Call system

In Data-processing, a call system is a function provided by the core of a Operating system and used by the programs being carried out in the Espace user (in other words, all programs distinct from the core).

The role of the core is to manage the material resources (it contains pilots of peripherals) and to provide to the programs a uniform interface for the access to these resources.

Some calls traditional systems:

open , read , Write and closed which allows handling on the filesystems,
alloc , free to allocate and désallouer memory.

On the majority of the operating systems, the calls system can be used like simple functions written in C.

On the majority of the cores (in particular monolithic cores as the Core Linux) the calls systems are implemented by an instruction machine (interupt, supervisor cal,…) who makes rock the processor in the core in supervisory mode (while having suitably passed the parameters of the call system, for example in the registers). In this respect, the call system is distinct from a call of function, and the process which carries out it automatically the fact. Seen applicatif program, a call system is atomic (it was carried out - possibly in error or not).

An operating system as Linux has more than 200 calls distinct systems (of which some recut or offer similar functionalities: read , pread , even mmap and recv ).

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