LEN     EQU    80
DOSSEG
.MODEL SMALL
 
.STACK 100h
 
.DATA
	Prompt1 DB  "Input a string:  ", 0
 	Prompt2 DB  "Do another?  ", 0
 	String  DB  (LEN + 1) dup(?)
.CODE
 	EXTRN getStr:NEAR, putStr:NEAR, newLine:NEAR
;----------------------------------------------------------------
Start:
 	mov   ax, @DATA
 	mov   ds, ax
Begin:
 	mov   ax, OFFSET Prompt1
 	push  ax
 	call  putStr
 	call  newLine
 	call  newLine
       
 	mov   ax, OFFSET String
 	push  ax
 	call  getStr
 	call  newLine
 	call  newLine
   
        mov   ax, OFFSET String
        push  ax
        call  putStr
        call  newLine
        call  newLine

        mov   ax, OFFSET Prompt2
        push  ax
        call  PutStr

        mov   ax, OFFSET String
        push  ax
        call  getStr

        call  newLine
        call  newLine

        mov   bx, OFFSET String
        cmp   BYTE PTR [bx], 'y'
        je    Begin

 	mov   ax, 4c00h
 	int   21h
END Start

MACROS:
Look at code in prog5_4.asm (above)

	mov	ax, OFFSET Prompt1
	push	ax
	call	putStr

is repreated (with variations) several times in the program

MACROS allow us to avoid this kind of mindless repetition

Broadly speaking:
MACROS:   simply substitute one piece of text with another

syntax:

macroName	MACRO	ListOfReplaceableParameters

	...
	macro code
	...

ENDM

MACRO is a reserved word
ENDM  end of macro definition



To invoke a macro named Macro1, just use:

	Macro1	listofArguments

MASM replaces this line by a copy of the macro code.
Each occurence of a replaceable parameter replaced by the
corresponding argument


Consider simple MACRO definition

inpStr	MACRO	Buffer

	push	ax
	mov	ax, OFFSET Buffer
	push	ax
	call	getStr
	pop	ax
ENDM

Makes the call to getStr easier

To invoke this macro:

	inpStr	String

MASM replaces this invocation by

	push	ax
	mov	ax, OFFSET String
	push	ax
	call	getStr
	pop	ax


Here's another macro for calling putStr

outStr	MACRO	Buffer
	
	push  ax
 	mov   ax, OFFSET Prompt1
 	push  ax
 	call  putStr
	pop   ax

ENDM
Let's rewrite program prog5_4.asm using these macros:

       LEN     EQU    80
DOSSEG
.MODEL SMALL
 
.STACK 100h
 
.DATA
	Prompt1 DB  "Input a string:  ", 0
 	Prompt2 DB  "Do another?  ", 0
 	String  DB  (LEN + 1) dup(?)
.CODE
 	EXTRN getStr:NEAR, putStr:NEAR, newLine:NEAR
;----------------------------------------------------------------
Start:
 	mov   ax, @DATA
 	mov   ds, ax
Begin:

	outStr	Prompt1
 	call  newLine
 	call  newLine
       
	inpStr	String
 	call  newLine
 	call  newLine
   
	outStr	String
        call  newLine
        call  newLine

	outStr	Prompt2

	inpStr	String

        call  newLine
        call  newLine

        mov   bx, OFFSET String
        cmp   BYTE PTR [bx], 'y'
        je    Begin

 	mov   ax, 4c00h
 	int   21h
END Start


Well we know how to define a macro
     we know how to invoke a macro

Where do we put macro definitions?

We usually gather related sets of macros and
put them in an include file.

Here's how I would (partially) solve your assignment


TITLE AS6.asm  

INCLUDE         as6.mac	; Contains the macro
			; definition of strLeng
 
LEN     EQU    80

DOSSEG
.MODEL SMALL
 
.STACK 100h
 
.DATA
	Prompt1 DB  "Input a string:  ", 0
	Prompt2 DB  "Do another?  ", 0
	String  DB  (LEN + 1) dup(?)
.CODE
       EXTRN getStr:NEAR, putStr:NEAR, newLine:NEAR, DECOUT:NEAR
;----------------------------------------------------------------
Start:
	mov   ax, @DATA
	mov   ds, ax
Begin:
	mov   ax, OFFSET Prompt1 ; shd replace with macro 
	push  ax		 ; invocation
	call  putStr
	call  newLine
	call  newLine
       
	mov   ax, OFFSET String  ; should also replace with
	push  ax                 ; macro invocation
	call  getStr
	call  newLine
	call  newLine
   
	strLeng String	; Invoking macro strLeng

	mov     dx, ax	; outputing string's  length
	CALL    DECOUT
	call    newLine
   
	mov   ax, 4c00h ; exiting
	int   21h
END Start

The file as6.mac would look like

;---------------------------------------------------------------
COMMENT     #   MACRO HEADER    
NAME:           strLeng         FILE:as6.mac    
PURPOSE:        finds length of asciiz string
CALLED AS:      strLeng Buffer
		where Buffer is a storage area for the
		string. Buffer must be in the segment pointed
		to by ds
REMARKS:      Buffer must be long enough to hold input string
	    #   and null-terminator

strLeng MACRO String

	code...

ENDM
;----------------------------------------------------------------

Debugging code with macros is more difficult.
Look out.