Macros allow programmers to define abbreviations for sequences of instructions. A macro definition specifies the macro name and the sequence of instructions to be abbreviated. When a macro is called, it is expanded by replacing the macro name with the defined sequence of instructions. Macros can call other macros, requiring macro processors to handle nested macro expansion. Macro processors implement macros using a single or double pass approach to first save macro definitions and then expand macro calls by substituting argument values.

1. MACROS
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2. MACRO
 Macro instructions are single-line abbreviations for group of
instructions.
 Macro is an abbreviation for a sequence of operations .
 Syntax/structure
start of definition MACRO
macro name {
Sequence to be abbreviated }
End of definition MEND
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3. MACRO
 Example
:
:
A 1, DATA
A 2, DATA
:
A 1, DATA
A 2, DATA
:
DATA DC F’5’ 11/15/2016jaya
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4. MACRO
 Example(Macro definition)
Syntax example
MACRO MACRO
MACRO NAME INCR
INSTRUCTION 1 A 1, DATA
INSTRUCTION 2 A 2, DATA
.
.
.
MEND MEND
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5. MACRO Example(Macro call)
Macro call(SYNTAX) macro call(example)
MACRO MACRO
MACRO NAME INCR
INSTRUCTION 1 A 1, DATA
INSTRUCTION 2 A 2, DATA
:
:
MEND MEND
:
INSTRUCTION A 3, DATA
:
MACRO NAME INCR
: DATA DC F’5
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6. MACRO
 Example(Macro definition)
Syntax example
MACRO MACRO
MACRO NAME INCR
INSTRUCTION 1 A 1, DATA
INSTRUCTION 2 A 2, DATA
.
.
.
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7. CONDITIONAL MACRO EXPANSION
 Two pseudo-ops are used
 AIF:- It is conditional branch pseudo-op that performs an
arithmetic test and branches to specified macro-label only if test is
true.
 AGO:- It is unconditional branch pseudo-op. It is equivalent to go-
to statement.
 .FINI:- Labels starting with a period(.), such as .FINI, are macro
label do not appear in the output of the macro processor.
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8. MACRO
: macro definition :
LOOP1 A 1,DATA1 MACRO
A 2,DATA2 ARG0 VARY &COUNT,&ARG1,&ARG2,&ARG3
A 3,DATA3 &ARG0 A 1,&ARG1
: AIF (&COUNT EQ 1).FINI
LOOP2 A 1,DATA3 A 2,&ARG2
A 2,DATA2 AIF (&COUNT EQ 2).FINI
: A 3,&ARG3
LOOP3 A 1,DATA1 .FINI MEND
: macro call :
DATA1 DC F’5’ LOOP1 VARY 3,DATA1,DATA2,DATA3
DATA2 DC F’10’ :
DATA3 DC F’15’ LOOP2 VARY 2,DATA3,DATA2
: :
LOOP3 VARY 1,DATA1
:
DATA1 DC F’5’
DATA2 DC F’10’
DATA3 DC F’15’
Pgm with macro definition
(macro call)
example
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9. MACRO
: :
MACRO MACRO
&ARG0 VARY &COUNT,&ARG1,&ARG2,&ARG3 &ARGO VARY &COUNT,&ARG1,&ARG2,&ARG3
&ARG0 A 1,&ARG1 &ARG0 A 1,&ARG1
AIF (&COUNT EQ 1).FINI AIF (&COUNT EQ 1).FINI
A 2,&ARG2 A 2,&ARG2
AIF (&COUNT EQ 2).FINI AIF (&COUNT EQ 2).FINI
A 3,&ARG3 A 3.&ARG3
.FINI MEND .FINI MEND 3,&ARG3
: :
LOOP1 VARY 3,DATA1,DATA2,DATA3 LOOP1 A 1,DATA1
: A 2,DATA2
LOOP2 VARY 2,DATA3,DATA2 A 3,DATA3
: :
LOOP3 VARY 1,DATA1 LOOP2 A 1,DATA3
: A 2,DATA2
DATA1DC F’5’ :
DATA2DC F’10’ LOOP3 A 1,DATA1
DATA3DC F’15’ :
Macro call
Macro expansion
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10. MACRO CALLS WITHIN MACROS
:
L 1,DATA1
A 1,=F’1’
ST 1,DATA1
L 1,DATA2
A 1,=F’1’
ST 1,DATA2
L 1,DATA3
A 1,=F’1’
ST 1,DATA3
:
:
DATA1 DC F’5’
DATA2 DC F’10’
DATA3 DC F’15’
:
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11. MACRO CALLS WITHIN MACROS
MACRO
ADD1 &ARG
L 1,&ARG
A 1,=F’1’
ST 1,&ARG
MEND
MACRO
ADDS &ARG1,&ARG2,&ARG3
ADD1 &ARG1
ADD1 &ARG2
ADD1 &ARG3
MEND
Macro call
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12. MACRO EXPANSION
SOURCE
:
MACRO
ADD1 &ARG
L 1,&ARG
A 1,=F’1’
ST 1,&ARG
MEND
MACRO
ADDS &ARG1,&ARG2,
&ARG3
ADD1 &ARG1 : :
ADD1 &ARG2
ADD1 &ARG3 L 1,DATA1
: ADD1 DATA1 A 1,=F’1’
: ST 1,DATA1
: L 1,DATA2
: ADD1 DATA2 A 1,=F’1’
ADDS DATA1,DATA2, ST 1,DATA2
DATA3 ADD1 DATA3 L 1,DATA3
A 1,=F’1’
: ST 1,DATA3
:
:
: :
: :
DATA1 DC F’5’ DATA1 DC F’5’
DATA2 DC F’10’ DATA2 DC F’10’
DATA3 DC F’15’ DATA3 DC F’15’
Expanded
source of
ADDS
Expanded
source of
ADD1
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13. MACRO DEFINITION WITHIN MACRO DEFINITION
MACRO
DEFINE &SUB
MACRO
&SUB &Y
CNOP 0,4
BAL 1,*+8
DC A(&Y)
L 15,=V(&SUB)
BALR 14,15
MEND
MEND
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14. MACRO DEFINITION WITHIN MACRO
DEFINITION
 Inner macro will not be defined until outer macro is called.
