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POSIX compliance for portability

What Linus was trying to do was make a system that essentially was close enough to POSIX compliant to let him compile and run his programs.
He was 1 year into C programming so no "Unix" genius was he. Just a hobiest trying to make it work. Tanembaums Minix book is great because it has complete source and a discussion of the system. Minix was POSIX like but definitly not a BSD or AT&T Unix like system under the hood.
The POSIX compliance makes stuff user like at the application program level. Below the POSIX level it can be anything including Windows.

http://www.ee.ic.ac.uk/docs/software/unix/begin/appendix/history.html
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The IEEE/ISO (i.e. neutral) POSIX (Portable Operating System) standard is the intersection of the kernel services (not the union) provided by both the BSD and SVR4 which in effect corresponds to version 7. It has added BSD signals and terminal handling which is new. In fact since POSIX translates POSIX compliant calls to the calls of the target operating system, it can appear on any platform, and hence appears on non-UNIX systems like DEC-OpenVMS and Microsoft Windows NT. Ironically, any Operating System can be rewritten using POSIX calls at the source code level, thus a user can continue to use their favourite Operating System (which does not have to be UNIX) whilst the programmer has an easier task of achieving portability. All the major workstation vendors have accepted POSIX 1003.1 for their UNIX implementations thus providing source code portability. Hence, if UNIX is not the operating system of the future, then the operating system that is, will have been inspired by UNIX and will probably look a lot like UNIX.
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Again I say you are calling stuff Unix if it is based on POSIX compliance. That definies Unix compatibility. There are many ways to write an OS underneath the POSIX compliance.

Linus programed towards a POSIX like compliance which is why the system is Unix like and why it can use a lot of Unix code directly.

There is a big difference between what the car looks like and how it drives. POSIX and "Unix like" specify what the car looks like. They do not describe what is under the hood.

Posted by: rgriffith64@...   Posted on: 12/18/03 You are currently: a Guest | Members login | Terms of Use

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