Process Exit Values Must Lie Between 0 and 255 Inclusive

MS-DOS                 | OS/2       | WINDOWS

The information in this article applies to:

• Microsoft C for MS-DOS, versions 6.0, 6.0a, and 6.0ax
• Microsoft C for OS/2, versions 6.0, and 6.0a
• Microsoft C/C++ for MS-DOS, version 7.0
• Microsoft Visual C++ for Windows, versions 1.0 and 1.5

Exit values must range between 0 and 255 inclusive. This limitation has its roots in the "terminate with return code" interrupt function (Interrupt 21H, function 4CH). Using this function, exit values are specified in the AL register. The AL register allows values from 0 to 255. All Microsoft C programs under MS-DOS terminate using this function.

Under OS/2, the same limitation exists. Although OS/2 does not use interrupts as MS-DOS does, the reasoning is analogous.

Exit values can be tested using the functions spawnl(), spawnle(), spawnlp(), spawnlpe(), spawnv(), spawnve(), spawnvp(), and spawnvpe(). Also, batch files may test exit values using the IF ERRORLEVEL statement.