4-UNIX-Overview - THE UNIX OPERATING SYSTEM CS252: SYSTEMS...

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Unformatted text preview: THE UNIX OPERATING SYSTEM CS252: SYSTEMS PROGRAMMING Charles Killian Computer Science Department Purdue University With slide credits to Gustavo Rodriguez-Rivera and others. What is an Operating System An Operating System (OS) is a program that sits in between the hardware and the user programs. It provides: Multitasking - Multiple processes running in the same computer Multiuser - Multiple users using the same computer File system Storage What is an Operating System An Operating System (OS) is a program that sits in between the hardware and the user programs. It provides: Multitasking - Multiple processes running in the same computer Multiuser - Multiple users using the same computer File system Storage Networking Access to the network and internet What is an Operating System Window System Graphical use interface Standard Programs Programs such as a web browser, task manager, editors, compilers etc. Common Libraries Libraries common to all programs running in the computer such as math library, string library, window library, c library etc. It has to do all of the above in a secure and reliable manner. A Tour of UNIX We will start by describing the UNIX operating system (OS). Understanding one instance of an Operating System will help us understand other OSs such as Windows, Mac OS, Linux etc. UNIX is an operating system created in 1969 by Ken Thompson, Dennis Ritchie, Brian Kernighan, and others at AT&T Bell Labs. UNIX was a successor of another OS called MULTICS that was more innovative but it had many problems. UNIX was smaller, faster, and more reliable than MULTICS. A Tour of UNIX UNIX was initially created to support typesetting (edition of documents). By having the programmers being the users themselves of the OS (it your own food), UNIX became the robust, practical system that we know today. UNIX was written in C (95%) and assembly language (5%). This allowed UNIX to be ported to other machines besides Digital Equipment (DEC) s PDP11. BSD UNIX UNIX was a success in the universities. Universities wanted to modify the UNIX sources for experimentation do Berkeley created its own version of UNIX called BSD-UNIX. POSIX is an organization that created the POSIX UNIX standard to unify the different flavors of UNIX. Sockets, FTP, Mail etc came from BSD UNIX. THE UNIX FILE SYSTEM UNIX File System UNIX has a hierarchical File System Important directories / - Root Directory /etc OS Configuration files /etc/passwd User information /etc/groups Group information /etc/inetd.conf Configuration of Internet Services (deamons) /etc/rc.*/ - OS initialization scripts for diffeerent services....
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This note was uploaded on 02/21/2012 for the course CS 252 taught by Professor Gustavorodriguez during the Spring '11 term at Purdue University-West Lafayette.

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4-UNIX-Overview - THE UNIX OPERATING SYSTEM CS252: SYSTEMS...

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