ReadInt PROC

   Reads a 32-bit signed decimal integer from standard input, stopping when the Enter key is pressed.
   All valid digits occurring before a non-numeric character are converted to the integer value.
   Leading spaces are ignored, and an optional leading + or - sign is permitted.
   ReadInt will display an error message, set the Overflow flag, and reset EAX to zero if the value entered cannot be represented as a 32-bit signed integer.

Call args:   None

Return args: If OF=0, EAX = valid binary value, and SF=sign.
             If OF=1, EAX = 0 (invalid input)

Example:

.data
intNum    DWORD ?
promptBad BYTE "Invalid input, please enter again",0

.code
read:  call ReadInt
       jno  goodInput

       mov  edx,OFFSET promptBad
       call WriteString
       jmp  read        ;go input again

goodInput:
       mov  intNum,eax  ;store good value