PROCEDURE TO COLLECT MULTIPLE DIGITS AS INPUT IN 8086 ASM

;PROCEDURE TO COLLECT MULTIPLE DIGITS AS INPUT IN 8086 ASSEMBLY
;AUTHOR: ANUEBUNWA VICTOR O.
;ASSEMBLER: MASM611

.MODEL SMALL
.STACK
.CODE
value DB 0000H
e1 DB "Wrong input",'$'
e2 DB 'No value entered',0AH,0DH,'Program exiting...','$'

.CODE
START:
MOV AX, @data
MOV DS, AX
;YOUR CODES GOES HERE
MOV AH, 4CH
INT 21H

;You may avoid using PUSHA and POPA if it gives error during assembling but be sure to backup needed ;values in AX,BX,CX and DX before calling this procedure.

;Beginning of procedure
read            proc
                PUSHA                   ;Push current values in register to stack
                MOV AX, 0000H       ;
                MOV CX, 0000H       ;
                MOV BX, 0000H       ;
                MOV DX, 0000H       ;Clears register AX,BX,CX and DX
.tryloop1:              MOV AH, 01H
                INT 21H             ;Calls DOS funtion to receive a character
                JMP check           ;Jumps to check character recieved
continue_loop:                  ;Where loop continues assuming character passes check
                MOV BX, 0000H       ;Clears BX again
                MOV BL, AL          ;Moves AL to BL
                SUB BX, 30H         ;Subtracts 30H to get the actual value of character
                PUSH BX         ;Push BX to stack
                INC CX              ;Increments CX to track the lenght of the value
                CMP AL, 0DH     ;Checks if character was carriage return
                JNE .tryloop1           ;Jumps if not carrige return

                CMP CX, 1           ;Checks if no value was entered
                JE error_msg2           ;jumps if no value was entered
                POP AX          ;Pops out last value in stack(carrige return)
                dec CX              ;Decrements counter

                MOV BX, 1           ;initialize multiplier
.tryloop2:              MOV AX, 0000H       ;Clears AX
                POP AX              ;Pops data to AX
                MUL BX              ;Multiplies AX by BX
                ADD value, AX       ;Add AX to value

                XCHG AX, BX     ;Exchanges AX and BX
                MOV BX, 10          ;Moves 10 into BX
                MUL BX              ;Multiplies AX by BX(containing 10)
                XCHG AX, BX     ;Exchanges back AX and BX
                dec CX              ;Decrements counter
                JNE .tryloop2           ;Repeats until CX equals zero

                MOV AH, 02H
                MOV DL, 0aH
                INT 21H             ;Prints line-feed
                POPA              ;Pops values of register before procedure call from stack
                RET                 ;returns control
read        endp                                             ;End of procedure.

check:          CMP AL, 0DH     ;Checks if the character is carriage return
                JE continue_loop        ;Jumps back into loop if carriage return
                CMP AL, '0'         ;Checks if a non-digit was entered
                JNGE error_msg
                CMP AL, '9'
                JNLE error_msg      ;Displays error if a non-digit was entered
                JMP continue_loop       ;Else it jumps back into loop

error_msg:      MOV AH, 02H
                MOV DL, 0AH
                INT 21H             ;Prints line-feed
                LEA DX, e1
                MOV AH, 09H
                INT 21H             ;Prints string
                JMP start ;Restarts program(assuming you have Start: as your starting label)
END START