Lab 2

; SP, ASM, Lab 2, made by Katolikian Tihran, IK-62
; input 2 byte integer; then output 2 byte integer
; Data segment byte arrays:
    ; "Buffer" - buffer for inputing integer with max size on highest position;
    ; "Msg_error" - string line with message about any error;
    ; "Msg_enterNum" - message which suggest user to input the integer;
    ; "Msg_pressKey" - message which suggest user to press any key to finish the program;
; Interrupts (explanation of interrupts used in this program):
    ; "int 21h {ah = 0ah, ds:dx - input buffer adress}" - buffered input;
    ; "int 21h {ah = 02h, dl = symbol to output}" - output symbol from dl;
    ; "int 21h {ah = 9, dx = str ptr}" - output the string from adress from dx;
    ; "int 16h {ah = 10h}" - read expanded keyboard character
    ; "int 21h {ah = 4ch}" - end program.


;data segment
DSEG segment
    Buffer DB 7, '?', 6 dup('?'), '$'
    Msg_error DB 'Error.$'
    Msg_enterNum DB 'Please, enter a number: $'
    Msg_pressKey DB 'Press any key to show number...', 0Dh, 0Ah, '$'
DSEG ends

;code segment
CSEG segment
    assume ds:DSEG, cs:CSEG
    Start:
    mov ax, DSEG
    mov ds, ax

    lea dx, Msg_enterNum
    mov ah, 9
    int 21h

    call Get_integer
    cmp di,2
    jz er

    cmp byte ptr [Buffer + 1], 0    ;if no input
    je er
    cmp byte ptr [Buffer + 1], 1
    je Only_sign

    jmp Output

    Only_sign:
    cmp byte ptr [Buffer + 2], '+'
    je er
    cmp byte ptr [Buffer + 2], '-'
    je er

    Output:

    push ax
    lea dx, Msg_pressKey
    mov ah, 9
    int 21h
    mov ah, 10h
    int 16h
    pop ax

    call Print_integer
    mov ah, 10h
    int 16h
    mov ah, 4Ch
    int 21h

    er:
    lea dx, Msg_error
    mov ah,09
    int 21h
    mov ah, 10h
    int 16h
    mov ah, 4ch
    int 21h

    ;proc gets integer in the Buffer
Get_integer proc

    mov ah,0ah
    xor di,di
    mov dx,offset Buffer
    int 21h     ;buff input
    mov dl,0ah  ;symbol to output
    mov ah,02
    int 21h     ;endl

    mov di,0
    lea si, Buffer + 2  ;to the first symbol
    cmp byte ptr [si],"+"
    je p1
    cmp byte ptr [si],"-"
    jne p2
    mov di,1
    p1:
    inc si
    p2:
    xor ax,ax
    mov bx,10
    p3:
    mov cl,[si]
    cmp cl,0dh
    jz endin    ;if it's end of the number, then end input


    cmp cl,'0'
    jb erg      ;less than 0
    cmp cl,'9'
    ja erg      ;more then 9

    sub cl,'0'  ;symbol to number variable
    mul bx
    jc erg      ;if we have overflow
    add ax,cx
    ;jc erg
    cmp ax, 8000h
    ja erg
    inc si
    jmp p3

    erg:
    mov di,2
    ret

    endin:
    cmp ax,0
    je newEnd
    cmp di,1
    je p4
    and ax,7fffh    ;for 32768
    cmp ax,0
    je erg
    newEnd:
    ret

    p4:
    neg ax
    ret
Get_integer endp

Print_integer proc

    mov bx, ax
    or bx, bx  ;!
    jns no_minus
    mov al, '-'
    int 29h
    neg bx
    no_minus:
    mov ax,bx
    xor cx,cx
    mov bx,10
    m2:
    xor dx,dx
    div bx
    add dl,'0'
    push dx
    inc cx
    test ax,ax
    jnz m2
    m3:
    pop ax
    int 29h
    loop m3
    ret

Print_integer endp

CSEG ends
END Start