What are UNIX® and Unix?

"You need Unix-level performance and reliability. You don't have a Unix-level budget."
— Microsoft advertisement (2003)

By Unknown author —
      http://catb.org/~esr/jargon/html/U/Unix.html, Public Domain,
      https://commons.wikimedia.org/w/index.php?curid=31308 Unix is one of the oldest operating systems, originally coded in assembler in 1969 by Dennis Ritchie (right) and Ken Thompson (left) at Bell Labs.

In 1972, Unix was coded again in C (its native language) for portability. Unix is the most portable and reliable OS.

By the way, UNIX® is not the same as Unix. UNIX® (in upper case letters and often presented with the copyright symbol) is a trademark while Unix (in proper case, proper name) is a philosophy and an IEEE standard — Portable Operating System Interface (POSIX).

Several vendors have registered versions of UNIX®. They are Tru64 Unix, IBM AIX, UnixWare, IRIX and Sun Solaris.

There are also several clones such Linux. This means that these are not UNIX®. They UNIX® clones, but nonetheless they are considered Unix. If you are confused, you are not alone.

About 90% of the internet relies on a variation of Unix (normally either Linux or BSD), with Apache Software Foundation (ASF) or related technology.

Support the open source community. One way you can do this is by supporting organizations like the Open Source Education Foundation.

If you are interested in learning Unix as well as its clones or other derivatives, you should learn how to use, at least, one shell.

Installing Unix (or Unix Clones):

Unfortunately I have no experience installing or using Tru64 Unix, IBM AIX, UnixWare, IRIX or Sun Solaris. I have experience BSD and Linux though.

Some of the information mentioned in this page was partially taken from IBM DeveloperWorks.

Unix Emulators:

Cygwin

Cygwin is an open source "Linux-like environment for Windows [4.x and up]" (emulator) originally developed by Cygnus Solutions and then acquired by Red Hat.

GitHub for Windows

GitHub offers a limited open source emulator for Windows in order to access the Git version control system. This emulator is often the choice of open source developers using Windows. As of 2018, GitHub became part of Microsoft.

Termux (Android)

Termux is an open source emulator and Linux environment for Android with its own package manager (pkg) in a sandbox — little to no chance to destroy or corrupt data.

          
          pkg install [package_name]