... even know there is others. Systems services are the real interface to the Operating system, these services are used to describe the set of functions provided by an Operating system to allow a user to request services from it. Each Operating system has its own set of system services that made programs which used such system services to difficult to port another system, POSIX, the pos stands for portable Operating system. POSIX is not an Operating system but is a standard for Operating system designers. The POSIX interface is available on almost all Operating system, such as UNIX, WINDOWS NT, OS/2 and open VMS. The POSIX programming interface is simple system services are descried fully in the manuals supplied with each Operating system. All of the system services are defined as C functions that mean that they return a value, this value is not just discarded. System programming is different from application programming, where it can ...

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