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Chapter 1: Introducing
Operating Systems
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What Is an OperatingSystem?
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A computer system consists of software (programs andhardware
(the physical machine and its electronic components!
"he operating system software is the chief piece of software#the
portion of the computing system that manages all of thehardware and
all of the other software!
"o $e speci%c# it controls e&ery %le# e&ery de&ice#
e&ery sectionof main memory# and e&ery nanosecond of
processing time!
It controls who can use the system and how!
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Operating SystemSoftware
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"he pyramid shown in igure 1!1 is an a$stract representation of
anoperating system and demonstrates how its ma)or components
wor*together!
At the $ase of the pyramid are the four essential managers of
e&eryoperating system: the Memory Manager, theProcessor
Manager#the Device Manager, and the File Manager.
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A network was not always an integral part of operating
systems+early systems were self,contained with all networ*
capa$ilityadded on top of e-isting operating systems! .ow most
operatingsystems routinely incorporate a Network Manager.
/egardless of the si0e or con%guration of the system# each of
the
su$system managers must perform the following tas*s:
onitor its resources continuously 3nforce the policies that
determine who gets what# when# and howmuch Allocate the resource
when appropriate
4eallocate the resource when appropriateApplied Operating System
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"he emory anager (the su$)ect of Chapters 26' is incharge of
main memory# also *nown as /A# short for /andomAccess emory! "he
emory anager chec*s the &alidity of
each re7uest for memory space and# if it is a legal re7uest#
itallocates a portion of memory that isn8t already in use! In
amultiuser en&ironment# the emory anager sets up a ta$leto *eep
trac* of who is using which section of memory! inally#when the time
comes to reclaim the memory# the emory
anager deallocates memory!
A primary responsi$ility of the emory anager is to protectthe
space in main memory occupied $y the operating systemitself9it
can8t allow any part of it to $e accidentally or
intentionally altered!
ain emoryanagement
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"he ;rocessor anager (the su$)ect of Chapters 56ecause it
handles the processes8 transitions from
one state of e-ecution to another# it can $e compared to atrac
controller!
Once the ;rocessor anager allocates the processor# it sets upthe
necessary registers and ta$les and# when the )o$ is %nished
or the ma-imum amount of time has e-pired# it reclaims
theprocessor!
;rocessor anagement
Applied Operating System 0E'B# Jinu-# =.IK
Supercomputers I/IK# Jinu-# =.ICOS
Wor*stations# ser&ers Jinu-# =.IK# Windows
.etwor*s Jinu-# .etWare# =.IK# Windows
;ersonal digitalassistants
>lac*>erry# Jinu-# ;alm OS# Windowso$ile
A brief list of platforms andsample operating systemslisted in
alphabetical
order.
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"ypes of OperatingSystems
1
Operating systems for computers large and small fall into
%&e categoriesdistinguished $y response time and how data is
entered into the system:$atch# interacti&e# real,time# hy$rid#
and em$edded systems!
%atc& systems date from the earliest computers# when they
relied onstac*s of punched cards or reels of magnetic tape for
input! Lo$s wereentered $y assem$ling the cards into a dec* and
running the entire dec* ofcards through a card reader as a group9a
$atch!
'nteractive systemsgi&e a faster turnaround than $atch
systems $ut are
slower thanthe real,time systems we tal* a$out ne-t! "hey were
introduced to satisfythe demandsof users who needed fast turnaround
when de$ugging their programs!
Realtime systems are used in time,critical en&ironments
where relia$ilityis *ey anddata must $e processed within a strict
time limit! "he time limit need not $e
,
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y*rid systems are a com$ination of $atch and
interacti&e!"hey appear to $e interacti&e $ecause
indi&idual users can
access the system and get fast responses# $ut such a
systemactually accepts and runs $atch programs in the
$ac*groundwhen the interacti&e load is light!
+m*edded systems are computers placed inside other
products to add features and capa$ilities! or e-ample# you
%ndem$edded computers in household appliances# automo$iles#digital
music players# ele&ators# and pacema*ers!
Applied Operating System 1rief Distory of OperatingSystem
4e&elopment
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"he e&olution of operating system software parallels the
e&olution of thecomputerhardware it was designed to control!
Dere8s a &ery $rief o&er&iew of thise&olution!
-/s
"he %rst generation of computers (1B561B was a time of
&acuum tu$etechnologyand computers the si0e of classrooms! 3ach
computer was uni7ue instructure and
purpose! "here was little need for standard operating system
software$ecause eachcomputer8s use was restricted to a few
professionals wor*ing onmathematical# scienti%c# or military
applications!
