Unix and Linux Introduction

UNIX Introduction:

1. UNIX was developed in 1969 at AT&T Bell Labs by Ken Thompson and Dennis Ritchie and first time UNIX was developed using BCPL (Basic Combined Programming Language) and it’s also known as B Language.
2. In between 1972-1973 the system was rewritten in the programming language C to give the system more portability options. They wrote and debugged almost 100,000 code lines that year.
3. C programming language was developed in 1972 by Dennis Ritchie.
4. Based on core Unix then different types of variants were developed like BSD, Solaris, Mac OS X, Linux
5.  Some of the Commercial Unix variants are
   –> Apple            –     Mac OS X, (Mac OS is a certified Unix OS)
   –> HP                 –     HP-UX,
   –> IBM               –     IBM-AIX,
   –> SUN              –     SUN OS (SunOS was originally based on the BSD (Berkeley Software Distribution) flavour of UNIX.
   –> Santa Cruz   –    SCO- UNIX
   –> Sun microsystems (oracle) –   Solaris (Solaris, was the suc­cessor of SunOS)
   –> Microsoft   –   Xenix MS Dos
6. Linux is nothing but a UNIX clone which is written by Linus Torvalds.
   

LINUX Introduction:

1. Linux and UNIX are different but they do have a relationship with each other as Linux is derived from UNIX.
2. The Linux Kernel was first developed in 1991 By a Finnish college student Linus Torvalds 
3. By 1991 there were growing requirements for a free commercial alternative. UNIX was growing, but at that time in its history the source code was observed very carefully because it do not want anyone else to have it and expensive to use.
4. Therefore, Linus Torvalds set out to create new free operating system kernel that eventually became Linux. It belongs to nobody, and is free to download and use. Any changes to it are open for all to adopt, and as a result it has developed into a very powerful OS that is rapidly gaining in popularity worldwide, particularly among those seeking an alternative to Windows.
5. The Linux kernel code was completely written from scratch. It is designed in such a way so that it acts like UNIX but it does not have the original UNIX code in it.
6. Linux is just the kernel and not the complete OS. This Linux kernel is generally packaged in Linux distributions which thereby makes it a complete OS.
7. Different organizations have combined the available components (additional features) differently. Each combination is called a “distribution”, and the organizations that develop distributions are called “distributors”.
8. Thus, Linux distributions actually make the Linux kernel completely usable as an operating system by adding different applications to it. There are various flavours of Linux distributions that serve a wide range of user needs.Red hat, Centos, Ubuntu, Fedora, SUSE, Slackware, Mandrake 
9. A standard Linux distribution consists of a Linux kernel, GNU system, GNU utilities, libraries, compiler, additional software, documentation, a window system, window manager and a desktop environment.
10. Most of the software included in Linux distribution is free and open source. 
11. Linux was given to GPL (General public License) organized by GNU. 
12. Linux was widely adopted for servers and embedded systems.
13. Linux is now one of the most used systems for the PC, and is particularly suitable for businesses with small IT budgets. Linux is free to use and install, and is more reliable than almost all other systems, running for many months and even years without a reboot being necessary.