UNIX OS
The UNIX operating system was developed in the late 1960’s at AT&T Bell labs by Ken Thompson and Dennis Ritchie. UNIX is a command-line based operating system originally designed for use by computer programmers. The UNIX operating system consists of three parts: the kernel, the shell, and programs. The kernel is the center of the operating system and manages time and resources allocated to programs, as well as communications and storage. The shell is the command line interface between the kernel and the user. When the user types commands into the shell, the shell searches the filesystem for the program being requested by the user and then requests the kernel execute the program. In this fashion the kernel and shell work together to execute commands requested by the user. The programs are the tools and applications that are used to perform the tasks being requested by the user.
The first version of UNIX was not designed for multi-tasking and was written in assembly language which prevented it from being ported to other platforms. However, in 1973 UNIX version 4 was rewritten in C which eventually led to the operating system becoming suitable for porting to other platforms in 1978. Due to the growing popularity of UNIX, AT&T went from using the operating system exclusively, and began to license different versions of UNIX for academic and commercial use. However, this resulted in AT&T implementing stricter licensing terms which increased the cost of using UNIX and made it less attractive to companies. This eventually led to the development of UNIX-like operating systems that did not have AT&T’s proprietary code but the similar design where the operating system consisted of the three main parts that UNIX is known for, the kernel, the shell, and the programs.
The two most popular versions of UNIX-like operating systems that were developed at the time were BSD (Berkeley Software Distribution) and GNU (GNU’s Not Unix). Both versions were created for use in academics and were open source. This removed the licensing restrictions implemented by AT&T and allowed access to the source code of the operating system so that programmers could modify the software. This allowed programmers to fix bugs, create enhancements, and even create specialized versions of the UNIX operating system. This resulted in decreasing the cost of software, improving the stability and security of the operating system. Some current examples of UNIX-like operating systems that are in use today are MAC OS X, Linux, and Android.
Resources:
https://en.wikipedia.org/wiki/Unix
