Module-2

Assemblers
Syllabus

• An assembly language is machine dependent, low level

programming language

Input Assembly Assembler Output Machine Language Program and

Information to the Loader
Language Program

• Basic Features of Assembly Language Program

1. Mnemonic operation code
2. Symbolic operands
3. Data declaration
 Elunnts AssembyJamua Pragam
An amemby looua e is amachine dpendadt
tis O low loveN ProgrammInq lanouaye yuh
Sspejic o a Leutain computk sysew

Eprovicuy -hrur baic feadine! Leh Siplty

09 ram mong
N

Mnmmnic Opencuhen Codi ebmales tta

ud o 9LLnO4c oDekation (odos
memorize

b)J enoblus the asembler -o proviele halttu

aluegnostics (exum plo -NISspelt operetton codal
)mboic opevcunols Syuboli MOmLs Cam- 0&

693o ciathd with data r ins tsuuctions

a Sywmbolic nawmus eanbe wed al peTands
in asembly 3-tatemeuts
bThe cLs embler pererms Mimy 6indings
o thSe m
he pr mn need not enaber any
delails 8 th mamry bindings pertumad
by tho aembler
Data ol clara tien Cu be done u i u
lLcimo otutom

Stotmeut ftrmat
Lab ed opcode> opevand spec>,Zopermnd
pec

Ophiomal
a label 1o specrhed i n a Stedontnt,
t1S askouialud as a Symba uc nam
o1th themeMy uoorclscenenatid fr tho
letemowt

Syntax Opexane cpec

Symbei mme +Zdicptucemiuty||indox veqise
 Examplo Opescund ftr ms
AREA AREA+5APEAC4) and
AREAt5(4)
aAREA 1tnefers oth mnemeny WCrd
Lith-ohuh the name AREAISaKo uicttd

bALEA+5 tzfes ts themooy w ere

5worc AA).c frmthe tora bIth
thenoUme A REA He 5 An
displacememt a t set rom K EA
CAEA(4). The 0peTamel adld reR 1S
obtcuee by Lol dihazt Cond éuts a
indexreqiste t. to tha addrru
sALAY,
ArER 5 (4) Jti Combiechion
D une' C

A Sim l akCmb.yauguage
E a c h sttomeutt ha two Operuds
opexuuds
Hrs operamd is aluuayC C eo t
hich Cam be CMN ne
ALEG6REG CREG dael DREG

Se.ccnol Ope ne1s ttcat e e r to a

emoy0crcd uslu Sqmbolc
OMe cn Opional chplacum t
olexi ngic mot penmited
 U l

C A

E
 n ma.cine Leuneuo 4 pTogTam We
aho all aold ressenand constads in
dLttmad Tath thevn in_octal or hexade i
nstauchen tcmot

sigo p code
mu4eny dpexauO
Opesune

Sih isno a pot oj instruction.

The ConcltH ten Lo tn BC
CnLo deid mto-the irst
statmentsis
iug he code openand poS
pos Irficn
Iticm
to', -for f LT, LE etc
LT- LE2, E-3 GT=4, CE-5, ANY=6
Assembly lauguage Poqan Machineleuguase ogau
TART
READ N lo1) 09 0 13
MOVER 8REG, ONE t 042 115
MoVE M BREGTERM fo3) to5 2 11 G
AGAIN MULT BREK, JE RM 104) t03 2
MOVE R CREG,TERM 105 +04 3
ADD
116
CRE6, ONE 106 +OJ 3 15
MovEM eRF,TERM 10 +05 11
LOMP CREG, N +06 3 113
LE, AGAIN ro) +D 2
MoVEM BREG,RESULT t05 2
PRINT RESULT
STOP I12) +00 D 000
N DS 1 113)
RECULT DS 1 14)
ONE C P 115)+00 0 001
TELM DS 116)
END
 Ass embly
quase
N
Sfatzinuts
P5
An
aembly poAscim Consi-s thuenind!
Statemots
mp erati ve Strutomouts
2 Declarution 3tuttneus
3. AsSemblo DIrechiveJ
mpenaive Statumuts
tindcaty the uchon to be perfoomod duwig
the exeticn o the QR embls progTam
Eachlmpeocfive Sloctomeut tanslatiyYnto
madhine nsu-Hon
START 0
1avER READ N roi)+09 03 I13

