Macro

First Macro Example:- #include <stdio.h> #define SquareOf(x) x*x void main() { int xin=3; printf("\nxin=%i",xin); printf("\nSquareOf(xin)=%i", SquareOf(xin) ); printf("\nSquareOf(xin+4)=%i", SquareOf(xin+4) ); printf("\nSquareOf(xin+xin)=%i", SquareOf(xin+xin) ); }

C Program for Swapping:- #include<stdio.h> void exchange(int i, int j) { int temp; temp = i; i = j; j = temp; printf("AFTER - %d %d\n", i, j); } main() { int i=1, j=3; printf("BEFORE - %d %d\n", i, j); exchange(i, j); }

Macro for Swapping:- #include<stdio.h> #define swap(i,j) { int temp; temp=i; i=j; j=temp; } void main() { int i=1, j=3; printf("BEFORE - %d %d\n", i, j); swap(i,j); printf("AFTER - %d %d\n", i, j); }

Macro:- A macro is a unit of specification for program generation through expansion. A macro consists of a name, a set of formal parameters and a body of code. The use of macro name with a set of actual parameters is replaced by code generated from its body.

Macro definition & Call:- A macro definition is enclosed between the name of a macro header and a macro end statement . It consists of :- A macro prototype statement One or more model statement Macro processor statement. Macro prototype statement Syntax: <macro name> [<formal parameters>]

Macro Call:- A macro is called by writing the macro name in the mnemonic field of an assembly statement. Syntax:- <macro name> [<actual parameter list>] Example:- MACRO TEST &X, &Y, &Z AIF (&Y EQ &X) .ONLY MOVER AREG, &Y AGO .LAST .ONLY MOVER AREG, &Z .LAST MEND Macro Call:- TEST S,10 Macro header & End stmt

ADVANCED MACRO FACILITIES Facilities for change of flow of control Expansion time variables Attributes of parameters

For change of flow of control:- Two features are provided for this purpose Expansion time Sequencing Symbol Expansion time Statements ( AIF,AGO,ANOP) Sequencing Symbol( SS) SS is defined by putting it in the label field of a stmt in the macro body. Statements (syntax) AIF-> AIF ( <expression>) <Sequencing Symbol (SS)> Expression includes relational expression ( LT, NE etc.). If condition is true then control is transferred to SS. AGO-> AGO <SS>  unconditional transfer ANOP-> <SS> ANOP  used to define SS

Example MACRO TEST &X, &Y, &Z AIF (&Y EQ &X) .ONLY MOVER AREG, &Y AGO .LAST .ONLY MOVER AREG, &Z .LAST MEND REPRESENTING SS If condition is true ( Y= X) then control will be transferred to .ONLY

Expansion time variables EV’s are variables which can be only used during the expansion of macro calls. It may be of two types:- Local EV (LCL) can be used only in one particular macro. Global EV (GBL) works like global variables. Syntax:- LCL <EV specification>, ……… GBL <EV specification>, …….. Values of EV can be changed using SET (preprocessor stmt). <EV specification> SET <SET expression>

Example of EV MACRO TESTEV LCL &A &A SET 1 LCL &A declares local variable A

Attributes of parameters An attribute is written using the syntax:- <attribute name> ’ <formal parameter specification> T– type L – length S – size Example MACRO ME &A AIF (L’&A EQ 1) .NEXT ------ -----

EXAMPLE MACRO TEST &X, &N, &R=AREG LCL &M &M SET 0 .PQ MOVEM &R, &X+&M &M SET &M + 1 AIF (&M NE N) .PQ MEND

EXAMPLE MACRO TEST & X , & N , R =AREG LCL & M &M SET 0 .PQ MOVEM &R, &X+&M &M SET &M + 1 AIF (&M NE N) .PQ MEND MACRO CALL TEST S,10 REPRESENTS PARAMETER NAME REPRESENTS EXPAN. VAR. NAME REPRESENTS SEQUENCING SYMBOL NAME REPRESENTS ACTUAL PARAMETER NAME

Tables of Macro Preprocessor MACRO NAME TABLE FIELDS:- a) Macro name b) No. of Positional Parameters (#PP) c) No. of Keyword Parameters (#KP) d) No. of Expansion Time Variables (#EV) e) MDT Pointer (MDTP) f) KPDTAB Pointer (KPDTP) g) SSTAB Pointer (SSTP) 2. PARAMETER NAME TABLE FIELDS:- a) Parameter Name

Tables of Macro Preprocessor 3. EV NAME TABLE (EVNTAB) FIELDS:- a) EV name 4. SS NAME TABLE FIELDS :- a) SS Name 5. Keyword Parameter Default Table (KPDTAB) FIELDS:- a) Parameter Name b) Default Value 6. Macro Definition Table (MDT) FIELDS :- a) Label b) Opcode c) Operands

Tables of Macro Preprocessor 7. Actual Parameter Table (APT) FIELDS :- a) Value 8. EV Table (EVTAB) FIELDS:- a) value 9. SS Table (SSTAB) FIELDS :- a) MDT Entry #

