Services vs Directives vs System Calls

[Joel Sherrill]

ricardo wrote:
> Hi,
>
>
> In the RTEMS POSIX API User's Guide for RTEMS 4.6.6 the API functions
> are separated in three groups (services, directives or system calls).
> Some managers have services (like mutex manager), others have directives
> (like semaphore manager) and only one has system calls (timer manager)
>
>
>   
Human inconsistency on the authors part and inconsistency
between various standards.
> In RTEMS C User’s Guide (for classical api), we only find directives
> under each manager.
>   
The RTEID/ORKID standard the Classic API is based upon
uniformly used the word service.

POSIX sometimes refers to them as functions. Sometimes
as APIs.  Sometimes as interfaces.  I think traditionally
anything in the UNIX man pages section 2 was referred
to as a system call. 

I pulled out my printed copy of 1003.1b-1996 and found
the words function, interface, and service in a quick scan.

If someone has a clue what the preferred POSIX term is,
I would be happy to see the manual use it.
> Anyone can explain me what is the difference between this three types of
> API functions?
>   
Nothing really that technically matters.
>
> Thanks,
>
> Ricardo
>
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>   


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Joel Sherrill, Ph.D.             Director of Research & Development
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