mpooive Ftcuwiou
naMembly lauquage

2.Decldnactiun Statemeuts
Syndax
Label DS alue
Cen&tt >
LLabell DC

bS Declu Slerae t sesewes htau

C memcY amo aLto.cicutes hemam
ththom
A DS
eXcumpl G DS 200

he firstslatument vesenwes a memo ala

o Were anel akoialls h moime h
with t
The Gecond ctutemeul esenves a block
0 D mumeryWoY CLA he ctdere
reime G
ociaud th fi
werd the bbk.
6lo
sets from G. Ke Cat5 LCom beaceRed thobugl
SIxth 1
 DC Declare constant Eccn&tud
memor y WorcLA contaunno nfruuts
e ONE DC

Thi Sttem eut CusOucLteß ee noLm WE

with a memo y Ore Contcuw t h talu

detlanl
po10m can costayautsin drtlenod
ole.cim.cl biney hxadle.ciml.
1he cSS emblay CoN vents nem to
appopric lL1twna ferm

Ltenals
Hisan Cponand Wth tu suntay Nalud
tennt bet COndt CMo Lenal
Locaticn o_o uteaad_con not ie. Specied
spectfied
nthe as3enrby pi0 m
Hemets Vauue s not cheuyed olwug
exe.cucicn Hu psoqay
ADD AREC E/VE
exumple: ADD AREG,5
t evol FIVE Dc 5
e 5

Th cSembler_oullo cateja9nemeny Oord -t

Contulnhe
-theVoluue utez ue
eplaus the we l i t n_a oalm eut
byanopexund expakicn efeThq to h d
Ocrd
The mame amal addes o hy oord n
KhDWn to u pogbMmeheute t vlus 6 a
iteral prote.cH-lcd.
 ACSemblea Direcivy
HSSemblr durectivesinstruct -the assemb le
0 pexdrn cettain actien owing ths e g
pogTan
STARI Kcanstant 7
hd lre cive mdicat thatthe first uWcd
Bhe tanget po nealid by the
Q8embler should 6e latad m the
ma sorolwitth Addhis censtent>

esign specrficatien cun Assemblor

fow gteps
clentiify the infermaticn meceKary to
penterm a task
2.Design a sutableclata strueture to
e the mfefmation
3 Dexeamine the procy Kinq eces ayto-
obfdn Cmd mumtayn - efeAynatiem
Detminl ta prok)ngnLCeRary to
pehorm t h e t a e k

wo p.hoises
S y nthsis hewse
2 Anelucis Phode
Syhthesis hou e
MOVER 8LEG ONE

To Suthtsize he machint instruckicn ren,

thisstatemiut the follouwtug lnetAmatiln
1s Tequue o_
 Addre the memcy Ocol wrh
hnaume ONE 1S 8 Ocieod
Machine
to the
to
openation Coolcoa o4fPon cli
the mnemenic MOVER
maol
This n-fermacbun IS CWeLi loeble by the
Analysis Phase as t duponel
Sounck p19CMTn
Thi infr maticn cam be
e oltoominady
sywthusis p ede bccauwe
ede
iE IS
ot clependut cn
Two dote structws3 a ed.
Dota Structwy
Symbol Table 2 Mnememics Table
Synako Tabu
Each eutoy had two
name Auel i oleheykmoy field
The
Aubleisbdltbyanaly is phue
Mmemcmics Table
An enty hes
two p(ImY
AnLÄCnits Osndl Opcddo
e Tu Synthuis thale we
obtaia- Hoe nocuvs thase-tables
tablessts
Ohicha nam sasloicted acdoreyLOrth
mAALu 0pLodecomejpendinqDa nd th
Mnem.cmic sApcctivel,
 Anauysis hade
fg-9
hlh mnoun funchin o
Bbtulci.ngo hAse p heule is
the ymbt tabl
+ t hpose t mwb clutermine
cLdclve8e wIÉh uch th Symbouc
eUm u e d in the
progcim TU
Kouicctiel
1 s poscible to dtenminl oma
acldrasej dire ctly ike the adores
he izst ingru ticn n t e progom
bwt ohe adelrRe muut bé ifemed
Tooleteamin thL oLddre o N we2
muwt-ix th add reu a l l proq cn
Qlum pe ceeding Thu (aunctn
calecl nmemjUallecaticn.
Data structu Usee

