I need to prompt to user a msg that tells him to write a number , then I store this number and do some operation on it After searching in INT 21h I found this :
INT 21h / AH=1 - read character from standard input, with echo, result is stored in AL.
if there is no character in the keyboard buffer, the function waits until any key is pressed.
example:
mov ah, 1
int 21h
The main problem that this only reads one character and represent it as ASCII so If I need to write the number "357" I will read it as 3 , 5 , 7
and this is not my goal . any ideas ?
When you managed to get the user input, put the its pointer in ESI (ESI = address to the string)
.DATA
myNumber BYTE "12345",0 ;for test purpose I declare a string '12345'
Main Proc
xor ebx,ebx ;EBX = 0
mov esi,offset myNumber ;ESI points to '12345'
loopme:
lodsb ;load the first byte pointed by ESI in al
cmp al,'0' ;check if it's an ascii number [0-9]
jb noascii ;not ascii, exit
cmp al,'9' ;check the if it's an ascii number [0-9]
ja noascii ;not ascii, exit
sub al,30h ;ascii '0' = 30h, ascii '1' = 31h ...etc.
cbw ;byte to word
cwd ;word to dword
push eax
mov eax,ebx ;EBX will contain '12345' in hexadecimal
mov ecx,10
mul ecx ;AX=AX*10
mov ebx,eax
pop eax
add ebx,eax
jmp loopme ;continue until ESI points to a non-ascii [0-9] character
noascii:
ret ;EBX = 0x00003039 = 12345
Main EndP