POSIX was only concerned with how an application interfaces with the operating system. It’s important to note that POSIX wasn’t formed to control how the operating systems were built – any company was free to design their UNIX variant any way they pleased. The standard was defined based on AT&T’s System V UNIX and BSD UNIX, the two biggest variants at the time. To solve this portability issue POSIX was formed in the 1980s. The promise of UNIX portability was losing ground. However, when UNIX started to fork into different flavors, porting code across these UNIX variants became difficult. When UNIX came about, around the same time, it also showed promise in that it could operate on machines from different manufacturers. It’s all common today – networks and systems, but back then, this was a huge deal!
Not only did this keep costs low, but it created computer systems – systems across a product line that could work together. Not only could the operating system run on different models, applications could run on them as well. Different models had their unique specializations, but the hardware was such that they could use the same operating system: OS/360. IBM introduced the System/360 family of mainframe computers. This didn’t happen all that often due to the expense involved, but portability became a feature in the mid-1960s – not through POSIX – but in the mainframe arena. Over 60 years ago, programmers had to rewrite code completely if they wanted their software to run on more than one system. POSIX covers such things as: System Interfaces, and Commands and Utilities, Network File Access, just to name a few – there is much more to POSIX than this. POSIX’s focus is primarily on features from AT&T’s System V UNIX and BSD UNIX.Ī standard must be spelled out and followed by rules on how to achieve the goal of interoperability between operating systems.
It is an IEEE 1003.1 standard that defines the language interface between application programs (along with command line shells and utility interfaces) and the UNIX operating system.Ĭompliance to the standard ensures compatibility when UNIX programs are moved from one UNIX platform to another. POSIX is shorthand for Portable Operating System Interface.
A standard consists of sets of rules and instructions that POSIX is concerned with. Imagine a box labeled: POSIX, and inside the box is a standard. It describes a thing – much like a label.
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