Locaticn Co uster Lc
t 1s Med to Implemot me mery allocati
Centeins_the helel re thnoxt
memcY 0e - the
TEis tartiali zed t o
proqLM
tanget prog TL
tte Contelt
Specified in th START 9trtomnt
How LCWcaks22
Whene ve Hae oLnalsysisphaleSee_a lal
n a 4 0 Aembly statamLut,itentes
i nel cotemk
Lc bn
e y i n He qmbol teble henthe
no mAn.cr ncdk Teauired by
oS e b ls sldimeuts 1sfoúsaoondHhe
CEmtLpts L i s updatd
Thia hkuhts hat L poats to heMet
yaumo1y od ia th tahget pragm
 L pToCn

To pclat the comteutr L anaty

phole heecs bo kuD the lanetnsd
Afforet instrucHcs. hyinfermactia
depeels CntholseamblyLan ege
Ih Mnemenics tuble Cctn hakie afield
as tengthOichcan holdtt long-th
t in tructiems V
TR pro.ce mu wttudng he LIS
KMDwn as Lc P OCLKin

txemple elata Strutwu wed

Mnemoni Opcode longth
ADD O

SUB o2
Mnemcnits Tasle

Sownu AnalysiS y nthesis Taseet

Pgpam Phodie Phove Prodra

Symbol1 AclroR
AAIN o4
N N 13 Dack k tcess
Control rusfo-
su mon Table

n e m cmics Table Is acceKed by 6othh

auialysis0mel&ynthsis phle
Scbo Tab leis onlcuted dlurung
OMedysis heue cLno edclwll.
Synthiyis phoule
 Pas Stutw Pa-1
Single Pa rmlation
tLCproceMig Is peaermnd
Symbols_ele cleinddin h pgcm Ah
nlled n h mbol 4uble V_
y
5
heOperand field of_cn iul ruction
Ccmttuniue a fANaNd Teteiu 1ss
letblauk nitially
4Theaddxel o te ew aro 4ee ced
t
Lymbol piut iuto h fieldL 0hon_tr
cliwttonic encoLuuten od

This 45
This theferwounel eteenc pro6lem
MOVER BREG, ONE
Ihe instouchon coTes pencliuq to the
Cutimt ea be ily
SyihUsiTed neeSinte
a
pahtially
ONE is" q
ferwane reteenl
Hemce he 1.n8truchon Op coolemd
ad dre BREGwill be alembkd
to Tesicle iu c a t n
Tw pas tcunslaticn

t C haumelle fahanel eferoalia eaily

Pass 1
LC To ceLSnuq ispeafeamed in tirst po
Symbols oluincd im th_prog7m
entned Int he Lymbal table.

PoS 2
n pas ychesi testt tnget ferm
wng heaeld re3 inftrmati onl fo unol
I e &y mbo)-osla

Thehrstpas Constru cB an inlemeda

ep esemtation the Sounu pr0qscumn
eue by Seccmd p a s
Thu utu medint epreentaticn
COndIss two man Compmehb
Dcta ctouctunes Symbol table
Pro.cos.eelferm d he3o p7
LOhich1_calld a itenmsdidtr cod
Data Strutuley

Soe Phoue I Phoue I Toge

Prosan

mBemcduate tol
D acta accee
ControlCntje
 Deincatwo pass aemblen Pg-3
Pas 1
perfos ms oUmalys
pxOgm melSy nthosis
Topentation into mediat
Pats a Po tuges
40 Sntho e -the
the teineclicuti 1epveJerhtc
t et pro qaum
TAks
perfemaoby twopal oenblej
Sepatat tho Symbol, mntmun
0pto cle nhad o peaamd fields
2. Bu lol the Symboltoble
Penferm LC pro CKInq
Conttu Ct uteameold) se presexdoi
Po Synthesire h-laqet pr09sum

