Sess

ion #

2026

: J2M

E Plat

form

, Con

nect

ed Li

mite

d Dev

ice C

onfig

urat

ion (C

LDC)

Vir

tual

Mac

hin

e D

esig

nL

ectu

re 1

: O

verv

iew

an

d H

isto

ry

Ant

ero

Tai

vals

aari

Aug

ust 2

003

2

Wel

com

e!

•W

elco

me

to th

e V

irtua

l Mac

hine

Des

ign

Sem

inar

.

•T

UT

sem

inar

810

9035

.

==

==

==

==

==

==

==

==

==

==

==

==

==

==

==

=

•F

irst t

ime

a V

M d

esig

n co

urse

has

bee

n or

gani

zed

in F

inla

nd.

•G

lad

to s

ee th

at th

ere

is s

o m

uch

inte

rest

in th

is to

pic!

3

Go

als

●In

trod

uce

you

to th

e w

orld

of v

irtua

l mac

hine

(V

M)

desi

gn.

●E

xpla

in th

e ke

y te

chno

logi

es th

at a

re

need

ed fo

r bu

ildin

g vi

rtua

l mac

hine

s,

such

as

auto

mat

ic m

emor

y m

anag

emen

t, in

terp

reta

tion,

mul

tithr

eadi

ng, a

nd

dyna

mic

com

pila

tion.

4Str

uct

ure

of

the

Sem

inar

•T

he s

emin

ar c

onsi

sts

of tw

o pa

rts:

–Le

ctur

es (

6 or

7 le

ctur

es in

tota

l)–

Stu

dent

pre

sent

atio

ns

•Le

ctur

es w

ill b

e he

ld in

roo

m T

B22

3 on

W

edne

sday

s, 1

0:15

– 1

1:45

am

.–

Lect

ure

atte

ndan

ce is

not

req

uire

d bu

t rec

omm

ende

d.

•T

o ge

t the

cre

dits

(2

ov),

you

mus

t pre

pare

and

gi

ve a

pre

sent

atio

n on

a s

elec

ted

topi

c re

late

d to

virt

ual m

achi

ne d

esig

n.–

Pre

sent

atio

ns w

ill b

egin

in N

ovem

ber.

–A

list

of s

ugge

sted

topi

cs w

ill b

e av

aila

ble

late

r.

5Lec

ture

Sch

edu

le (

Pre

limin

ary)

•S

ep 1

0: H

isto

ry a

nd o

verv

iew

of V

M d

esig

n

•S

ep 1

7: M

emor

y m

anag

emen

t

•S

ep 2

4: In

terp

reta

tion

and

exec

utio

n

•O

ct 1

: Mul

tithr

eadi

ng, s

ynch

roni

zatio

n an

d I/O

•O

ct 8

: Int

erna

ls o

f the

Jav

a vi

rtua

l mac

hine

(O

ct 1

5: N

o le

ctur

e)

(O

ct 2

2: N

o le

ctur

e)

•O

ct 2

9: H

igh

perf

orm

ance

VM

s (g

uest

lect

ure)

•N

ov 5

: Stu

dent

pre

sent

atio

ns b

egin

6Ab

ou

t th

e L

ectu

rer

•B

uilt

virt

ual m

achi

nes

sinc

e th

e m

id-1

980s

.–

Mai

n in

tere

sts

in th

e 19

80s/

early

199

0s:

For

th, S

mal

ltalk

, Sel

f, ot

her

“dyn

amic

” O

O la

ngua

ges.

•In

199

7, m

oved

to C

alifo

rnia

to w

ork

on J

ava

virt

ual m

achi

nes

at S

un M

icro

syst

ems.

–W

rote

the

K V

irtua

l Mac

hine

(K

VM

) at

Sun

Lab

s in

199

8.–

KV

M b

ecam

e th

e st

artin

g po

int f

or J

ava

2 M

icro

Edi

tion

(J2M

E),

a p

opul

ar v

ersi

on o

f the

Jav

a pl

atfo

rm fo

r m

obile

de

vice

s.

•E

ngin

eerin

g m

anag

er o

f the

J2M

E/K

VM

virt

ual

mac

hine

team

at J

ava

Sof

twar

e, 1

999-

2001

.–

Led

early

J2M

E s

tand

ards

act

iviti

es (

CLD

C 1

.0/1

.1)

–C

o-au

thor

of t

he fi

rst J

ava

Ser

ies

book

on

J2M

E.

7

Intr

od

uct

ion

8Wh

at is

a V

irtu

al M

ach

ine?

•A

virt

ual m

achi

ne (

VM

) is

an

“abs

trac

t”

com

putin

g ar

chite

ctur

e or

com

puta

tiona

l en

gine

that

is in

depe

nden

t of a

ny p

artic

ular

ha

rdw

are

or o

pera

ting

syst

em.

•“S

oftw

are

mac

hine

” th

at r

uns

on to

p of

a r

eal

hard

war

e pl

atfo

rm a

nd o

pera

ting

syst

em.

•A

llow

s th

e sa

me

prog

ram

s to

run

“vi

rtua

lly”

on a

ny h

ardw

are

for

whi

ch a

VM

is a

vaila

ble.

9Ch

arac

teri

stic

s o

f a

Vir

tual

Mac

hin

e

•A

virt

ual m

achi

ne ty

pica

lly in

trod

uces

its

own

inst

ruct

ion

set t

hat i

s us

ed fo

r ex

ecut

ing

prog

ram

s.–

Thi

s in

stru

ctio

n se

t is

inde

pend

ent o

f the

arc

hite

ctur

eof

the

host

ope

ratin

g sy

stem

.

