History of UNIX a short version CSCI 333 August 31, 2011

Before UNIX  In the 40’s and 50’s, all computers were “personal computers”  That is, one person signed up for an hour of computing time  In the 60’s, batch systems with punched cards were the way of life

Multics  In 1965, a collaborative project by GE, MIT and AT&T  Goal: Create an operating system to “show that general-purpose, multi- user, timesharing systems were viable.”  Name: Multics (Multiplexed Information and Computing Services)

Multics  In 1969, frustrated by slow progress, AT&T pulled out of the project  Ken Thompson, of AT&T, needed something interesting to do  He took over an unused DEC PDP-7 (minicomputer) and pursued some of the Multics ideas on his own (most of which were shot down by AT&T)PDP-7

Ken Thompson  The code was written using assembly language  It was much simpler than Multics  It was good at running programs  Another researcher at Bell Labs jokingly referred to it as UNICS (Uniplexed Information and Computing Services)

Dennis Ritchie  In 1970, Thompson along with Dennis Ritchie and others, rewrote UNIX for a new PDP-11 (this was the dominant minicomputer in the 70’s...it had 24K RAM, 12K of which for UNIX…it only cost a mere $65,000)Thompson along with Dennis Ritchie  More tools were added, such as a shell, editor, assembler, utilities like rm, cat, and cp

B  In 1972, Thompson wrote B, a very simple programming language  He got it going on the PDP-7 because Fortran wouldn’t work for him  He wanted to re-write UNIX in a high- level language

C  In 1972, Ritchie used the PDP-11 to add types to B  Initially, it was called NB, “New B”  Then, he wrote the compiler  The C programming language was born  C was designed to be simple and portable

Re-writing UNIX  In 1973, Thompson re-wrote UNIX using C  Operating systems written in assembly language consisted of hardware-dependent code  An operating system written in a high-level language, such as C, allowed it to be portable  The kernel consisted of 10,000 lines of code  Many features of other O.S. kernels were left out of the UNIX kernel (e.g., the command language ran as a user process)

The spread of UNIX  In 1974, Ritchie and Thompson published a paper about UNIX  Many universities were interested  AT&T licensed UNIX for a modest fee  Releases were distributed as C source code  By 1977, more than 500 sites (125 universities) were running UNIX

BSD  Graduate students at the University of California Berkeley began making significant enhancements to the source code  In 1978, they released 30 copies of their Berkeley Software Distribution (BSD): Easy to switch between programs Longer filenames (255 vs. 14) Easy to connect UNIX machines to LANs

Versions / Flavors of UNIX  Under agreement with AT&T, organizations could release minor updates without renegotiating contract  DEC and Sun adopted the Berkeley UNIX  Data General, IBM, HP, and Silicon Graphics were among those that adopted the AT&T (“standard”) System V  In 1980, Microsoft developed XENIX  In the early 90s, Linux and Solaris were created

Different versions of UNIX  To find out what you are responsible for knowing about UNIX versions on Exam #1, click on the link below:  Exam #1 Outline Exam #1 Outline  IEEE Portable Operating System Interface (POSIX) is an attempt to standardize UNIX (among other things)

Pioneers of computing…today