 Macro call sequence
 DEFINE COS
 The statement expands into a new macro definition
 COS AR
 The macro processor will generate the calling sequence:
BAL 1,*+8
DC A(AR)
L 15,=V(COS)
BALR 14,15
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15. IMPLEMENTATION
STATEMENT OF PROBLEM
SPECIFICATION OF DATA BASES
SPECIFICATION OF DATA BASE FORMAT
ALGORITHM
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16. STATEMENT OF PROBLEM
 Macro processor is a system program which accepts an assembly
language program with macro definition and macro calls and produce
an equivalent assembly language program in which all macro calls are
expanded.
 Four basic tasks of macro instruction processor
 Recognize macro definitions
 Save the definition
 Recognize calls
 Expand calls and substitute arguments
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17. STATEMENT OF PROBLEM
 Macro processor performs expansion using 2 passes
 Pass I
 It examines every operation code
 Save all macro definitions in a macro definition table
and macro name table
 Save a copy of the input text , minus macro definition
 Pass II
 Identify macro calls
 Replace each macro name with the appropriate text
from macro definition(expand macro call)
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18. SPECIFICATION OF DATA BASE
 PASS I
 The input macro source deck
 Output macro source deck copy for use by pass2
 Macro Definition Table(MDT)
 Macro Name Table(MNT)
 Macro Definition Table Counter(MDNTC)
 Macro Name Table Counter(MNTC)
 Argument List Array(ALA)
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19. SPECIFICATION OF DATA BASE
 PASS II
 The copy input macro source deck
 Output expanded source deck copy for use by
assembler
 Macro Definition Table(MDT) created by pass1
 Macro Name Table(MNT) created by pass1
 Macro Definition Table Pointer(MDNTP)
 Argument List Array(ALA)
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20. PASS 1- PROCESSING MACRO
DEFINITIONS
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21. EXAMPLE
MACRO
&LAB INCR &ARG1,&ARG2,&ARG3
&LAB A 1,&ARG1
A 2,&ARG2
A 3,&ARG3
MEND
|
|
INCR
Index Contents(80 bytes per entry)
5 &LAB INCR &ARG1,&ARG2,&ARG3
6 #0 A 2,#1
7 A 3,#2
8 A 2,#3
9 MEND
10
INDEX NAME(8
bytes)
0 #0(&LAB)
1 #1(&ARG1)
2 #2(&ARG2)
3 #3(&ARG3)
INDEX NAME( 8
bytes
MDT
POSITION(
4 bytes)
1 INCR 5
2
3
Macro Definition Table
Argument List Array
Macro Name Table
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22. PASS 2 – PROCESSING MACRO CALLS AND EXPANSION
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23. EXAMPLE
MACRO
&LAB INCR &ARG1,&ARG2,&ARG3
&LAB A 1,&ARG1
A 2,&ARG2
A 3,&ARG3
MEND
|
|
LOOP1 INCR DATA1,DATA2,DATA3
Index Contents ( 80 bytes per entry)
5 &LAB INCR &ARG1,&ARG2,&ARG3
6 #0 A 2,#1
7 A 3,#2
8 A 2,#3
9 MEND
10
INDEX NAME (
8 bytes)
0 “LOOP1bbb”
1 “DATA1bbb”
2 “DATA2bbb”
3 “DATA3bbb”
INDEX NAME ( 8 bytes) MDT
POSITION
( 4 byte)
1 “INCRbbb” 5
2
3
Macro Definition Table
Argument List Array
Macro Name Table
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24. MACRO
&LAB INCR &ARG1,&ARG2,&ARG3
&LAB A 1,&ARG1
A 2,&ARG2
A 3,&ARG3
MEND
|
|
LOOP1 INCR DATA1,DATA2,DATA3
LOOP1 A 1,DATA1
A 2, DATA2
A 3,DATA3
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25. IMPLEMENTATION OF MACRO
CALL WITHIN MACRO
 Basic problem in implementing macro calls within
macros is “recursion”
 Need to expand both macro
 Each call might be expanded by another macro
 More macros vs single macro
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26.  Example with 2 macros ADDS and ADD1
MACRO
ADD1 &ARG
L 1,&ARG
A 1,=F’1’
ST 1,&ARG
MEND
MACRO
ADDS &ARG1,&ARG2,&ARG3
ADD1 &ARG1
ADD2 &ARG2
ADD3 &ARG3
MEND
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27.  MDT(Macro Definition Table)
Index Contents
1 ADD1 &ARG
2 L 1,#1
3 A 1,=F’1’
4 ST 1,#1
5 MEND
6 ADDS &ARG1,&ARG2,&ARG3
7 ADD1 #1
8 ADD2 #2
9 ADD3 #3
10 MEND
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28. IMPLEMENTATION WITHIN AN
ASSEMBLER
 Macro processor can be added as a pre-processor to
an assembler
 Combining similar functions
 Ex- MNT+MOT/POT
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29. MACRO PROCESSOR COMBINED WITH
ASSEMBLER PASS 1
PASS 1!