•A

virt

ual m

achi

ne u

sual

ly a

lso

has

its o

wn

mem

ory

syst

em.

–A

cces

s to

the

mem

ory

syst

em o

f the

hos

t ope

ratin

g sy

stem

is m

inim

ized

.

•In

gen

eral

, acc

ess

to th

e ho

st o

pera

ting

syst

em

is o

ften

limite

d an

d co

ntro

lled

by th

e vi

rtua

l m

achi

ne's

nat

ive

func

tion

inte

rfac

e.

10Typ

ical

Hig

h-L

evel

Arc

hit

ectu

re

Har

dwar

e

Ope

ratin

g S

yste

m

Virt

ual M

achi

ne

App

licat

ion

11Exa

mp

le:

Co

mp

on

ents

of

a Ja

va

Vir

tual

Mac

hin

e (J

VM

)

Mem

ory

Sys

tem

and

Gar

bage

Col

lect

or

Nat

ive

Inte

rfac

eIn

tern

al R

untim

eS

truc

ture

s

Thr

eadi

ng S

yste

m a

nd T

hrea

d S

ched

uler

Inte

rpre

ter

and

Exe

cutio

n S

tack

s

Cla

ss L

oade

r an

d JA

R R

eade

r

Com

pile

r(o

ptio

nal)

Ver

ifier

12So

me

Bac

kgro

un

d

•V

irtua

l mac

hine

s ha

ve b

een

stud

ied

and

built

si

nce

the

late

195

0s.

•M

any

early

pro

gram

min

g la

ngua

ges

wer

e bu

ilt

arou

nd th

e id

ea o

f hav

ing

a po

rtab

le r

untim

e sy

stem

.

•Y

et V

M d

esig

n w

as a

lway

s a

fairl

y sp

ecia

lized

to

pic;

not

man

y bo

oks

or a

rtic

les

wer

e w

ritte

n un

til r

ecen

tly.

•P

opul

arity

of t

he a

rea

expl

oded

in th

e m

id-1

990s

whe

n th

e Ja

va p

rogr

amm

ing

lang

uage

was

intr

oduc

ed.

13Lan

gu

ages

th

at U

seV

irtu

al M

ach

ines

•W

ell-k

now

n la

ngua

ges

usin

g a

virt

ual m

achi

ne:

–Li

sp s

yste

ms,

195

8/19

60-1

980s

–B

asic

, 196

4-19

80s

–F

orth

, ear

ly 1

970s

–P

asca

l (P

-Cod

e ve

rsio

ns),

late

197

0s/e

arly

198

0s–

Sm

allta

lk, 1

970s

-198

0s–

Sel

f, la

te 1

980/

early

199

0s–

Java

, mid

-199

0s

•N

umer

ous

othe

r la

ngua

ges:

–...

Pos

tScr

ipt,

TC

L/T

K, P

erl,

Pyt

hon,

C#,

...

14Wh

y ar

e V

irtu

al M

ach

ines

In

tere

stin

g?

•P

rovi

de p

latfo

rm in

depe

nden

ce.

•Is

olat

e pr

ogra

ms

from

har

dwar

e de

tails

.

•S

impl

ify a

pplic

atio

n co

de m

igra

tion.

•C

an s

uppo

rt d

ynam

ic d

ownl

oadi

ng o

f sof

twar

e.

•C

an p

rovi

de a

dditi

onal

sec

urity

that

mac

hine

-sp

ecifi

c im

plem

enta

tions

can

not p

rovi

de.

•C

an h

ide

com

plex

ity o

f leg

acy

syst

ems.

•M

any

prog

ram

min

g la

ngua

ges

are

built

aro

und

a vi

rtua

l mac

hine

.

15Vir

tual

Mac

hin

es v

s. O

per

atin

g

Sys

tem

s•

The

re is

a lo

t of s

imila

rity

betw

een

VM

and

OS

de

sign

.–

The

key

com

pone

nt a

reas

are

pre

tty m

uch

the

sam

e (m

emor

y m

anag

emen

t, m

ultit

hrea

ding

, I/O

, ...)

•A

few

key

diff

eren

ces:

–V

irtua

l mac

hine

s ar

e us

ually

des

igne

d to

be

as

inde

pend

ent o

f the

hos

t ope

ratin

g sy

stem

as

poss

ible

.–

Ope

ratin

g sy

stem

s ar

e “e

xten

sion

s of

the

unde

rlyin

g ha

rdw

are”

. The

y ar

e bu

ilt to

faci

litat

e ac

cess

to th

e un

derly

ing

com

putin

g ar

chite

ctur

e an

d m

axim

ize

the

utili

zatio

n of

the

hard

war

e re

sour

ces.

–A

lso,

virt

ual m

achi

nes

are

com

mon

ly ti

ed to

a p

artic

ular

pr

ogra

mm

ing

lang

uage

or

lang

uage

fam

ily.

–O

pera

ting

syst

ems

are

usua

lly la

ngua

ge-in

depe

nden

t.

16Exi

stin

g M

ater

ial o

n V

M D

esig

n

•T

here

is a

lot o

f mat

eria

l ava

ilabl

e on

virt

ual

mac

hine

s.

