macros
DESCRIPTION
MACROS. Suthida Chaichomchuen [email protected]. 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. - PowerPoint PPT PresentationTRANSCRIPT
PurposesTo 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 operationString-handling routines
Format of macro definition
macronameMACRO [parameter list][instructions]ENDM
;Define macro;Body of macro;End of macro
Simple macro definitions
INITZ MACRO ;Define macroMOV AX,@data ; BodyMOV DS,AX ; ofMOV ES,AX ; macro definitionENDM ;End of macro
Simple macro definitions
FINISH MACRO ;Define macroMOV AX,4C00H ;Body ofINT 21H ;macro definitionENDM ;End of macro
Using parameter in Macros
PROMPT MACRO MESSAGE;dummy argumentMOV AH,09HLEA DX,MESSAGEINT 21HENDM ;End of macro
Using parameter in Macros
2MESSAGE DB ‘Enter the date as mm/dd/yy’
PROMPT 2
Macro Comments
PROMPT MACRO MESSAGE; This macro permits a display of messages
MOV AH,09H ;Request displayLEA DX,MESSAGE ;promptINT 21HENDM
.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.
LOCAL dummy-1, dummy-2, . . ;One or more dummy argument
Including Macros from a library
Programs can use any of the cataloged macros by usean INCLUDE directive like this.
INCLUDE Path and file name
Example: INCLUDE F:\MACRO.LBY
The PURGE directive
Use to delete the unwanted macros from the currentassembly.
PURGE Macro names
Example: PURGE PROMPT, DIVIDE
Concatenation
Used the ampersand (&) character tells the assembler to join text or symbols.
STRMOVE MACRO TAGREP MOVS&TAGENDM
REPT : Repeat DirectiveIRP : 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.
REPT expression
Repetition directive : REPT
REPT 4DEC SI
EEEE
REPT : Examples
N = 0REPT 5
N = N + 1DB N
EEEE
REPT : Examples
Repeat a block of instructions up to ENDM.
IRP dummy, <argument>
Repetition directive : IRP
IRP N, <3, 9, 17, 25, 28>DB N
ENDM
IRP : Examples
IRP REG, <AX, BX, CX, DX>PUSH REG
ENDM
IRP : Examples
Repeat a block of statements up to ENDM.
IRPC dummy, string
Repetition directive : IRPC
IRPC N, 345678DW N
ENDM
IRPC : Examples
IFxx (condition) . . .
EEEE (optional) . . .
ENDIF (end of IF)
Conditional directives
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 <argument> : If the argument is blank, process the statements in the conditional block. The argument requires angle brackets.
IFNB <argument> : If the argument is not blank, process the statements in the conditional block. The argument requires angle brackets.
Conditional directives
- - 1 2IFIDN <arg >,<arg > : EEE EEEEE EEE-E EEEEEE EE E1
- 2dentical to the argument string, processthest at ement s i n t he condi EEEEEE EEE EEEEEEEE EEEEEEE EE. glebr acket s.
Conditional directives
- - 1 2IFDIF <arg >,<arg > : I - 1f the argument string is d
- 2ifferent to the argument string, processthest at ement s i n t he condi tionalblock. The ar gument r equi r e an glebr acket s.
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)
FINISH MACRO RETCODEMOV AH, 3CHIFNB <RETCODE>
MOV AL, RETCODEENDIFINT 21HENDM
Examples
INT21 MACRO FUNCTION, DXADDRESMOV AH, FUNCTNIFNB <DXADDRES>
MOV DX, OFFSET DXADDRESENDIFINT 21HENDM
Examples
IFxx [condition] . . . (invalid condition)
EEEEE . . .
ENDIF
EXITM directives
IF CNTR ; Macro expansion terminated
EXITMENDIF
Using IF and IFDEF conditions
IFIDN <&TAG>,<B>REP MOVSB. . .
Using IFIDN condition
IFIDN <&TAG>,<W>REP MOVSW. . .
Using IFIDN condition