}wbml !lmhm|ml) nw`f WDF |` fdom w``f n`w cmr ld|d# In |am
kadcbml nihm{ dwm c`| {d~ml |` d umwfdcmc| {|`wdbm lm~ikm gmn`wm
gmicb u}wbml( |amy dwm h`{|#
11
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 89/95
Nd{|( u`rmwn}h KU]{ cmml t}iko dcl md{y dkkm{{ |` hdwbm
df`}c|{ `n ld|d ic `wlmw |` fdqifizm |amiw umwn`wfdckm# In |am KU]
kdcc`| bm| |` |am ld|d i| cmml{( i| hi|mwdhhy {|`u{ dcl rdi|{ n`w i|#
F`lmwc KU]{ w}ccicb d| {umml{ `n dg`}| 4 bibdamw|z kdc
k`c{}fm fd{{i~m df`}c|{ `n ld|d && u`|mc|idhhy gihhi`c{ `n gy|m{ umw
{mk`cl# \am uw`ghmf |ad| k`fu}|mw lm{ibcmw{ ndkm i{ |ad| fmf`wy
|ad| kdc ommu }u ri|a d 4&bibdamw|z KU] i{ mq|wmfmhy mqumc{i~m &&
f}ka f`wm mqumc{i~m |adc dcy`cm kdc dnn`wl ic hdwbm t}dc|i|im{#
K`fu}|mw lm{ibcmw{ ad~m {`h~ml |am k`{| uw`ghmf gy '|imwicb'
fmf`wy && }{icb mqumc{i~m fmf`wy ic {fdhh t}dc|i|im{ dcl |amc
gdkoicb i| }u ri|a hdwbmw t}dc|i|im{ `n hm{{ mqumc{i~m fmf`wy#
\am kamdum{| n`wf `n wmdl/rwi|m fmf`wy ic rilm }{m |`ldy i{
|am adwl li{o# Adwl li{o{ uw`~ilm hdwbm t}dc|i|im{ `n icmqumc{i~m(
umwfdcmc| {|`wdbm# Y`} kdc g}y adwl li{o {udkm n`w umccim{ umw
fmbdgy|m( g}| i| kdc |dom d b``l gi| `n |ifm !duuw`dkaicb d {mk`cl) |`
wmdl d fmbdgy|m `nn d adwl li{o# Gmkd}{m {|`wdbm {udkm `c d adwl li{o
i{ {` kamdu dcl uhmc|in}h( i| n`wf{ |am nicdh {|dbm `n d KU]{ fmf`wy
aimwdwkay( kdhhml ~iw|}dh fmf`wy#
\am cmq| hm~mh `n |am aimwdwkay i{ WDF# \am gi| {izm n d KU]
|mhh{ y`} a`r fdcy gy|m{ `n icn`wfd|i`c i| kdc dkkm{{ nw`f WDF d| |am{dfm |ifm# N`w mqdfuhm( d 4>&gi| KU] kdc uw`km{{ 7 gy|m{ d| d |ifm !4
gy|m 6 1 gi|{( {` 4> gi|{ 6 7 gy|m{)( dcl d ><&gi| KU] kdc uw`km{{ 1
gy|m{ d| d |ifm#
19
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 90/95
Fmbdamw|z !FAz) i{ d fmd{}wm `n d KU]"{ uw`km{{icb {umml( `w
kh`ko kykhm( ic fihhi`c{ umw {mk`cl# [`( d ;7&gi| 155&FAz Umc|i}f III
kdc u`|mc|idhhy uw`km{{ < gy|m{ {if}h|dcm`}{hy( 155 fihhi`c |ifm{ umw
{mk`cl !u`{{ighy f`wm gd{ml `c uiumhicicb)$ \am b`dh `n |am fmf`wy
{y{|mf i{ |` fmm| |a`{m wmt}iwmfmc|{#
D k`fu}|mw"{ {y{|mf WDF dh`cm i{ c`| nd{| mc`}ba |` fd|ka |am
{umml `n |am KU]# \ad| i{ ray y`} cmml d kdkam !li{k}{{ml hd|mw)#
A`rm~mw( |am nd{|mw WDF i{ |am gm||mw# F`{| kaiu{ |`ldy `umwd|m ri|a d
kykhm wd|m `n =5 |` 25 cdc`{mk`cl{# \am wmdl/rwi|m {umml i{ |yuikdhhy d
n}ck|i`c `n |am |yum `n WDF }{ml( {}ka d{ LWDF( [LWDF( WDFG][#
[y{|mf WDF {umml i{ k`c|w`hhml gy g}{ ril|a dcl g}{ {umml#
G}{ ril|a wmnmw{ |` |am c}fgmw `n gi|{ |ad| kdc gm {mc| |` |am KU]
