MACROS Suthida Chaichomchuen

Purposes  To simplify and reduce the amount of repetitive coding.  To reduce errors caused by repetitive coding.  To make an assembly program more readable.

Functions that implemented by macro  Input/Output operation that load register and perform interrupt  Conversions of ASCII and binary data  Multiword arithmetic operation  String-handling routines

Format of macro definition macronameMACRO [parameter list] [instructions] ENDM ;Define macro ;Body of macro ;End of macro

Simple macro definitions INITZMACRO;Define macro MOV Body MOV DS,AX ; of MOV ES,AX ; macro definition ENDM;End of macro

Simple macro definitions FINISHMACRO;Define macro MOV AX,4C00H ;Body of INT 21H ;macro definition ENDM;End of macro

Using parameter in Macros PROMPTMACROMESSAGE;dummy argument MOVAH,09H LEADX,MESSAGE INT 21H ENDM;End of macro

Using parameter in Macros MESSAGE2DB‘Enter the date as mm/dd/yy’ PROMPTMESSAGE2

Macro Comments PROMPTMACROMESSAGE ; This macro permits a display of messages MOVAH,09H;Request display LEADX,MESSAGE;prompt INT 21H ENDM

.LALL : List all - including the leading period. .SALL : suppress all - not list any source code of a macro expansion .XALL : default - list only the instructions that generate object code. Macro Listing directive

The LOCAL directive Used for define the data items and instruction labels within the macro definition itself. LOCALdummy-1, dummy-2,.. ;One or more dummy argument

Including Macros from a library Programs can use any of the cataloged macros by use an INCLUDE directive like this. INCLUDEPath and file name Example:INCLUDEF:\MACRO.LBY

The PURGE directive Use to delete the unwanted macros from the current assembly. PURGEMacro names Example:PURGEPROMPT, DIVIDE

Concatenation Used the ampersand (&) character tells the assembler to join text or symbols. STRMOVEMACROTAG REPMOVS&TAG ENDM

 REPT : Repeat Directive  IRP : Indefinite Repeat Directive  IRPC : Indefinite Repeat Character Directive Repetition directive

Repeat a block of statements up to ENDM according to the number of times in the expression entry. REPTexpression Repetition directive : REPT

REPT4 DECSI ENDM REPT : Examples

N = 0 REPT5 N = N + 1 DBN ENDM REPT : Examples

Repeat a block of instructions up to ENDM. IRPdummy, Repetition directive : IRP

IRPN, DBN ENDM IRP : Examples

IRPREG, PUSHREG ENDM IRP : Examples

Repeat a block of statements up to ENDM. IRPCdummy, string Repetition directive : IRPC

IRPCN, DWN ENDM IRPC : Examples

IFxx(condition)... ELSE(optional)... ENDIF(end of IF) Conditional directives

 IF : If the expression evaluates to a nonzero value, assemble the statements within the conditional block.  IFE : If the expression evaluates to a zero, assemble the statements within the conditional block.

Conditional directives  IF1 (no expression) : If processing pass 1, act on the statements in the conditional block.  IF2 (no expression) : If processing pass 2, act on the statements in the conditional block.

Conditional directives  IFDEF symbol : If the symbol is defined in the program or is declared as EXTRN, process the statements in the conditional block.  IFNDEF symbol : If the symbol is not defined or is not declared as EXTRN, process the statements in the conditional block.

Conditional directives  IFB : If the argument is blank, process the statements in the conditional block. The argument requires angle brackets.  IFNB : If the argument is not blank, process the statements in the conditional block. The argument requires angle brackets.

Conditional directives  IFIDN, : If the argument-1 string is identical to the argument-2 string, process the statements in the conditional block. The argument require angle brackets.

Conditional directives  IFDIF, : If the argument-1 string is different to the argument-2 string, process the statements in the conditional block. The argument require angle brackets.

Conditional directives  IF and IFE can use the relational operators : –EQ (equal) –NE (not equal) –LT (less than) –LE (less than or equal) –GT (greater than) –GE (greater than or equal)

FINISHMACRORETCODE MOVAH, 3CH IFNB MOVAL, RETCODE ENDIF INT21H ENDM Examples

INT21MACROFUNCTION, DXADDRES MOVAH, FUNCTN IFNB MOVDX, OFFSET DXADDRES ENDIF INT21H ENDM Examples

IFxx[condition]...(invalid condition) EXITM... ENDIF EXITM directives

IFCNTR ; Macro expansion terminated EXITM ENDIF Using IF and IFDEF conditions

IFIDN, REPMOVSB... Using IFIDN condition

IFIDN, REPMOVSW... Using IFIDN condition