•H

owev

er, t

he m

ater

ial i

s sc

atte

red/

frag

men

ted

and

it is

diff

icul

t to

find

any

com

preh

ensi

ve

pres

enta

tions

.

•A

few

boo

ks o

n th

e to

pic:

–B

ill B

lund

en, V

irtua

l Mac

hine

Des

ign

and

Impl

emen

tatio

n in

C/C

++, W

ordw

are

Pub

lishi

ng, M

arch

200

2.–

Ron

ald

Mak

, Writ

ing

Com

pile

rs a

nd In

terp

rete

rs, J

ohn

Wile

y &

Son

s, J

uly

1996

.

•U

nfor

tuna

tely

, the

se b

ooks

don

't co

ver

the

area

ve

ry w

ell.

17

A B

rief

His

tory

of

Pro

gra

mm

ing

Lan

gu

ages

th

atU

tiliz

e a

Vir

tual

Mac

hin

e

18LIS

P

•Jo

hn M

cCar

thy,

195

8–

http

://w

ww

-for

mal

.sta

nfor

d.ed

u/jm

c/hi

stor

y/lis

p/lis

p.ht

ml

–LI

SP

is th

e se

cond

old

est p

rogr

amm

ing

lang

uage

stil

l in

wid

espr

ead

use

(afte

r F

ortr

an)

•LI

SP

is c

hara

cter

ized

by

the

follo

win

g id

eas:

–C

ompu

ting

with

sym

bolic

exp

ress

ions

rat

her

than

nu

mbe

rs,

–re

pres

enta

tion

of s

ymbo

lic e

xpre

ssio

ns a

nd o

ther

in

form

atio

n by

list

str

uctu

re,

–co

mpo

sitio

n of

func

tions

as

a to

ol fo

r fo

rmin

g m

ore

com

plex

func

tions

out

of a

few

prim

itive

ope

ratio

ns,

–th

e re

pres

enta

tion

of L

ISP

pro

gram

s as

LIS

P d

ata,

and

th

e fu

nctio

n ev

al th

at s

erve

s bo

th a

s a

form

al d

efin

ition

of th

e la

ngua

ge a

nd a

s an

inte

rpre

ter.

19Sam

ple

Lis

p C

od

e

(d

efin

e (p

rimes

)

(le

trec

((s

ieve

(la

mbd

a (s

)

(

cons

(ca

r s)

(del

ay (

siev

e (f

ilter

(

lam

bda

(n)

(>

(re

mai

nder

n (

car

s))

0))

(f

orce

(cd

r s)

))))

))))

(s

ieve

(fo

rce

(cdr

nat

))))

)

20Wh

y is

Lis

p In

tere

stin

g f

rom

VM

Des

ign

er's

Vie

wp

oin

t?

•T

he fi

rst l

angu

age

to w

idel

y us

e ga

rbag

e co

llect

ion

as a

m

eans

of a

utom

atin

g m

emor

y m

anag

emen

t.

•T

he fi

rst l

angu

age

to u

se r

ecur

sion

ext

ensi

vely

.

•O

ne o

f the

firs

t tru

ly in

tera

ctiv

e la

ngua

ges

that

did

n't r

equi

re

a “c

ompi

le-li

nk-e

xecu

te-c

rash

-deb

ug”

cycl

e.

•Li

sp w

as o

ne o

f the

firs

t sys

tem

s w

here

pro

gram

s ru

n in

a

“san

dbox

”; a

cces

s to

the

oper

atin

g sy

stem

is li

mite

d an

d pr

ogra

ms

cann

ot r

eally

cra

sh th

e sy

stem

.

•T

he fi

rst t

ruly

“re

flect

ive”

pro

gram

min

g la

ngua

ge a

s w

ell;

LIS

P h

as a

ver

y sm

all l

angu

age

core

; the

res

t of t

he s

yste

m

can

be w

ritte

n in

itse

lf; p

rogr

ams

can

be m

anip

ulat

ed a

s da

ta.

21UC

SD

Pas

cal

•T

he P

asca

l lan

guag

e w

as d

evel

oped

by

Nic

klau

s W

irth

in 1

969.

•A

fairl

y “c

onve

ntio

nal”

prog

ram

min

g la

ngua

ge.

–P

rede

cess

or to

a la

rge

fam

ily o

f oth

er la

ngua

ges

(Mod

ula.

.., O

bero

n...)

•P

asca

l did

not

bec

ome

popu

lar

until

Ken

B

owle

s of

the

Uni

vers

ity o

f Cal

iforn

ia S

an

Die

go (

UC

SD

) im

plem

ente

d th

e P

-Cod

e sy

stem

in th

e la

te 1

970s

.–

A p

orta

ble

pseu

doco

de s

yste

m/la

ngua

ge r

untim

e.–

http

://w

ww

.thre

edee

.com

/jcm

/psy

stem

/–

The

P-C

ode

syst

em m

ade

the

impl

emen

tatio

n ex

trem

ely

port

able

, inc

reas

ing

the

popu

larit

y of

Pas

cal r

apid

ly.

22Sam

ple

Pas

cal C

od

e

PR

OG

RA

M F

ibon

acci

(inpu

t,out

put)

;

V

AR

lo :

INT

EG

ER

; hi :

INT

EG

ER

; n :

INT

EG

ER

;

gold

en_r

atio

: D

OU

BLE

; rat

io :

DO

UB

LE;

B

EG

IN

gold

en_r

atio

:= (

1.0

+ s

qrt(

5.0)

)/2.

