Monday

UNIX and Linux

The development of UNIX began in 1969 by the MULTICS developer Ken Thompson. He tried to create an easy-to-use operating system for mainframe computers without the typical batch operation. In the times before UNIX, most of the operating systems were batch operating systems. This means that you had to “write” the application that you want to run on a computer onto a punched card or onto a batch of punched cards. The result was usually printed out. If there was an error, you had to replace or change one or more of the punched cards and start over again. This system was lengthy and expensive so people wanted a system were more people can work in dialogue with the computer. The first step in this direction was the operating system called “MULTICS”. However, MULTICS was hard to handle and still batch operated.
The first version of UNIX was written in the programming language Assembler. Assembler is a programming language that is close to the computer platform on which it is installed. To provide 
independence of the computer platform, the UNIX was re-written in “C”. “C” is a programming language that was developed in 1971 by
Dennis Ritchie. 
In 1974, UNIX was described for the first time. At this time, it had multi-user and multi-tasking capabilities. Every user had his own “home directory” with his files; no user could access files of other users. That was elementary for a multi-user operating system. Multi- user operating systems were needed urgently because many people had to share one mainframe computer. Ken Thompson developed the UNIX system for his employer, the Bell Laboratories. Bell Laboratories is a 100% subsidiary company of AT&T. The Bell Laboratories gave the documentation for UNIX and the source code for nearly the cost price to universities. Besides,
AT&T was doomed in an Antitrust-procedure in 1956 to give away licenses on all his patents. Therefore, many different UNIX systems came into being. These systems are all UNIX-systems but differ in details.
Historically, Linux distributions have mainly been used as server operating systems, and have risen to prominence in that area; Netcraft reported in September 2006 that eight of the ten most reliable internet hosting companies ran Linux distributions on their web servers. (As of June 2008, Linux distributions represented five of ten, FreeBSD three of ten, and Microsoft two of ten. This is due to its relative stability and long uptime, and the fact that desktop software with a graphical user interface for servers is often unneeded. Enterprise and non-enterprise Linux distributions may be found running on servers. Linux distributions are the cornerstone of the LAMP server-software combination (Linux, Apache, MySQL, Perl/PHP/Python) which has achieved popularity among developers, and which is one of the more common platforms for website hosting. Linux distributions are commonly used as operating systems for supercomputers. As of August 2008, out of the top 500 systems, 423 (84.6%) run a Linux distribution. Nevertheless, the use of the different UNIX-systems was restricted by licenses and rules, made by the manufacturers. Besides, UNIX programs were given away only in binary code that is (nearly) unreadable for humans.


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