PNTAB EVNTAB KPDTAB SSNTAB APTAB EVTAB SSTAB R N X M AREG R PQ AREG 10 S 0 27

MNT MDT SSTP KPDTP MDTP #EV #KP #PP Name 5 10 25 1 1 2 TEST 30 29 28 27 26 25 MEND AIF (E,1) NE (P,2) (S,1) (E,1) SET (E,1) +1 MOVEM (P,3),(P,1)+(E,1) (E,1) SET 0 LCL (E,1)

Steps for MNT Entry TEST & X , & N , R= AREG STRUCTURE OF MNT For each positional parameter (i) Enter Parameter name in PNTAB [PNTAB_ptr] (ii)PNTAB_ptr := PNTAB_Ptr + 1; (iii)# PP := # PP + 1 : PNTAB x #pp=1 N #pp=1+1=2 SSTP KPDTP MDTP #EV #KP #PP Name

Steps for MNT Entry TEST & X , & N , R= AREG STRUCTURE OF MNT 10 PNTAB For each keyword parameter (i)Enter parameter name and default value ( if any), in KPDTAB (ii) Enter parameter name in PNTAB [ PNTAB_Ptr}. (iii) KPDTAB_Ptr := KPDTAB _Ptr + 1 ; (iv) PNTAB_Ptr := PNTAB_Ptr + 1; (v)# KP := # KP + 1 ; KPDTAB R R, AREG # KP := 1 N x AREG R SSTP KPDTP MDTP #EV #KP #PP Name

MDT 5 SSTAB MNT 30 29 28 27 26 25 MEND AIF (E,1) NE (P,2) (S,1) (E,1) SET (E,1) +1 MOVEM (P,3),(P,1)+(E,1) (E,1) SET 0 LCL (E,1) 27 SSTP KPDTP MDTP #EV #KP #PP Name 5 10 25 1 1 2 TEST

LCL & M EVNTAB M If an LCL statement then (i) Enter expansion time variable name in EVNTAB (ii)# EV := # EV + 1 ; M

.PQ MOVEM &R, &X+&M SSNTAB a) If SS is present in SSNTAB then get index No. Else 1 Enter SS in SSNTAB, then get index No. and 2. Enter MDT_Ptr in SSTAB b) For a parameter , generate the specification ( p,#n). c) For an expansion variable,generate the specification ( E, # m). . PQ SSTAB 5 27 .PQ MOVEM &R, &X+&M MOVEM (P,3) , (P,1)+(E,1) Enter this line into MDT Steps for Model Stmt

(Processing of a macro definition) 1. SSNTAB_Ptr :=1; SSTAB_PTR:=1;MDT_ptr:=1; PNTAB_ptr :=1;KPDTAB_PTR:=1; 2. Process the macro prototype statement and from the MNT entry (a) name := macro name ; (b) For each positional parameter (i) Enter Parameter name in PNTAB [PNTAB_ptr] (ii) PNTAB_ptr := PNTAB_Ptr + 1; (iii) # PP := # PP + 1 : (c) KPDTP := KPDTAB_ ptr ; (d) For each keyword parameter (i)Enter parameter name and default value ( if any), in KPDTAB [KPDTAB_ptr + 1]; (ii) Enter parameter name in PNTAB [ PNTAB_Ptr}. (iii) KPDTAB_Ptr := KPDTAB _Ptr + 1 ; (iv) PNTAB_Ptr := PNTAB_Ptr + 1; (v) # KP := # KP + 1 ; (e) MDTP := MDT_Ptr, (f) #EV := 0 ; (g) SSTP := SSTAB_Ptr ;

3. While not a MEND statement (a) If an LCL statement then (i) Enter expansion time variable name in EVNTAB (ii) # EV := # EV + 1 ; (b) If a model statement then (i) If a label field contains a sequencing symbol then If symbol is present in SSNTAB then q := entry number in SSNTAB; else Enter symbol in SSNTAB [ SSNTAB_Ptr]. q:= SSNTAB_Ptr; SSNTAB_ptr := SSNTAB_Ptr + 1; SSTAB [ SSTP + q – 1] := MDT_ Ptr; (ii) For a parameter , generate the specification ( p,#n). (iii) For an expansion variable,generate the specification ( E, # m). (iv) Record the IC in MDT [ MDt_ptr]; (v) MDT_Ptr := MDT_Ptr + 1 :

(c ) If a preprocessor statement then (i) If a SET statement Search each expansion time variable name used in the statement in EVNTAB and generate (E,#m) (ii) If an AIF or Ago statement then If sequencing symbol used in the statement is present is SSNTAB then q = entry number in SSNTAB else Enter symbol in SSNTAB [ SSNTAB _ Ptr] q := SSNTABPtr ; SSNTAB_ Ptr := SSNTAB_ Ptr + 1 : Replace the symbol by ( S, SSTP + q – 1 ) (iii) Record the IC in MDT [MDT_Ptr]. (iv) MDT_Ptr := MDT_ Ptr + 1 :

4. (MEND Statement ) If SSNTAB_Ptr = 1 ( i,e, SSNTAB is empty ) then SSTP := 0; Else SSTAB_Ptr := SSTAB_ Ptr + SSNYAB_Ptr – 1 : If # KP = 0 then KPDTP =0;

Macro

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