To ndonstart the disiqn dteus

aKemmbler pousKe d vehtd_af enblex
odirechive Ckes ORLGN,LTDR G
meeckto be nelenstoolane
ts 1nluuc
emLCpro cRARInoiC alda Ye qureol
ORIGIN

Sytak ORIG IN addxe3 Spec

actcla specIs am Coperand specor kconateunt
Thu ourettiveiuolcatej that Cshe Md te Sek
to 4he dldrekgiven by 0ddseM spec
t h tungek poqzam cloes not Consit
CenseCwtive meimcol lerds then RI6IN
3-ctement is LAE becaue abili
Lo_Ak Copead spec 10kich alouttp dlo L
pTOCLi n elatlve man he) c tn_
 xmp
bet START 200
LOOP deos-P 200

LA-ST STOP 24
ORIGIN LooP +2

Of1OINN LAST+

The glet addry poqTom

aShotem.eut No. 1thseaddres s 2.00
.e
DLIGINLooP
he
+2 ets Lc value fo 204
cause Looin Stutumeit
cddraU 2.02-20.2+2 204)y h
Stotemtnt No. 2.0
LC aue OR1.G1N LAST+ 9A
to214 be cause LAST
no hes addse 2l Skdismin
l6
LTDRG
iAlexcl can be treated ol,a (value
noDC(cluc laue Coni tant )stectumut
O memdT y W.cl Com fei' nire
vau th
theütera is fesro cd
This memay wcacd 1S
uwecd os
in plaL tho literl theope7und
2ThLTORG ctutlnLnt, pe)mits
progammthto spc.cfy hee 11leu
shaduld be place.c
Bycdetdt, asSemble places the lterals
otnEND Stalemmt
Thecuenmb eaallocales momay to he
teralyGa itenal posl
Ihpool .ccmuins.al atuaalsWed in hu
proq sam Cinth Sta or sine lalt TDRG
stottmewt
 Exomplu P-1S
STAOT 2-00
MOVE R AREG,='s
ADD
CeEG,E'T| 204
13 LTO RG

2/1)
2 (2)
15 NEX SUB AREG, 214

24 END
25
219

The iterals are preJemt in ine no. 2 and6

ie 655 a n d 4 c e j e ane addkd to t e
utex peol in stutemeuk i22ana 6 respecfivey
Thefist LTORG Statimuut tn e 13
allo cal add res 11 r 5 amd
212 o Ehè Valu C,',
Ae teralpool Is strvdeo,
e Vclu - 6 1 i s put1n the pos ialin
Mo 1S Th valu is allocatad ths addras
219 d hulu pxo.cting he END

Examnp le Tornand Rife^enc

The iteral -*1 in ut a. 15 relen to

Locatin 219 c the Se comd ool literde
gathetheun Locatien212 firgt poo
H t Sam ISHae calewrth 5 5
un
w no.
mu. 2 Lo Catiem
Crocotlon 212)
21 aMd in
Thuu aU yedeNLht to iteTals a ferwd
fesenenuy 6y oufinthon-
 EpU
Syntax Sy mbol2 EqU addre spec
oheneadlelses Spo is an ope ramd spec)
o constantt

th E(QU latmeut deline4 tu y ubol

o
apredent <add ra Spec
EQU asoi atu e name LsymbelS
OclolreAL SP ace
Engmp l

2
STA2T200 200
LooP MoVER ARFG,A g02) +04 214

BC ANNEAT 24 +0 21y-
21S 40 202
22 BACK EDV LooP

Tn inntno22 EpU_assoCials thenoml

BACKto e Aet thi syabol, Loop
So Une wo 16 I S AAeusblod _ay
202
Inhruchon, Opcodt
Bocatin B c R istr Lo-tation 0 LO0P in line , y_-
Opiode
ALEh 4A 21
 Pas h asembler P-1

