It would be awkward and hard to believe that OS in the 21st century had their roots back from the 1969 when Dennis Ritchie and Ken Thompson came up with a whole new programming language (at that time) known as C Programming Language and the first Unix at the AT&T Bell Labs.
The source code was shared with everybody around the globe, including hippies from California.
By 1975, Unix gained a commercial value. Since half of the code was written by the hippies, they were unhappy with the fact that the software they had written was being sold. They dragged the matter to court and the result gave birth to 2 versions of Unix namely: AT&T Unix and BSD.
Furthermore, in the 80s, many companies started to develop their own Unix; for example, IBM created AIX. This is the first real start of Linux. As there were many different ways of doing the same thing and to end the era of Unix separation, Richard Stallman, encouraged everybody to start afresh with the GNU project. His sole aim was to make an OS that would be freely available and encourage everybody to work together like the 70s.
Then, in the 90s, Linus Torvalds, a student bought 386 computers and wrote a new POSIX compliant kernel. Thinking that it would only support 386 hardware, the code was put online. Many people embraced the combination of the kernel and GNU and it can be said that the rest is history.
Coming back to the 21st century, Linux powers more than 90% of the world’s most powerful supercomputers, more than 60% web servers and millions of appliances.
The kernel’s source code grew by several thousands lines with a huge number of contributors such as Google, Intel, AMD, ORACLE, Samsung, and many more….
It is easily deduced that Linux is by far the most used OS in the world!