UNIX

Recently, the X/Open Company Limited, an independent, open systems organization supported by the world's largest information system suppliers, user organizations, and software companies, has defined a Single UNIX Specification that all platforms can support in order to assure portability of applications in multi-vendor systems.

A highly portable operating system originally developed by Bell Laboratories that features multiprogramming in a multiuser environment. UNIX is implemented in the C language. UNIX was originally developed for use on minicomputers but has been adapted on mainframes and microcomputers. It is especially suitable for multiprocessor, graphics, and vector-processing systems. Many of the commands in the OpenExtensions shell are based on similar commands available with UNIX System V.

OpenExtensions for z/VM conforms to the IEEE Std 1003.1-1990 and ISO/IEC 9945-1:1990(E), hereafter referred to as POSIX.1, except that OpenExtensions for z/VM does not fully support the fork() function. There is a very limited fork() function available which has severe use restrictions. Refer to the C for VM/ESA: Library Reference , SC23-3908 for information on these restrictions.

The OpenExtensions for z/VM implemenation supports the POSIX.1 standard and the FIPS 151-1 restrictions on that standard.