TITLE   Parameter passing via registers      PROCEX1.ASM
COMMENT |
        Objective: To show parameter passing via registers
            Input: Requests two integers from the user.
|          Output: Outputs the sum of the input integers.
.MODEL SMALL
.STACK 100H
.DATA
prompt_msg1  DB   'Please input the first number: ',0
prompt_msg2  DB   'Please input the second number: ',0
sum_msg      DB   'The sum is ',0

.CODE
INCLUDE io.mac

main  PROC
      .STARTUP
      PutStr  prompt_msg1    ; request first number
      GetInt  CX             ; CX := first number
      nwln
      PutStr  prompt_msg2    ; request second number
      GetInt  DX             ; DX := second number
      nwln
      call    sum            ; returns sum in AX
      PutStr  sum_msg        ; display sum
      PutInt  AX
      nwln
done:
      .EXIT
main  ENDP

;-----------------------------------------------------------
;Procedure sum receives two integers in CX and DX.
; The sum of the two integers is returned in AX.
;-----------------------------------------------------------
sum   PROC
      mov     AX,CX          ; sum := first number
      add     AX,DX          ; sum := sum + second number
      ret
sum   ENDP
      END     main