9. The atod Macro (ASCII to DWORD)

• The atod converts an ASCII string at source to 32-bit signed integer number:

  • atod source

  where source is a null-terminated string in the following format:

  • optional leading blanks (space characters, ASCII codes 20h)

  • optional + or - sign, followed by

  • digits

• The resulting 2's complement number is put in EAX:

      .DATA           ; Begin initialized data segment
          buffer      BYTE    12 DUP (?)
          ..
      .CODE           ; Code segment
          ..
          input   buffer, 12 ; Read zero to 10 ASCII characters
          atod    buffer     ; Convert string to 2's complement number
          jno     @F         ; Check the overflow flag
          ; Handle input error:
          ..
      @@:
          ; Success: result of conversion is in EAX
          ..