{if}h|dcm`}{hy( dcl g}{ {umml wmnmw{ |` |am c}fgmw `n |ifm{ d bw`}u
`n gi|{ kdc gm {mc| mdka {mk`cl# D g}{ kykhm `kk}w{ m~mwy |ifm ld|d
|wd~mh{ nw`f fmf`wy |` |am KU]#
N`w mqdfuhm( d 455&FAz ;7&gi| g}{ i{ |am`wm|ikdhhy kdudghm `n
{mclicb < gy|m{ !;7 gi|{ li~ilml gy 1 6 < gy|m{) `n ld|d |` |am KU]
455 fihhi`c |ifm{ umw {mk`cl( raihm d >>&FAz 4>&gi| g}{ kdc {mcl 7
gy|m{ `n ld|d >> fihhi`c |ifm{ umw {mk`cl# In y`} l` |am fd|a( y`}"hh
nicl |ad| {ifuhy kadcbicb |am g}{ ril|a nw`f 4> gi|{ |` ;7 gi|{ dcl |am
{umml nw`f >> FAz |` 455 FAz ic `}w mqdfuhm dhh`r{ n`w |awmm |ifm{
d{ f}ka ld|d !<55 fihhi`c gy|m{ ~mw{}{ 4;7 fihhi`c gy|m{) ud{{icb
|aw`}ba |` |am KU] m~mwy {mk`cl#
95
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 91/95
Ic wmdhi|y( WDF l`m{c"| }{}dhhy `umwd|m d| `u|if}f {umml#
Hd|mcky kadcbm{ |am mt}d|i`c wdlikdhhy# Hd|mcky wmnmw{ |` |am c}fgmw
`n kh`ko kykhm{ cmmlml |` wmdl d gi| `n icn`wfd|i`c# N`w mqdfuhm( WDF
wd|ml d| 455 FAz i{ kdudghm `n {mclicb d gi| ic 5#55555554 {mk`cl{(
g}| fdy |dom 5#5555555= {mk`cl{ |` {|dw| |am wmdl uw`km{{ n`w |am
niw{| gi|# \` k`fumc{d|m n`w hd|mcky( KU]{ }{m{ d {umkidh |mkacit}m
kdhhml g}w{| f`lm#
G}w{| f`lm lmumcl{ `c |am mqumk|d|i`c |ad| ld|d wmt}m{|ml gy
|am KU] rihh gm {|`wml ic {mt}mc|idh fmf`wy kmhh{# \am fmf`wy
k`c|w`hhmw dc|ikiud|m{ |ad| rad|m~mw |am KU] i{ r`woicb `c rihh k`c|ic}m
|` k`fm nw`f |ai{ {dfm {mwim{ `n fmf`wy dllwm{{m{( {` i| wmdl{
{m~mwdh k`c{mk}|i~m gi|{ `n ld|d |`bm|amw#
\ai{ fmdc{ |ad| `chy |am niw{| gi| i{ {}gjmk| |` |am n}hh mnnmk| `n
hd|mcky? wmdlicb {}kkm{{i~m gi|{ |dom{ {ibcinikdc|hy hm{{ |ifm# \am wd|ml
g}w{| f`lm `n fmf`wy i{ c`wfdhhy mquwm{{ml d{ n`}w c}fgmw{
{mudwd|ml gy ld{am{#
\am niw{| c}fgmw |mhh{ y`} |am c}fgmw `n kh`ko kykhm{ cmmlml |`
gmbic d wmdl `umwd|i`c? |am {mk`cl( |aiwl dcl n`}w|a c}fgmw{ |mhh y`}
a`r fdcy kykhm{ dwm cmmlml |` wmdl mdka k`c{mk}|i~m gi| ic |am w`r(
dh{` oc`rc d{ |am r`wl hicm# N`w mqdfuhm: =&4&4&4 |mhh{ y`} |ad| i|
|dom{ ni~m kykhm{ |` wmdl |am niw{| gi| dcl `cm kykhm n`w mdka gi| dn|mw
|ad|# @g~i`}{hy( |am h`rmw |am{m c}fgmw{ dwm( |am gm||mw |am
umwn`wfdckm `n |am fmf`wy#
94
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 92/95
G}w{| f`lm i{ `n|mc }{ml ic k`cj}ck|i`c ri|a uiumhicicb( dc`|amw
fmdc{ `n ficifizicb |am mnnmk|{ `n hd|mcky# Uiumhicicb `wbdcizm{ ld|d
wm|wim~dh ic|` d {`w| `n d{{mfghy&hicm uw`km{{# \am fmf`wy k`c|w`hhmw
{if}h|dcm`}{hy wmdl{ `cm `w f`wm r`wl{ nw`f fmf`wy( {mcl{ |am
k}wwmc| r`wl `w r`wl{ |` |am KU] dcl rwi|m{ `cm `w f`wm r`wl{ |`
