INFO: Negative Values Use Two's Complement

• The Microsoft C/C++ Compiler (CL.EXE) included with: - Microsoft C for MS-DOS, versions 6.0, 6.0a, 6.0ax - Microsoft C for OS/2, versions 6.0, 6.0a - Microsoft C/C++ for MS-DOS, version 7.0 - Microsoft Visual C++ for Windows, versions 1.0, 1.5 - Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 4.0, 5.0

SUMMARY

In most C compilers, including the Microsoft C Compiler, negative values are represented internally in two's complement format. Two's complement can be obtained by negating each bit of the value, then adding 1. Performing two's complement twice generates the original value.

The following is an example:

   Original Value               Two's Complement
   --------------               ----------------

   (dec)   (hex)  (binary)      (dec)   (hex)   (binary)
   127     0x7f   01111111      -127    0x81    10000001
   111     0x6f   01101111      -111    0x91    10010001
  -111     0x91   10010001       111    0x6f    01101111