Header File 

dos.h 

Syntax 

extern unsigned char _osminor; 

Description 

The minor version number of the operating system is available individually through _osminor. For example, if you are running DOS version 3.2, _osminor will be 20. 

This variables can be useful when you want to write modules that will run on DOS versions 2.x and 3.x. Some library routines behave differently depending on the DOS version number, while others only work under DOS 3.x and higher. For example, refer to creatnew and _rtl_open.