4-UNIX-Overview

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

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