0;

lo :=

1; h

i :=

1; n

:= 1

;

WH

ILE

hi >

0 D

O

BE

GIN

n

:= n

+ 1

; rat

io :=

hi /

lo;

W

RIT

ELN

(n :

2, '

', hi

, rat

io :

25, '

', (

ratio

- g

olde

n_ra

tio)

: 21

: 18)

;

hi

:= lo

+ h

i; lo

:= h

i - lo

EN

D

E

ND

23Wh

y is

UC

SD

Pas

cal I

nte

rest

ing

fro

m V

M D

esig

ner

's V

iew

po

int?

•T

he P

-Cod

e sy

stem

pop

ular

ized

the

idea

of

usin

g ps

eudo

code

to im

prov

e po

rtab

ility

of

prog

ram

min

g la

ngua

ge r

untim

e sy

stem

s.

•U

ses

a st

ack-

orie

nted

inst

ruct

ion

set a

nd fi

ve

virt

ual r

egis

ters

.–

Onl

y on

e st

ack

(no

sepa

rate

ope

rand

& c

all s

tack

s)

•T

he fi

rst v

irtua

l mac

hine

impl

emen

tatio

n w

idel

y av

aila

ble

to h

obby

ists

.–

Esp

ecia

lly th

e A

pple

II im

plem

enta

tion

was

ver

y po

pula

r.–

http

://ho

mep

ages

.cw

i.nl/~

stev

en/p

asca

l/boo

k/10

pcod

e.ht

ml

–ht

tp://

ww

w.w

ikip

edia

.org

/wik

i/P-C

ode_

mac

hine

24P-C

od

e S

amp

le In

stru

ctio

ns

In

st.

Sta

ckS

tack

Des

crip

tion

befo

reaf

ter

A

DI

i1 i2

i1+

i2ad

d tw

o in

tege

rs

A

DR

r1 r

2r1

+r2

add

two

real

s

D

VI

i1 i2

i1/i2

inte

ger

divi

sion

IN

Ni1

s1

b1se

t mem

bers

hip;

b1

= w

heth

er i1

is a

mem

ber

of s

1

LD

CI

i1i1

load

inte

ger

cons

tant

M

OV

a1 a

2m

ove

N

OT

b1~

b1bo

olea

n ne

gatio

n

25BA

SIC

•B

egin

ners

All-

purp

ose

Sym

bolic

Inst

ruct

ion

Cod

e.

•D

evel

oped

by

John

Kem

eny

and

Tho

mas

Kur

tz

at D

artm

outh

Col

lege

(U

SA

) in

mid

-196

0s.

–ht

tp://

ww

w.k

basi

c.or

g/1/

hist

ory.

php3

•In

tera

ctiv

e na

ture

mad

e it

suita

ble

for

min

i-an

d m

icro

com

pute

rs (

good

tim

ing!

)

•P

aul A

llen

and

Bill

Gat

es w

rote

the

first

in

terp

rete

d im

plem

enta

tion

in 1

975;

this

im

prov

ed th

e po

rtab

ility

of t

he la

ngua

ge

dram

atic

ally

.

26Sam

ple

BA

SIC

Co

de

10

0 IN

PU

T “

Typ

e a

num

ber”

; N

12

0 IF

N <

= 0

GO

TO

200

13

0 P

RIN

T “

Squ

are

root

=”

SQ

R(N

)

14

0 G

OT

O 1

00

20

0 P

RIN

T “

Num

ber

mus

t be

> 0

”

21

0 G

OT

O 1

00

27Wh

y is

BA

SIC

Inte

rest

ing

fro

m V

M

Des

ign

er's

Vie

wp

oin

t?•

It re

ally

isn'

t ver

y in

tere

stin

g...

–T

he la

ngua

ge h

as n

o sp

ecifi

c co

ntrib

utio

ns e

xcep

t eas

e of

lear

ning

and

eas

e of

use

.–

Exc

essi

ve u

se o

f GO

TO

s le

d to

som

e ho

rrib

le p

rogr

ams.

•H

owev

er, t

he p

opul

arity

of B

AS

IC c

oinc

ided

w

ith th

e m

icro

com

pute

r bo

om.

–M

any

early

mic

roco

mpu

ter

com

pani

es d

ecid

ed to

in

tegr

ate

BA

SIC

in th

eir

prod

ucts

.–

You

cou

ld e

ither

pro

gram

in a

ssem

bly

lang

uage

or

BA

SIC

...

•S

ome

BA

SIC

sys

tem

s us

ed p

retty

inte

rest

ing

inte

rmed

iate

cod

e re

pres

enta

tion

tech

niqu

es.

28Fo

rth

•In

vent

ed b

y C

harle

s M

oore

in th

e ea

rly 1

970s

.–

http

://w

ww

.fort

h.co

m/C

onte

nt/H

isto

ry/H

isto

ry1.

htm

•O

rigin

ally

des

igne

d to

con

trol

rad

iote

lesc

opes

.

•C

hara

cter

istic

s:–

For

th is

a “

wor

d-or

ient

ed”

prog

ram

min

g la

ngua

ge; t

here

is

no

synt

ax o

r gr

amm

ar in

the

trad

ition

al s

ense

.–

All

the

prim

itive

func

tions

/wor

ds a

re a

lso

lang

uage

ke

ywor

ds; o

pen

stac

k us

ed fo

r pa

ram

eter

pas

sing

.–

For

th m

akes

sub

rout

ine

defin

ition

ext

rem

ely

chea

p; th

is

prov

ides

for

exte

nsib

ility

and

hig

h le

vel o

f pro

cedu

ral

abst

ract

ion.

