process.h is a C header file which contains function declarations and macros used in working with threads and processes. Neither the header file nor the functions are defined by either the ANSI/ISO C standard or by POSIX. Most C compilers that target DOS, Windows 3.1x, Win32, OS/2, Novell NetWare or DOS extenders supply this header and the library functions in their C library.
The first reference to the file was in a post on the net.micro.pc usenet and dates back to Oct-26-1986. The compiler used by the user was Microsoft C compiler Version 3.0. The Lattice C compiler version 3.30 (Aug-24-1988) did not have such a header file, but offered similar functions. As of Borland, they provided it in their Turbo C compiler version 2.01. The C Ware-Personal C compiler version 1.2c (June 1989) had only the ANSI headers.It is a very important tool in c language.