Thoolowinqolocta structu oe ued

OPTAB is a lablo o henonut Cpcodls

mel related ormatiun
SyMTAB Symubol-leble
It LiTTAB A talole tenali ued in

thpro4ers

Examp
Sonple Psoq sam

START 200
MOVER A Ea'5 200 F 1 2
MoVEM ALE, AA 201) t05 2)9
3
LoOP M0 VE AREG, A 2 2 to / 2/
203 +O5 3 2)8
MOVER CREGB
cREG, = 20 +o 2/2
ADD
07 6 2/
12 BC ANY,NEST

13 LTOLG
o05
211)
2 f0o O0

NEAT SUB ALEG, 214 +02 21

202
BC LT, BAC
216) +00
1 LAST STOP

1 0PGA LOOP+2
201)t0 3 218
19 MULT CREGB
ORIGIN LAS T+L
20
21 -
21
22 BACK EQU LOOP
23 B 219
94 END
25 21 +00 0 0o
 he tab le o oladat uctwre 0 9
OP TA Bcontains he fielckmnemonu
optode, cla mnamcmic no
Contcu
a)Mnemonic Opcoos,Tustution mnum onls
bClu I indicouLohethun h s
Mnemm opco d anéan
Coelp omolu to aun
iMpatie SHoutiëment 1s)ora
cletlaraticm
C-tuutemet (DL Or an asenb Lor olure
Mnemenic 1nft> Fer TS:-he ctise (AD)
o ComSists paù
m.nemcmtc
in&toudion length. ma h o oplD olo
Fr DL
kis sield contene jol o the
7 For AD
o hanele tthe eclara Hcm zoutia
C oulsembley ve CH
ve
SHelomod
MneMeniL op cDelu clak m ne Onc /o
MD VEER
DS
1S 04,
STAej
DL R#
AD

OP TAB

2 SyMTAB Corrteuns addyess_cnal lenath.

cwonguit Ha Symbdl elol
Sy mbol AddeKlenyth
LooP 202
NEKI 214
LAST 2-16
A 21
BACK 202
218
Sy MTAB am
 LITTAB L P-19
centaun titeyul
LITTAB and acld xe leldl
uterad aoldres
5'

-Aaunes ocferet utnala

matoned poðls 1S
He auxua
Kubuwn as P00LT B ebl

PooLTAB consist a Literal no,

Lite >al no Statina Litpnal
#L each pool

Pro csI ng

Poousiughots wth labelielel

1 t cohtains &4mbol, #e cybol dond
th Palue in Lc copie t a d new edy
o Sy wtab.
. Thntuntiening sPas 1 teA sep certis
ano.wnd H imdenp retatio a h OP TAB
ety er He men.cmi
i he clas field cortaunsS thn eng of
the mpchine ustuchnis aeleled to Lc
ThA Lemath ialso entend tn Symtab.kdrpabol
eutey T ymbolHhed in th i stomud
6 tie clam ield cntuwnsDL o AD hsn th
qowtin tmticmaoI he mnomomic infofield
s callee to peaform-apprepTittprieekig
-B Rtatemeit
Fox DL h T0utine proceALes th 0pe rand field
s thglatumest t dete rmine tie ampunt
 memny Te4ured byDL steitemant a
CAppropialely updelis e LC d Symtalb
e r y o t e Lymbol dapined in t tattm
iFor AD, the caloolYo uctine Oould pontem
Cuppropriote prousI Okic h o-ffecfs -the
Vaue m'L
6 Next, TTAB omo Po0LTA B a eo
AL a y gtuge e
ts h e
Le
cwhrotUteral pod1
pool n LT TAB
On e n CO tejuq
END statoALAt_ terals inthe
LTO2 stalemlut
Cwnet pool are alocatid addresse
on toih the Yalue in 10
awel tc s c p propTinly inC Yemeuteo