–E

xtre

me

min

imal

ism

: The

ent

ire F

orth

sys

tem

(in

clud

ing

a si

mpl

e m

ultit

aski

ng p

rogr

amm

ing

envi

ronm

ent)

can

fit

in 8

-15

kilo

byte

s.

29Sam

ple

Fo

rth

Co

de

: x

Rev

erse

\ rev

erse

the

horiz

onta

l dire

ctio

n of

the

ball

xS

tep

@ +

/- x

Ste

p ! ;

: y

Rev

erse

\ rev

erse

the

vert

ical

dire

ctio

n of

the

ball

yS

tep

@ +

/- y

Ste

p ! ;

: c

heck

Left

\ che

ck fo

r th

e le

ft ed

ge o

f the

scr

een

x

@ 1

<=

IF x

Rev

erse

TH

EN

;

: che

ckR

ight

\ che

ck fo

r th

e rig

ht e

dge

of th

e sc

reen

x

@ x

Max

>=

IF x

Rev

erse

TH

EN

;

A

SC

II o

CO

NS

TA

NT

"ba

ll"

: s

how

Bal

l\ d

raw

the

ball

on th

e sc

reen

"b

all"

xyP

lot ;

: h

ideB

all

\ hid

e (u

ndra

w)

the

ball

"b

l" x

yPlo

t ;

: try

Bal

l\ t

est t

he b

all d

raw

ing

rout

ines

B

EG

IN

sho

wB

all

c

heck

Left

chec

kRig

ht c

heck

Top

che

ckB

otto

m

hid

eBal

l xyS

tep

A

GA

IN ;

30Wh

y is

Fo

rth

Inte

rest

ing

fro

m t

he

VM

Des

ign

er's

Vie

wp

oin

t?•

One

of t

he e

asie

st v

irtua

l mac

hine

s to

bui

ld.

•T

he V

M c

onsi

sts

of a

sm

all n

umbe

r of

dis

tinct

co

mpo

nent

s (s

tack

s, d

ictio

nary

, int

erpr

eter

, vi

rtua

l reg

iste

rs, p

rimiti

ves)

; no

extr

a “f

at”.

•T

he la

ngua

ge it

self

is s

mal

l, si

mpl

e an

d ef

ficie

nt, a

nd p

rovi

des

an u

nusu

al c

ombi

natio

n of

hig

h-le

vel a

bstr

actio

n an

d ve

ry lo

w le

vel

prog

ram

min

g ca

pabi

litie

s.

•H

igh

leve

l of r

efle

ctio

n (s

igni

fican

t por

tions

of

the

VM

writ

ten

in th

e la

ngua

ge it

self.

)

•Id

eal f

or e

mbe

dded

sys

tem

s (if

the

awkw

ard

synt

ax is

not

exp

osed

to th

e en

d us

er...

)

31Sm

allt

alk

•D

evel

oped

by

Ala

n K

ay's

team

at X

erox

PA

RC

–T

here

are

var

ious

ver

sion

s (S

mal

ltalk

-72,

-76

, -80

).

Sm

allta

lk-8

0 is

the

best

kno

wn.

–ht

tp://

user

s.ip

a.ne

t/~dw

ight

h/sm

allta

lk/b

lueb

ook/

blue

book

_im

p_to

c.ht

ml

•C

hara

cter

istic

s:–

The

firs

t tru

ly in

tera

ctiv

e ob

ject

-orie

nted

pro

gram

min

g la

ngua

ge (

unlik

e S

imul

a w

hich

was

a c

ompi

ler-

base

d sy

stem

.)–

Too

k “e

very

thin

g is

an

obje

ct”

and

“mes

sage

pas

sing

” m

etap

hors

to th

e ex

trem

e.–

Eve

ryth

ing

is a

vaila

ble

for

mod

ifica

tion,

eve

n th

e V

M

itsel

f (ve

ry h

igh

leve

l of r

efle

ctio

n.)

–E

ven

code

is tr

eate

d as

obj

ects

(bl

ocks

).–

The

lang

uage

is v

ery

clos

ely

coup

led

with

a g

raph

ical

in

terf

ace;

sou

rce

code

of a

pro

gram

can

not b

e ea

sily

se

para

ted

from

the

prog

ram

min

g en

viro

nmen

t.

32Sam

ple

Sm

allt

alk

Co

de

| a

Str

ing

vow

els

|

aS

trin

g :=

'Thi

s is

a s

trin

g'.

vo

wel

s :=

aS

trin

g se

lect

: [:a

Cha

ract

er |

aCha

ract

er is

Vow

el].

=

==

==

==

==

==

==

==

==

==

==

==

==

==

==

==

| r

ecta

ngle

s aP

oint

|

re

ctan

gles

:= O

rder

edC

olle

ctio

n

w

ith: (

Rec

tang

le le

ft: 0

rig

ht: 1

0 to

p: 1

00 b

otto

m: 2

00)

w

ith: (

Rec

tang

le le

ft: 1

0 rig

ht: 1

0 to

p: 1

10 b

otto

m: 2

10).

aP

oint

:= P

oint

x: 2

0 y:

20.

co

llisi

ons

:= r

ecta

ngle

s se

lect

: [:a

Rec

t | a

Rec

t con

tain

sPoi

nt: a

Poi

nt].

