The history of UNIX starts back in 1969, when Ken Thompson, Dennis Ritchie and others started working at Bell Labs what was to become UNIX .Originally written in assembler, UNIX was re-written in C in 1973. Here are some features of UNIX:

  • Unix is divided into two constituents:
    • Kernel: Communicates with the hardware of a machine directly.
    • Shell: Interprets the commands given by the user so that the kernel can read, understand and execute the command.
  • Unix is comprised of number of small commands, which performs one simple job only. These commands can be grouped together to achieve a complex task.
  • Unix provides a very strong pattern matching capability with the use of metacharacters.
  • Unix is highly programmable since it was designed keeping a programmer in mind. Shell programming can achieve what many development languages like C++ are capable of doing.
  • Unix is a Multi-Tasking, Multi-User Operating System.
  • Unix provides vary high level of Security and Networking support.
  • And most importantly, UNIX is an Open System means you can get the source code freely and encorporate new custom made changes.

All these features make UNIX a very powerful Operating System.

One more advantage in UNIX is that a job can be run in the background in the same shell whereas in windows this is not possible. So one can write a piece of shell-script and keep running the same in the background that would work just like a service on windows.

UNIX Flavors and Versions

UNIX has changed a lot since it was first developed in 1969. Many new features have been added to make it more efficient and robust. Many vendors and many flavors of Unix are available today. Linux, Solaris, AIX, HP-UX and Tru64 are some of the popular ones.

The major difference between these flavors is their vendor. IBM has its own hardware and they created AIX that would work well on their hardware. Similarly, HP invented HP-UX. Solaris works on SPARC based architecture. In all these flavors, the kernel is the same although the file system may vary. Above all, Linux itself comes from different vendors like RedHat, Mandrake, Novell (Suse) etc.

There are few basic differences between these flavors like the default shell on Red Hat Linux is Bash whereas on Solaris it is Csh. They handle metachars differently.

The file format on Linux is ELF (Executable & Linking Format) while on AIX and Solaris it is COFF (Common Object File Format).

When we say UNIX Flavors, it means that these OS follow some rules in order to qualify as a UNIX OS. All that an OS needs to qualify, as a UNIX OS is that it should be a POSIX (Portable Operating System Interface) compliant. POSIX is a set of rules or policies defined just like ISO (International Organization of Standards) or CMM (Capability Maturity Model), so that these flavors have the basic, important and frequently required features available all the time.

Soon I’ll be covering some more details about this topic..

~Himanshu

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