Eldde Flpekt Algcnthe

o s s emnblar p s Visive
g-
For e in tuo D p aLsembliu,
iwtnurellt Co e m L petu
lutenmeadietr odk ornms
lupo_csitua to chvese intemeoliati od
Pro cusineftiuemy
MLMOy cmomy

nterMLelic CoclLe Conists Set

T C A t s eah IC unE pcnlis ng
th -0|lowln twrtL frelcls
AddresL
RLpRAeutatum aMnemcni oPLadi
Lepreseudakicn spe nds
AdcdroA Opcode| opcranods
 Pa-21
D to troLeleo
u l to between p1o csin etileuy
VUcut
Cne mmUy eco nomy, two
Intermcoluau codss u thaN

Vol w amd VouMut LL

aMumed
Hgumptiun Tue cudclee fie ld is
ticolmfamatim i
0contain
both vwdadts.

is Tep
TAAuted by a
The first Operand
w is a
unben
Sing ligit (-AREG,2-B2EG, 3. .,4
eqste). ANy
itself - f r LT-
C
coclL
Conditlom
perumd 1s memoTy p e r o n
Tue Se como
Teptesended b
pC
When perana
term opevcund tlcss,ode Sy mbol(s) C
Cmtcumt C )
The cocle field s t t e uterreJ
literal (L)
epseJentuti o he C n UF opsruneclasg C)

exwmp

START 200 (AD, O1) ,200)

READ A (Is,01) (s, o)
Lo OP MoVE ALEG,A

SUB ALEG, s0
BC 6T, LOOp (2S,0) C4) (S,o2)
StoP Ts,00)
 Vauoum 1
2peromod elcd o sowu statmaut
cue SeluchelLy
ProcA&ed fermn by
Fos dec laxatise statemints une allembler
drechves procgi u
e cain to cut pkr LCCperanol iel LS
proceliq
kBinperatiestatemLnte
procksed
4 bpevand iele
ny to jeleuti'fy Ulora refelue
Excmnpla
START 200
LEAD A
(AD Of) (C 200)
LOOP MOVER AREG,, A (TS, 01
TS,0y)_ AREG, A
SUB ALEG, =° (1s,02)
G1, LOOP (ES, )
AREG,(L,D)
A
STOP
CIS,00)
GLLOp
D
CAL, D2) Ce,D
LTOLG
AD,05)

Alarthm er Pass I h a aKemble

is ven iwpage-10
habook
In PaA I
aluorithmt is
Mar taqdt code ls to a8
be
umed hat
a98 enblod
in ane a nameod CodL- OLa
Thene . g t be Come cheunges to Sut
i t medot caole eme
Vouu o t I
beiug
(
pesiyn oSingle
Paus Assembler Pa-23

Intel go8? Assembu

olaffes fom pa 1 4
The L procus Ing
uo pa Qemble(
memoy
location isa bvte
the wut tor exumple
Here,
conLsptIS wdeo
LC alignment aolorey .e
acldrey e
must be esen
c l a n t addrey Um eNent bowndove
aluan meut
Wo c e q u i e l c A Ktatment and
o memo
Allocatieni
ladel i t h e
&ymbol tabl is
enung its
oN[Calugn mint
peafurtd a t
Aed
Data Struc tuwu

Mnemenucs able MOT)

1 h a h _icuni zcd
i s
thetollouwjug ields
1t contu'n
monic, Op CDde machine 0pLod,
olugameet 4eimoat vto
Spectfic a
Alnmeutfermat into
ve 0 utlne
outins id ficld a n eutYy specaies
he routirne Dih proces hot Opcodo

MnLwO Matkim nmnt /fomat lodine

OpcooleOpcodu 'Info iel
JNE 15H -0OH 2-
ARmues tasle MOP|

The Lo.cle 00H tox qoutineR2 imples hat

Only en instaution _ermad with sef-selative
dinplaLmut iS Supponted.

tien timple) hot_al umat au luppore

Hen HeOut mut dlcido ouh -årAets
mahe OpLocle to ule
 P
2Sqod fcubk SYMTAB
J s Clgo hash
1E orqamuTLd
centw n allTelevaut indvmatic
abowt SmbDls_definecd ahod
sow . Symos eo in th
eld d
0Onr Seamwti Symbol
Seanevt auuhich
8nabol iduined.
T1pe Fo nLon
IneucaAs th Epu, ih pE held
aan mecl nemaon
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