33Wh

y is

Sm

allt

alk

Inte

rest

ing

Fro

m

the

VM

Des

ign

er's

Vie

wp

oin

t?•

Var

ious

impl

emen

tatio

n ch

alle

nges

:–

Eve

ryth

ing

can

be c

hang

ed o

n th

e fly

.–

No

stat

ic ty

pe s

yste

m.

–E

ven

num

bers

are

obj

ects

that

are

man

ipul

ated

by

mes

sage

pas

sing

(=

arit

hmet

ic o

pera

tions

can

be

slow

.)–

Blo

cks

(hea

p-al

loca

ted

code

obj

ects

/sta

ck fr

ames

) ar

e di

fficu

lt to

impl

emen

t effi

cien

tly.

•E

xtre

mel

y in

tera

ctiv

e/re

flect

ive

=>

fun.

•W

ell-d

esig

ned

and

mat

ure

clas

s lib

rarie

s=

> e

asy

to w

rite

inte

rest

ing

softw

are.

•T

here

are

hig

h-qu

ality

pub

lic d

omai

n S

mal

ltalk

im

plem

enta

tions

ava

ilabl

e.–

http

://w

ww

.squ

eak.

org/

34Sel

f•

Inve

nted

by

Dav

id U

ngar

and

Ran

dall

Sm

ith a

t X

erox

PA

RC

and

Sta

nfor

d U

nive

rsity

in

1986

-198

7.–

The

maj

ority

of t

he a

ctua

l im

plem

enta

tion

wor

k w

as d

one

at S

un L

abs

in th

e 19

90s.

–ht

tp://

ww

w.s

unla

bs.c

om/s

elf

•P

roto

type

-bas

ed fl

avor

/var

iant

of S

mal

ltalk

.–

Too

k th

e “e

very

thin

g is

an

obje

ct”

met

apho

r ev

en fu

rthe

r th

an S

mal

ltalk

.–

No

mor

e cl

asse

s; o

bjec

ts c

an in

herit

(“d

eleg

ate”

) be

havi

or d

irect

ly fr

om e

ach

othe

r.–

Ext

rem

ely

dyna

mic

lang

uage

: eve

n th

e co

ntro

l str

uctu

res

or th

e in

herit

ance

rel

atio

nshi

ps o

f obj

ects

can

be

chan

ged

on th

e fly

.

35Sam

ple

Sel

f C

od

e

ac

c: b

ankA

ccou

nt c

opy.

ac

c ba

lanc

e: 1

00.

b:

[acc

dep

osit:

50]

.

ac

c ba

lanc

e."r

etur

ns 1

00"

b

valu

e.

b

valu

e.

ac

c ba

lanc

e."r

etur

ns 2

00"

36Wh

y is

Sel

f In

tere

stin

g f

rom

VM

D

esig

ner

's V

iew

po

int?

•T

he S

elf l

angu

age

is s

o ex

trem

ely

dyna

mic

that

th

e im

plem

ento

rs h

ad to

pus

h th

e lim

its o

f VM

te

chno

logy

ver

y ag

gres

sive

ly:

–A

dapt

ive

com

pila

tion

to s

peed

up

exec

utio

n.–

Gen

erat

iona

l gar

bage

col

lect

ion

(orig

inal

ly in

vent

ed b

y D

avid

Ung

ar in

his

Ph.

D. w

ork.

)–

Dyn

amic

deo

ptim

izat

ion

to a

llow

deb

uggi

ng o

f hig

hly

optim

ized

pro

gram

s.–

Nov

el c

olla

bora

tive

/ vis

ual p

rogr

amm

ing

and

debu

ggin

g en

viro

nmen

t (tig

htly

inte

grat

ed w

ith th

e V

M.)

•M

any

of th

e ke

y te

chno

logi

es th

at a

re u

sed

toda

y in

mai

nstr

eam

Jav

a vi

rtua

l mac

hine

s w

ere

inve

nted

by

the

Sel

f gro

up.

37Java

•D

evel

oped

by

Jam

es G

oslin

g's

team

at S

un

Mic

rosy

stem

s in

the

early

199

0s.

–ht

tp://

java

.sun

.com

/peo

ple/

jag/

gree

n

•O

rigin

ally

des

igne

d fo

r pr

ogra

mm

ing

cons

umer

de

vice

s (a

s a

repl

acem

ent o

f C+

+).

–U

ses

a sy

ntax

that

is fa

mili

ar to

C/C

++

pro

gram

mer

s.–

Use

s a

port

able

virt

ual m

achi

ne th

at p

rovi

des

auto

mat

ic

mem

ory

man

agem

ent a

nd a

sim

ple

stac

k-or

ient

ed

inst

ruct

ion

set.

–C

lass

file

ver

ifica

tion

was

add

ed to

ena

ble

dow

nloa

ding

an

d ex

ecut

ion

of r

emot

e co

de s

ecur

ely.

•A

gain

, gre

at ti

min

g: th

e de

velo

pmen

t of t

he

Java

tech

nolo

gy c

oinc

ided

with

the

wid

espr

ead

adop

tion

of w

eb b

row

sers

in th

e m

id-1

990s

.

