Agenda Attention
$ Overview of UNIX These PowerPoint notes are based on $ Purpose of an Operating System (OS) Chapter 1 of textbook A Practical $ History of Unix OS Guide to Linux $ Characteristics of Unix OS $ History of Linux OS $ Read pages 3 to 17 $ The Drive for compatibility (POSIX standards)
Definition of an Operating System (OS) History of Unix OS
An operating system is a control $ Prior to Unix, many operating systems ran program for a computer that performs collections or batches of operations one at a the following operations: time. $ This single−user batch−processing approach $ allocates computer resources did not take advantage of the potential $ schedules routine tasks processing power and speed of computers $ provides a platform to run application software for users to accomplish tasks Enter data in Process Receive files to be later Collection or information of $ provides an interface between the user & processed Batch of files processed data the computer Note: batch processing lacks the advantage of immediate feedback as opposed to online processing History of Unix OS History of Unix OS
$ The Unix OS was developed (based on $ The first versions of UNIX were written Multics & CTSS operating systems) by Ken in machine−dependent programs Thompson at the AT&T Bell Laboratories in (such as PDP−7). 1969. He wanted to create a multi−user operating system to run space travel game. $ Ken Thompson approach Dennis $ Kens philosophy was to create an operating Ritchie (developer of C language), and system with commands or utilities that in 1973 they compiled UNIX in C would do one thing well (i.e. UNIX). Pipes programming language to make could be used combine commands... operating system portable to other computer systems.
History of Unix UNIX Features
$ The Unix OS is a multi−user OS allowing $ Ken Thompson (recently retired more than one person to directly from Bell Labs) communicate with the computer. is on left, and $ Although the OS can only work on one task Dennis Ritchie is at a time, a small piece of time (time slice) is in the middle. dedicated to each task or user − this is Whats his name referred to as time−sharing. is on the right $ Time sharing gives the illusion that the CPU is giving all the users its full attention Illustration of Time−Sharing Development of Unix OS
Unix became a popular OS among institutions such as colleges & universities User 8 User 1 through a 4−year try before you buy deal.
User 2 User 7 $ Efficient and inexpensive way of networking $ Promotes Internet use and file−sharing User 6 User 3 $ Open system allows for source code to be shared among many programmers − allows for better User 4 TIME User 5 coordination among programmers
Development of Unix OS Development of Unix OS
Students at University of California (in There were versions of UNIX for the Berkley) further developed the UNIX Personal Computer (PC), such as operating system and introduced the XENIX, etc., but they didnt catch on in BSD version of Unix popularity until Linux was developed in the early 90s. Unix
Bell Labs Berkley Software Distribution UNIX System V (5) (BSD) Proprietary Free Why Has Linux Become so History of Linux Popular?
$ Linux operating system Linus decided to make Linux OS developed by source−code for Linux Kernel open to all: programming student Linus Torvalds $ Unlike traditional Operating Systems, anyone can modify and distribute Linux OS (as long as they $ Linus wanted to distribute source code of Linux Kernel) develop Unix−like OS $ Competition among Hackers allows code to be just to experiment with improved and distributed often new 386 computer at $ Many users can spot bugs in the operating system the time... or application if source code is open
Why Has Linux Become so Popular? Concerns
Other Factors: $ Some people claim that there are as many $ PCs have increased processing power and there version of Linux as there are users has been a shift from mainframes and $ POSIX (Portable Operating System Interface minicomputers to PCs. for Computer Environments) is a government $ Since Linux is a Unix Work−alike, this OS has a standard to ensure consistency among reputation of being a very stable platform for different UNIX and Linux versions. networking (creating at−home servers) and $ running / maintaining applications. Many versions of Linux are approaching POSIX standard. $ Agencies such as Free Software Foundation created the GNU project to provide free software. Concerns
$ Freedom of allowing Linux users to create servers connected up to Internet can lead to attacks from experienced hackers. $ Linux commands may be considered user− unfriendly although GUIs are now used. $ Prior reputation for difficult install process including the loss of data on other hard disk partitions.