Assembly_Simplified_Literally/PP_Q3_P1.asm at main · sys-deamon/Assembly_Simplified_Literally · GitHub

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; Hook interrupt 65 with following services
; Take two BCD numbers
; Calc Sum
; Display Sum

.model small
.stack 100h
.data

result dw 0
msg db "The Result is:$"

.code

mov ax, @data
mov ds, ax

mov ax, 0
mov es, ax

mov bx, 4 * 65h

mov word ptr es:[bx], offset interrupt_handler
mov word ptr es:[bx + 2], seg interrupt_handler

int 65h

mov ax, 4ch
int 21h

interrupt_handler proc

    ; Read first digit
    mov ah, 01h
    int 21h

    sub al, '0'
    shl al, 4

    mov dh, al

    ; Read second digit
    mov ah, 01h
    int 21h

    sub al, '0'

    or dh, al

    ; Read third digit
    mov ah, 01h
    int 21h

    sub al, '0'
    shl al, 4

    mov dl, al

    ; Read fourth digit
    mov ah, 01h
    int 21h

    sub al, '0'

    or dl, al

            ; FOR SECOND DIGIT

    ; Read first digit
    mov ah, 01h
    int 21h

    sub al, '0'
    shl al, 4

    mov ch, al

    ; Read second digit
    mov ah, 01h
    int 21h

    sub al, '0'

    or ch, al

    ; Read third digit
    mov ah, 01h
    int 21h

    sub al, '0'
    shl al, 4

    mov cl, al

    ; Read fourth digit
    mov ah, 01h
    int 21h

    sub al, '0'

    or cl, al

                ; ADDING

    add dx, cx
    mov [result], dx

                ; DISPLAYING
    ; Message
    mov dx, offset msg
    mov ah, 09h
    int 21h

    ; Result

    ; initialize video memory
    mov ax, 0xb800
    mov es, ax

    ;load the result
    mov dx, [result]

    ;DISPLAYING THE FIRST DIGIT

    ;load the result again
    mov ax, dx

    ;isolate the first digit
    shr ax, 12

    ;display it
    mov di, 2*(0*80+22)
    call Display

    ; DISPLAYING THE SECOND DIGIT

    ;load the result again
    mov ax, dx

    ;isolate the second digit
    shl ax, 4
    shr ax, 12

    ;display
    inc di
    call Display

    ; DISPLAYING THIRD DIGIT

    ;load the variable again
    mov ax, dx

    ;isolate the third digit
    shl ax, 8
    shr ax, 12

    ;display it
    inc di
    call Display

    ; DISPLAYING FOURTH DIGIT

    ;load the result again
    mov ax, dx

    ;isolate the fourth digit
    shl ax, 12
    shr ax, 12

    ;display it
    inc di
    call Display

    ret

interrupt_handler endp


Display proc

    ; ensure there is only last 4 bits
    and ax, 0Fh

    ; check if its a number or letter

    cmp al, 9

    ;if greater
    jg its_letter

    ;otherwise its a number
    add al, '0'

    ;proceed to display
    jmp display_it

its_letter:

add al, 'A' - 10

display_it:

    ;display the character
    mov es:[di], al
    inc di
    mov es:[di], 11100100b

    ret
 Display endp