questions

how do the following standards relate: ISO-C, POSIX,XSI,SUS.
can you give an example of a specific POSIX requirement
crazy4sAsked:
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phoffricConnect With a Mentor Commented:
ISO "International Organization for Standardization) is an international-standard-setting body composed of representatives from various national standards organizations." Once an ISO document with a name has been written, then a product may claim to conform to this document (with exceptions noted). Then all users of the product have confidence that the product will serve in a specified way. Often there is some verification process to assure conformance.

Then a compiler that says it is ISO-C compliant assures the reader that a program written for this compiler will, in fact, compile on another platform whose compiler also claims to be ISO-C compliant. But, as you may know, the program may not work on another platform due to other issues (e.g., endianness, size of an int). However, this compliance improves the probability that the program will work as desired and reduces the amount of code changes necessary when porting to another platform.


XSI

According to the above link, XSI is "X/Open System Interfaces Extension, a supplementary specification to the Single UNIX Specification" (i.e., SUS).

SUS

"The SUS emerged from a mid-1980s project to standardize operating system interfaces for software designed for variants of the Unix operating system."

It wasn't enough to just standardize the C language. OS interfaces also needed to be standardized to promote ease of portability.


POSIX is one of these standards to improve portability. For example, it provides a uniform approach in handling multi-threading by providing additional POSIX libraries with a uniform API to the C (and C++) language. So, a multi-threaded program on one POSIX compliant OS should port fairly well to another similar OS.
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crazy4sAuthor Commented:
but how these four are related to each other?
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Dave BaldwinFixer of ProblemsCommented:
That would be a long essay in itself.  You need to read the articles and maybe more to understand the ways they are related.
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crazy4sAuthor Commented:
thanks:)
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