Ensamblador - Suma DOS NÚMEROS

Esto es para el emulador 8086 este programa toma 2 numeros del usuario, y calcula
la suma luego muestra la salida por pantalla.
---------------------- cortar aca -----------------------

; this sample gets two numbers from the user,
; then it calculates the sum of these numbers,
; and prints it out.

name "calc"

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; these maros are copied from emu8086.inc ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; this macro prints a string that is given as a parameter, example:
; PRINTN 'hello world!'
; the same as PRINT, but new line is automatically added.
PRINTN MACRO sdat
LOCAL next_char, s_dcl, printed, skip_dcl

PUSH AX ; store registers...
PUSH SI ;

JMP skip_dcl ; skip declaration.
s_dcl DB sdat, 0Dh,0Ah, 0

skip_dcl:
LEA SI, s_dcl

next_char:
MOV AL, CS:[SI]
CMP AL, 0
JZ printed
INC SI
MOV AH, 0Eh ; teletype function.
INT 10h
JMP next_char
printed:

POP SI ; re-store registers...
POP AX ;
ENDM

; this macro prints a char in AL and advances
; the current cursor position:
PUTC MACRO char
PUSH AX
MOV AL, char
MOV AH, 0Eh
INT 10h
POP AX
ENDM
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


org 100h




jmp start ; skip data.

msg1 db 0Dh,0Ah, 'input numbers in this range: [-32768..32767]', 0Dh,0Ah
db 0Dh,0Ah, 'enter first number: $'

msg2 db 0Dh,0Ah, 'enter second number: $'

msg3 db 0Dh,0Ah, 'the sum is: $'

; declaration of variable:
num dw ?

start:

; print first message
mov dx, offset msg1
mov ah, 9
int 21h

call scan_num

; keep first number:
mov num, cx

; print second message
mov dx, offset msg2
mov ah, 9
int 21h

call scan_num

; add numbers:
add num, cx
jo overflow

; print the result:
mov dx, offset msg3
mov ah, 9
int 21h

mov ax, num
call print_num

jmp exit

; process overlow error:
overflow:

printn 'we have overflow!'

exit:

; wait for any key press:
mov ah, 0
int 16h

ret ; return control to operating system.



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; these functions are copied from emu8086.inc ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; gets the multi-digit SIGNED number from the keyboard,
; and stores the result in CX register:
SCAN_NUM PROC NEAR
PUSH DX
PUSH AX
PUSH SI

MOV CX, 0

; reset flag:
MOV CS:make_minus, 0

next_digit:

; get char from keyboard
; into AL:
MOV AH, 00h
INT 16h
; and print it:
MOV AH, 0Eh
INT 10h

; check for MINUS:
CMP AL, '-'
JE set_minus

; check for ENTER key:
CMP AL, 0Dh ; carriage return?
JNE not_cr
JMP stop_input
not_cr:

CMP AL, 8 ; 'BACKSPACE' pressed?
JNE backspace_checked
MOV DX, 0 ; remove last digit by
MOV AX, CX ; division:
DIV CS:ten ; AX = DX:AX / 10 (DX-rem).
MOV CX, AX
PUTC ' ' ; clear position.
PUTC 8 ; backspace again.
JMP next_digit
backspace_checked:

; allow only digits:
CMP AL, '0'
JAE ok_AE_0
JMP remove_not_digit
ok_AE_0:
CMP AL, '9'
JBE ok_digit
remove_not_digit:
PUTC 8 ; backspace.
PUTC ' ' ; clear last entered not digit.
PUTC 8 ; backspace again.
JMP next_digit ; wait for next input.
ok_digit:

; multiply CX by 10 (first time the result is zero)
PUSH AX
MOV AX, CX
MUL CS:ten ; DX:AX = AX*10
MOV CX, AX
POP AX

; check if the number is too big
; (result should be 16 bits)
CMP DX, 0
JNE too_big

; convert from ASCII code:
SUB AL, 30h

; add AL to CX:
MOV AH, 0
MOV DX, CX ; backup, in case the result will be too big.
ADD CX, AX
JC too_big2 ; jump if the number is too big.

JMP next_digit

set_minus:
MOV CS:make_minus, 1
JMP next_digit

too_big2:
MOV CX, DX ; restore the backuped value before add.
MOV DX, 0 ; DX was zero before backup!
too_big:
MOV AX, CX
DIV CS:ten ; reverse last DX:AX = AX*10, make AX = DX:AX / 10
MOV CX, AX
PUTC 8 ; backspace.
PUTC ' ' ; clear last entered digit.
PUTC 8 ; backspace again.
JMP next_digit ; wait for Enter/Backspace.


stop_input:
; check flag:
CMP CS:make_minus, 0
JE not_minus
NEG CX
not_minus:

POP SI
POP AX
POP DX
RET
make_minus DB ? ; used as a flag.
SCAN_NUM ENDP



; this procedure prints number in AX,
; used with PRINT_NUM_UNS to print signed numbers:
PRINT_NUM PROC NEAR
PUSH DX
PUSH AX

CMP AX, 0
JNZ not_zero

PUTC '0'
JMP printed

not_zero:
; the check SIGN of AX,
; make absolute if it's negative:
CMP AX, 0
JNS positive
NEG AX

PUTC '-'

positive:
CALL PRINT_NUM_UNS
printed:
POP AX
POP DX
RET
PRINT_NUM ENDP


; this procedure prints out an unsigned
; number in AX (not just a single digit)
; allowed values are from 0 to 65535 (FFFF)
PRINT_NUM_UNS PROC NEAR
PUSH AX
PUSH BX
PUSH CX
PUSH DX

; flag to prevent printing zeros before number:
MOV CX, 1

; (result of "/ 10000" is always less or equal to 9).
MOV BX, 10000 ; 2710h - divider.

; AX is zero?
CMP AX, 0
JZ print_zero

begin_print:

; check divider (if zero go to end_print):
CMP BX,0
JZ end_print

; avoid printing zeros before number:
CMP CX, 0
JE calc
; if AX<BX then result of DIV will be zero:
CMP AX, BX
JB skip
calc:
MOV CX, 0 ; set flag.

MOV DX, 0
DIV BX ; AX = DX:AX / BX (DX=remainder).

; print last digit
; AH is always ZERO, so it's ignored
ADD AL, 30h ; convert to ASCII code.
PUTC AL

MOV AX, DX ; get remainder from last div.

skip:
; calculate BX=BX/10
PUSH AX
MOV DX, 0
MOV AX, BX
DIV CS:ten ; AX = DX:AX / 10 (DX=remainder).
MOV BX, AX
POP AX

JMP begin_print

print_zero:
PUTC '0'

end_print:

POP DX
POP CX
POP BX
POP AX
RET
PRINT_NUM_UNS ENDP


ten DW 10 ; used as multiplier/divider by SCAN_NUM & PRINT_NUM_UNS.