fmf`wy kmhh{# ]{ml |`bm|amw( g}w{| f`lm dcl uiumhicicb kdc
lwdfd|ikdhhy wml}km |am hdb kd}{ml gy hd|mcky#
[` ray r`}hlc"| y`} g}y |am nd{|m{|( rilm{| fmf`wy y`} kdc
bm|0 \am {umml dcl ril|a `n |am fmf`wy"{ g}{ {a`}hl fd|ka |am
{y{|mf"{ g}{# Y`} kdc }{m fmf`wy lm{ibcml |` r`wo d| 455 FAz ic d
>>&FAz {y{|mf( g}| i| rihh w}c d| |am >>&FAz {umml `n |am g}{ {` |amwm
i{ c` dl~dc|dbm( dcl ;7&gi| fmf`wy r`c"| ni| `c d 4>&gi| g}{#
M~mc ri|a d rilm dcl nd{| g}{( i| {|ihh |dom{ h`cbmw n`w ld|d |` bm|
nw`f |am fmf`wy kdwl |` |am KU] |adc i| |dom{ n`w |am KU] |` dk|}dhhy
uw`km{{ |am ld|d# \ad|"{ ramwm kdkam{ k`fm ic#
K@CKH][I@C
K`fu}|mw `umwd|icb {y{|mf{ dwm |am gd{ik g}ihlicb gh`ko{ n`w
k`fu}|mw }{mw{# I| i{ |am ‘gwdic‖ |ad| dhh`r{ |am k`fu}|mw |` `umwd|m
dcl kdc gm t}i|m ifu`w|dc|#
97
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 93/95
D{ rm ad~m {a`rc y`}( |amwm dwm fdcy |yum{ `n `umwd|icb
{y{|mf{( dcl raika `cm y`} ka``{m i{ d umw{`cdh lmki{i`c# Mdka @[
ad{ i|{ `rc {umkinik dl~dc|dbm{ dcl li{dl~dc|dbm{#
Rad| y`} cmml |` l` i{ h``o d| |am nmd|}wm{ mdka ad{ |` `nnmw dcl
|amc uiko |am `cm |ad| gm{| {}i|{ y`}w cmml{# Y`} l`c’| ad~m |` gm
{|}ko ri|a Ricl`r{ dcy f`wm in y`} l`c’| rdc| |` gm# C`r y`} ad~m d
ka`ikm$
Ramc y`} ad~m d gm||mw }clmw{|dclicb `n rad| `umwd|icb
{y{|mf{ kdc `nnmw( y`}’hh gm gm||mw icn`wfml |` fdom y`}w ka`ikm#
Raihm |am |mwfic`h`by kdc gm k`fuhikd|ml( rm a`um |ad| y`} c`r
}clmw{|dcl |ad| mdka {y{|mf i{ wmdhhy g}ih| ri|a |am }{mw ic ficl raika
i{ |am f`{| ifu`w|dc| k`fu`cmc| |` `umwd|icb {y{|mf lm{ibcmw{#
[` cmq| |ifm y`} h`b `c |` y`}w k`fu}|mw( wmfmfgmw |ad|
gmaicl |am {kmcm{ |amwm dwm fdcy( fdcy |aicb{ b`icb `c |ad| y`}kdc’| {mm# \wy |` ifdbicm y`}w k`fu}|mw }{dbm ri|a`}| |am{m |aicb{#
I| i{ |w}hy fdbikdh |` gm hi~icb ic |am k`fu}|mw dbm# Y`}w `umwd|icb
{y{|mf j}{| fdom{ i| md{imw dcl f`wm mcj`ydghm#
\amwm’{ c` gib {mkwm| |` dc `umwd|icb {y{|mf( g}| c`r( a`umn}hhy(
y`} oc`r f`wm |adc y`} lil gmn`wm ‛ c`r |ad| `umwd|icb {y{|mf{
ad~m gmmc }ck`~mwml$
9;
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 94/95
\am n`hh`ricb rmg{i|m{ rmwm wmnmwmckml ic wm{mdwkaicb |ai{ g``o:
rrr#fikw`{`n|#k`f
rrr#rioiumlid#`wb
rrr#a`r{|}nnr`wo{#k`f
rrr#rmg`umlid#k`f
9<
8/3/2019 Understanding Computer Operating Systems
http://slidepdf.com/reader/full/understanding-computer-operating-systems 95/95
\` U}wkad{m Uwi~d|m Hdgmh Wiba|{ |`
\ai{ Wmu`w|( Uhmd{m Khiko Amwm
\` Bm| F`wm Uwi~d|m Hdgmh K`c|mc| ( Uhmd{m
^i{i| `}w UHW [|`wm