38Sam

ple

Jav

a C

od

e

clas

s P

eg {

int p

egN

um;

int d

isks

[ ] =

new

int[6

4];

int n

Dis

ks;

pub

lic P

eg(in

t n, i

nt n

umD

isks

) {

p

egN

um =

n;

f

or (

int i

= 0

; i <

num

Dis

ks; i

++

) {

di

sks[

i] =

0;

}

n

Dis

ks =

0;

}

p

ublic

voi

d ad

dDis

k(in

t dis

kNum

) {

d

isks

[nD

isks

++

] = d

iskN

um;

}

p

ublic

int r

emov

eDis

k()

{

ret

urn

disk

s[--

nDis

ks];

}

}

39Wh

y is

Jav

a In

tere

stin

g f

rom

VM

D

esig

ner

's V

iew

po

int?

•M

ost p

eopl

e ha

d ne

ver

hear

d of

virt

ual

mac

hine

s un

til J

ava

cam

e al

ong!

•C

ombi

nes

a st

atic

ally

com

pile

d pr

ogra

mm

ing

lang

uage

with

a d

ynam

ic v

irtua

l mac

hine

.

•T

he J

ava

virt

ual m

achi

ne (

JVM

) is

ver

y w

ell

docu

men

ted.

–T

im L

indh

olm

, Fra

nk Y

ellin

, The

Jav

a V

irtua

l Mac

hine

S

peci

ficat

ion ,

Sec

ond

Edi

tion,

Add

ison

Wes

ley,

Jav

a S

erie

s, A

pril

1999

.

•A

JV

M is

see

min

gly

very

eas

y to

bui

ld.

•H

owev

er, t

ight

com

patib

ility

req

uire

men

ts m

ake

the

actu

al im

plem

enta

tion

very

cha

lleng

ing.

–M

ust p

ass

tens

of t

hous

ands

of t

est c

ases

to p

rove

co

mpa

tibili

ty.

40

Des

ign

ing

Vir

tual

Mac

hin

es

41Ho

w a

re V

irtu

al M

ach

ines

Im

ple

men

ted

?

•V

irtua

l mac

hine

s ar

e ty

pica

lly w

ritte

n in

“p

orta

ble”

and

“ef

ficie

nt”

prog

ram

min

g la

ngua

ges

such

as

C o

r C

++

.

•F

or p

erfo

rman

ce-c

ritic

al c

ompo

nent

s,

asse

mbl

y la

ngua

ge is

use

d.–

The

mor

e m

achi

ne c

ode

is u

sed,

the

less

por

tabi

lity.

•S

ome

virt

ual m

achi

nes

(Lis

p, F

orth

, Sm

allta

lk)

are

larg

ely

writ

ten

in th

e la

ngua

ge it

self.

–T

hese

sys

tem

s ha

ve o

nly

a m

inim

al c

ore

impl

emen

ted

in C

or

asse

mbl

y la

ngua

ge.

•M

ost J

ava

VM

impl

emen

tatio

ns c

onsi

st o

f a

mix

ture

of C

/C+

+ a

nd a

ssem

bly

code

.

42Typ

ical

Hig

h-L

evel

Arc

hit

ectu

re

Har

dwar

e

Ope

ratin

g S

yste

m

Virt

ual M

achi

ne

App

licat

ion

43Vir

tual

Mac

hin

e D

esig

n

Co

nsi

der

atio

ns

•S

ize

•P

orta

bilit

y

•P

erfo

rman

ce

•M

emor

y co

nsum

ptio

n

•S

cala

bilit

y

•S

ecur

ity

•... T

here

are

alw

ays

trad

e-of

fs in

VM

des

ign!

44Vir

tual

Mac

hin

e D

esig

n

Co

nsi

der

atio

ns

•U

nfor

tuna

tely

, for

nea

rly a

ll as

pect

s of

the

VM

:•

Sim

ple

impl

ies

slow

•F

ast i

mpl

ies

mor

e co

mpl

icat

ed•

Fas

t im

plie

s le

ss p

orta

ble

•F

ast i

mpl

ies

larg

er m

emor

y co

nsum

ptio

n

–E

xam

ples

:•

Inte

rpre

tatio

n•

Mem

ory

man

agem

ent

•Lo

ckin

g/S

ynch

roni

zatio

n•

Dyn

amic

com

pila

tion

45Co

mp

on

ents

of

a V

irtu

al M

ach

ine

•T

he c

ompo

nent

s of

a v

irtua

l mac

hine

var

y co

nsid

erab

ly d

epen

ding

on

vario

us fa

ctor

s:

–Is

the

lang

uage

inte

ract

ive

(Sm

allta

lk, F

orth

) or

non

-in

tera

ctiv

e (P

asca

l, Ja

va)?

–D

oes

the

lang

uage

hav

e re

flect

ion

capa

bilit

ies

(can

yo

u in

spec

t or

mod

ify th

e V

M o

r th

e pr

ogra

m w

hile

it

is r

unni

ng)?

–D

oes

the

VM

nee

d to

hav

e pe

rfor

man

ce th

at is

co

mpa

rabl

e to

non

-inte

rpre

ted

syst

ems?

–Is

mul

tithr

eadi

ng s

uppo

rt r

equi

red?

–Is

the

VM

req

uire

d to

run

in a

“sa

ndbo

x”?

