Operating System•Different concepts-single user-multiprogramming-multi-user1234567Linux-a free Unix-type OS-adheres to the POSIX standard: Portable Operating System Interface [for Unix]-what came before?8MULTICS•Multics (Multiplexed Information and Computing Service)•mainframe area•early OS (late 60s)•last Multics system shut down in 2000, Canadian Dept. National Defense9UNICS•Ken Thompson wanted “fast” response OS for “Space Wars” game-implemented UNICS (“UNI” versus “MULTI” from Multics)-implemented in assembly language for PDP-710UNIX•Dennis Ritchie suggested to rewrite the OS using C -which he had developed from B-initial concern that C would not be fast enough-still some assembly code-Bell Labs started using this UNIX and utilities like nroff and troff were developed11BSD UNIX•Improvements made to Unix by UC Berkeley grad students•first good memory management system•first real networking capability•1970 BSD UNIX was distributed to general public12System III and V•Breakup of Bell Systems allowed AT&T to start selling UNIX licenses•System III and System V (mid 80s)•later System V Release 413Evolution•No clear winner between System V and BSD Unix. Following are System V based, but incorporate BSD features:•Solaris (Sun Microsystems)•HP-UX (HP)•AIX (IBM)•IRIS (Silicon Graphics)14Open Source Software•Free software? -freedom to use, view, and modify•Early days: Richard Stallman wrote version of Emacs and made available to public-he started GNU Project “GNU’s not Unix”-GNU C Compiler•Free Software Foundation http://www.fsf.org15Linux•Linus Torvalds posts message in newsgroup-who wants to participate? 1991-playing with MINIX he wanted to write “performance code”-release of Linux 1.0 (Linux = Linus’ Minix) under GNU GPL (General Public License) in 1994-first a few friends - now thousands of volunteer developers-1996 Linux 2.0 became major competitor to other OSs, including commercial Unix16Linux vs Unix•They are not the same! •no shared code•but: same POSIX standard•look and feel almost the same•BUT under the hood they are
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