-0/s
Second,generation computers (1B61B
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-1/s
"hird,generation computers date from the mid,1B
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4e&elopment in the 1Bs dramatically impro&ed
thecostEperformance ratio of computer components! Dardwarewas more
Ge-i$le# with logical functions $uilt on easily
replacea$le circuit $oards!
--/s
"he o&erwhelming demand for Internet capa$ility in the
mid,1BBs spar*ed the proliferation of networ*ing capa$ility!
"he
World Wide We$# concei&ed in a paper $y "im
>erners,Jeemade the Internet accessi$le $y computer users
worldwide# not)ust the researchers who had come to depend on it for
glo$alcommunications!
4///s
"he new century emphasi0ed the need for operating systemsto oHer
impro&ed Ge-i$ility# relia$ility# and speed! "o meet theneed
for computers that could accommodate multipleoperating systems
running at the same time and sharingresources# the concept of
&irtual machines was de&eloped and$ecame commercially
&ia$le!
Distory
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5irtuali6ation is the creation of partitions on a single
ser&er# witheach partition supporting a diHerent operating
system! In other
words# it turns a single physical ser&er into multiple
&irtual ser&ers#often with multiple operating systems!
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7&readsulti,core technology helps the operating system
handle threads#
multiple actions thatcan $e e-ecuted at the same time!
#*8ect#riented DesignAn important area of research that resulted
in su$stantial eciencieswas that of the
system architecture of operating systems9the way their
componentsare programmedand organi0ed# speci%cally the use of
o*8ectoriented design and t&ereorgani6ation o"the operating
system8s nucleus# the *ernel!
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9ey 7erms
*atc& system: a type of system de&eloped for the
earliest computers that
used punched cards or tape for input# which were entered in a
$atch!
central processing unit (P!): the component with the circuitry#
theMchips#N tocontrol the interpretation and e-ecution of
instructions!
core: the processing part of a C;= chip made up of the control
unit and the
arithmeticlogic unit (AJ=!
Device Manager: the section of the operating system responsi$le
forcontrolling theuse of de&ices! It monitors e&ery
de&ice# channel# and control unit and chooses
the most ecient way to allocate all of the system8s
de&ices!
em*edded system: a dedicated computer system# often small and
fast# thatresides in alarger physical system such as )et aircraft
or ships!
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main"rame: the historical name gi&en to a large computer
systemcharacteri0ed $y itslarge si0e# high cost# and high
performance!
Memory Manager: the section of the operating system responsi$le
forcontrolling theuse of memory! It chec*s the &alidity of each
re7uest for memory space and# ifit8s alegal re7uest# allocates the
amount needed to e-ecute the )o$!
microcomputer: a small computer e7uipped with all the hardware
andsoftwarenecessary to perform one or more tas*s!
minicomputer: a small to medium,si0ed computer system# also
called amidrangecomputer!
multiprocessing: when two or more C;=s share the same main
memory#most IEOde&ices# and the same control program routines!
"hey ser&ice the same )o$stream ande-ecute distinct processing
programs concurrently!
multiprogramming: a techni7ue that allows a single processor to
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network: a system of interconnected computer systems and
peripheral de&icesthate-change information with one
another!
Network Manager: the section of the operating system responsi$le
forcontrollingaccess to and the use of networ*ed resources!
o*8ectoriented: a programming philosophy where$y programs
consist ofselfcontained#reusa$le modules called o$)ects# each of
which supports a speci%c function#$ut which are categori0ed into
classes of o$)ects that share the same function!
operating system: the software that manages all the resources of
a computersystem!
Processor Manager: a composite of two su$managers# the Lo$
Scheduler andthe;rocess Scheduler# which decides how to allocate
the C;=!
realtime system: a computing system used in time,critical
en&ironments thatre7uireguaranteed response times# such as
na&igation systems# rapid transit systems#
andindustrial control s stems!
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so"tware: a collection of programs used to perform certain
tas*s! Software fallsintothree main categories: operating system
programs# compilers and assem$lers#and
application programs!
storage: a place where data is stored in the computer system!
;rimary storage ismainmemory and secondary storage is
non&olatile media!
supercomputer: the fastest# most sophisticated computers made#
used for
comple-calculations!
t&read: a portion of a program that can run independently of
other portions!ultithreaded application programs can ha&e
se&eral threads running at one timewith
the same or diHerent priorities!
t&roug&put: a composite measure of a system8s eciency
that counts thenum$er of
)o$s ser&ed in a gi&en unit of time!
virtuali6ation: the creation of a &irtual &ersion of
hardware or software!
Operating system&irtuali0ation allows a single C;= to run
multiple operating system images at the
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