46Exa

mp

le:

Co

mp

on

ents

of

a Ja

va V

irtu

al M

ach

ine

(JV

M)

Mem

ory

Sys

tem

and

Gar

bage

Col

lect

or

Nat

ive

Inte

rfac

eIn

tern

al R

untim

eS

truc

ture

s

Thr

eadi

ng S

yste

m a

nd T

hrea

d S

ched

uler

Inte

rpre

ter

and

Exe

cutio

n S

tack

s

Cla

ss L

oade

r an

d JA

R R

eade

r

Com

pile

r(o

ptio

nal)

Ver

ifier

47

Cas

e S

tud

ies

48Th

ree

Ver

y D

iffe

ren

t V

irtu

al M

ach

ines

•R

uka:

A m

inim

al, p

orta

ble

For

th v

irtua

l m

achi

ne.

•K

VM

: A J

ava

virt

ual m

achi

ne im

plem

enta

tion

inte

nded

for

smal

l dev

ices

.

•S

quea

k: A

feat

ure-

rich

publ

ic d

omai

n S

mal

ltalk

im

plem

enta

tion.

49Ru

ka:

A P

ort

able

Fo

rth

VM

•W

ritte

n in

AN

SI C

.

•5,

000

lines

of c

ode.

•M

inim

al e

xecu

tabl

e si

ze a

bout

17

KB

.

•Li

ke a

ll F

orth

sys

tem

s, a

llow

s in

tera

ctiv

e de

finiti

on a

nd in

spec

tion

of fu

nctio

ns, a

nd

prov

ides

unr

estr

icte

d ac

cess

to th

e un

derly

ing

oper

atin

g sy

stem

.

•P

orte

d on

to v

ario

us s

mal

l dev

ices

(Pal

m O

S, P

ocke

tPC

, Sym

bian

OS

, ...)

.

50KV

M:

A J

ava

VM

fo

r S

mal

l Dev

ices

•W

ritte

n in

AN

SI C

.

•V

ersi

on 1

.0.4

: abo

ut 3

5,00

0 lin

es o

f qu

ite w

ell-c

omm

ente

d co

de.

–A

bout

50,

000

lines

if d

ebug

ging

sup

port

, nat

ive

func

tions

fo

r th

e J2

ME

CLD

C 1

.0 li

brar

ies,

and

som

e ne

twor

k pr

otoc

ol p

rimiti

ves

are

adde

d.

•F

ully

com

plia

nt w

ith th

e J2

ME

CLD

C te

st s

uite

.

•M

inim

al e

xecu

tabl

e si

ze a

bout

70

KB

.

•P

orte

d on

to n

umer

ous

com

mer

cial

mob

ile

phon

es a

ll ov

er th

e w

orld

.

http

://w

ww

s.su

n.co

m/s

oftw

are/

com

mun

ityso

urce

/j2m

e/cl

dc/d

ownl

oad.

htm

l

51Sq

uea

k: A

Pu

blic

Sm

allt

alk

VM

•A

com

plet

e, c

ompa

ct im

plem

enta

tion

of th

e S

mal

ltalk

-80

Spe

cific

atio

n.

•In

clud

es a

ver

y ric

h gr

aphi

cal p

rogr

amm

ing

envi

ronm

ent a

nd c

lass

libr

ary.

•T

he c

ore

VM

is a

bout

35,

000

lines

of C

cod

e.

•A

com

plet

e ex

ecut

able

with

all

the

grap

hics

lib

rarie

s an

d pl

ug-in

s is

abo

ut 1

MB

.

•V

ario

us p

orts

ava

ilabl

e.

http

://so

urce

forg

e.ne

t/pro

ject

s/sq

ueak

/

52Mo

re In

form

atio

n

•V

irtua

l mac

hine

des

ign:

–B

ill B

lund

en, V

irtua

l Mac

hine

Des

ign

and

Impl

emen

tatio

n in

C/C

++, W

ordw

are

Pub

lishi

ng, M

arch

200

2

•D

esig

ning

“sm

all m

emor

y” s

oftw

are :

–Ja

mes

Nob

le, C

harle

s W

eir,

Sm

all M

emor

y S

oftw

are,

A

ddis

on-W

esle

y, 2

001

•C

onfe

renc

es a

nd w

orks

hops

:–

AC

M S

IGP

LAN

Wor

ksho

p on

Inte

rpre

ters

, Virt

ual

Mac

hine

s an

d E

mul

ator

s (c

o-or

gani

zed

with

PLD

I C

onfe

renc

e), J

une

2003

.–

Use

nix

Java

Virt

ual M

achi

ne R

esea

rch

and

Tec

hnol

ogy

Sym

posi

um (

2001

, 200

2, 2

004)

53Fo

rth

com

ing

Lec

ture

s

Mem

ory

Sys

tem

and

Gar

bage

Col

lect

or

Nat

ive

Inte

rfac

eIn

tern

al R

untim

eS

truc

ture

s

Thr

eadi

ng S

yste

m a

nd T

hrea

d S

ched

uler

Inte

rpre

ter

and

Exe

cutio

n S

tack

s

Cla

ss L

oade

r an

d JA

R R

eade

r

Com

pile

r(o

ptio

nal)

Ver

ifier

24.9

.

17.9

.

1.10

.

8.10

.

8.10

.

29.1

0.

Sess

ion #

2026

: J2M

E Plat

form

, Con

nect

ed Li

mite

d Dev

ice C

onfig

urat

ion (C

LDC)

Qu

esti

on

s?

Sess

ion #

2026

: J2M

E Plat

form

, Con

nect

ed Li

mite

d Dev

ice C

onfig

urat

ion (C

LDC)

ante

ro.ta

ival

saar

i@su

n.co

m