Search Pseudo-Op Table
(POT)!
Search Macro Name Table
(MNT)!!
GO TO PASS2!
Search Machine -Op Table
(MOT)!
Process machine instruction
Type?
Process macro definition
Set up macro stack frame ,
etc.
Process pseudo-ops
READ *R
R
R
R R
END pseudo-op
Found
others
Not macro call
Not pseudo op
Found macro call
Macro pseudo op
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30. ADVANTAGES & DISADVANTAGES
OF INCORPORATING MACRO INTO
PASS1
 Advantages
 functions do not have to implemented twice
 Less overhead during processing
 More flexible for programmer
 Disadvantages
 Large program
 More complex
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31. SINGLE PASS ALGORITHM
 Problem of macro definition with macros
 Combine pass1 and pass2
 Two additional variables
 MDI(Macro Definition Input) indicator
 MDLC(Macro Definition Level Counter)
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32. One-pass macro processor
MDTC  1
MNTC  1
MDI  “OFF”
MDLC  0
Search MNT for match with
operation code
MDTP  MDT index from MNT
entry
READ
Macr
o
name
found
MDI  “ON”
Set up macro call argument list array
Macr
o
pseu
do-op
?
READ*
Enter macro name & current value of
MDTC in MNT entry number MNTC
MNTC  MNTC+1
Prepare macro definition argument list
array
Enter macro name card into MDT
MDTC MDTC+1
MDLC MDLC+1
READ*
MDTC MDTC+1
Substitute index notation for argument
in definition
Enter line into MDT
Macro
pseudo
-op ?
MEN
D
pseud
o-op ?
MDLC MDLC+1
MDLC MDLC-1
MDLC
 0 ?
MNTC  MNTC+1
END
Pseudo
-op?
Supply expanded source file to
processing
a
a
a
no
Yes macro call
no
no
yes
yes
no
yes
no
yes
no
Yes macro definition

33. READ *
subroutine
MDI =
“OFF”
?
Read next source card from
input file
Return to main processing
Increment MDT pointer to
next entry MDTP 
MDTP + 1
MDI  “OFF”
Get next card from MDT
Substitute arguments from
macro call
Process AIF or AGO set new value
to MDTP
MDLC
= 0 ?
MEND
pseudo-
op ?
AIF
or
AGO
?
yes
yes
yes
yes
No within
macro call
no
no
no
Detail of read function used
for macro expansion
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34. One-pass macro processor
MDTC  1
MNTC  1
MDI  “OFF”
MDLC  0
Search MNT for match with
operation code
SP  SP+N+2
READ
Macr
o
name
found
S(SP+N+2) SP
Set up macro call argument list
array in S(SP+2)---- S(SP+N+1)
where N = total number of
arguments
Macr
o
pseu
do-
op ?
READ*
Enter macro name & current value of
MDTC in MNT entry number MNTC
Prepare macro definition argument list
array
Enter macro name card into MDT
MDLC MDLC+1
READ*
Substitute index notation for
argument in definition
Enter line into MDT
Macro
pseudo
-op ?
MEN
D
pseud
o-op ?
MDLC MDLC+1
MDLC MDLC-1
MDLC
 0 ?
MNTC  MNTC+1
END
Pseudo
-op?
Supply expanded source file to
processing
a
a
a
no
Yes macro call
no
no
yes
yes
no
yes
no
yes
no
Yes macro definition
S(SP+1) MDT index from MNT
entry
b
b
b
One pass macro processor capable
of handling macro calls within macro
definitions
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35. READ *
subroutine
SP = -
1
Read next source card from
input file
Return to main processing
Increment MDT pointer to
next entry S(SP+1)+1
Get next card from MDT ;
pointer is S(SP+1)
Substitute arguments from macro
call S(SP+2)…S(SP+N+1)
N  SP – S(SP)-2
AIF or
AGO ? MEND
pseudo-
op ?
MDL
C = 0
?
yes
yes
yes
No within
macro call
no
no
yes
Process AIF or AGO set new value
to MDTP
SP  S(SP)
yes
no
b
b
Detail of read
function for
recursive
macro
expansion
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