Life and Work of Ken Thompson and Dennis Ritchie | Turing Techtalk

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Life and Work of
Ritchie & Thompson
July 27, 2013

2
ACM A. M. Turing Award
Dennis MacAlistair Ritchie and
Kenneth Lane Thompson
United States – 1983
Citation:
For their development of generic
operating systems theory and
specifically for the implementation of
the UNIX

3
Denis Ritchie (Sept 9, 1941 – Oct 12, 2011)
 Born: 9 Sep1941, New York, USA
 Education:
 Ph. D. in Physics and Applied Mathematics, Harvard,
1967
 Professional Career:
 Joined Bell Laboratories as Member Technical Staff after
graduation
 Became head of the Bell Laboratories Computing
Techniques Research Department in 1990
 Retired as head of Lucent Technologies' System
Software Research Department in 2007
 Died on 12 October, 2011
Home Page: http://cm.bell-labs.com/who/dmr/

4
Ken Thompson
 Born: 4 Feb1943, New Orleans, USA
 Education:
 EECS Bachelor of Science (1965) and master's degree
(1966), Electrical Engineering and Computer Science,
University of California, Berkeley
 Professional Career:
 Joined Bell Laboratories as Member Technical Staff after
graduation
 Retired from Bell Labs in 2000 and became a Fellow at
Entrisphere Inc. until 2006
 Currently at Google Inc. as a Distinguished Engineer
since 2006
Home Page: http://www.cs.bell-labs.com/who/ken/

5
Ritchie and Thompson – Joint Awards/Honors
 ACM Programming Systems and Languages Paper
Award (1975)
 ACM A. M. Turing Award (1983)
 ACM Software System Award (1983);
 IEEE Emmanuel R. Piore Award (1983)
 IEEE Richard W. Hamming Medal (1990);
 IEEE Computer Pioneer Award (1994);
 Computer History Museum Fellow Award (1997);
 1998 National Medal of Technology from President Bill
Clinton; ACM SIGOPS Hall of Fame Award (2005).
 Japan Prize for Information and Communications (2011).

6
Video Introduction of Dennis Ritchie and Ken Thompson at the 27th
Japan Prize for Information and Communications
http://www.youtube.com/watch?v=IjvjqAVkvYo
Duration: 8 mins

7
Early Unix History – A Chronology
1940 - 1968
1941 Dennis Ritchie born
1943 Ken Thompson is born.
1963 Project MAC (Multiple Access Computers) is organized at MIT to do
research on interactive computing and time-sharing systems.
1965 AT&T, GE, and Project MAC at IBM join together to develop the
time-sharing system MULTICS (Multiplexed Information and Computing
Service).
1966 Ken Thompson finishes studies at UCB and joins technical staff at
AT&T Bell Labs to work on MULTICS.
1968 Dennis Ritchie completes work on his doctorate at Harvard and
joins Bell Labs to work on MULTICS project.
Adapted from http://snap.nlc.dcccd.edu/learn/drkelly/hst-hand.htm

8
Early Unix History– A Chronology
1969
1969
AT&T Bell Labs drops out of MULTICS project. A system which was supposed to support
1000 on line users can barely handle three. Out of the ashes grows the most influential
operating system in history.
Thompson gets an idea for a new type of file system and hashes out his ideas with Ritchie
and Rudd Canaday.
Thompson writes first version of UNICS for PDP-7 in one month while wife is on vacation.
He allocates one week each to the operating system functions: the kernel, the shell, the
editor, and the assembler. He does this on a machine with 4K of 18 bit words. UNICS is pun
on MULTICS and stands for Uniplexed Information and Computing Services. Name is
changed to UNIX which is not an acronym. This version is in assembly language.
Thompson develops the interpretive language B based upon BCPL. Ritchie improved on "B"
and called it "C"

9
1970-1973
1970
DEC begins shipping PDP-11 and revolutionizes the computer industry by selling 250,000
systems.
Bell Labs gets a PDP-11 to do text processing for the legal department. System is
developed and implemented in UNIX. The standard DEC OS is never installed.
1971 The First Edition of UNIX manual is written.
1972 UNIX OS is rewritten in C which opened the door for porting.
1973
First UNIX development support group is formed in Bell Labs.
Thompson delivers first UNIX paper at the ACM Symposium on Operating Systems at the
Thomas J. Watson Research Center in Yorktown Heights, NY.
Within six months, the number of UNIX sites triples from 16 to 48.

10
1974-75
1974
"The UNIX Time-Sharing System" is published in CACM by Ken Thompson and Dennis
Ritchie. It is a revision of the 1973 paper.
University of California at Berkeley (UCB) gets Version 4 of UNIX.
Keith Standiford converts UNIX to PDP 11/45.
Berkeley begins making major enhancements to UNIX and sets the stage for becoming a
major distribution center for their version of UNIX.
The Elements of Programming Style by Kernighan and Plauger is published.
1975
Thompson begins one year sabbatical at Berkeley.
AT&T officially begins licensing UNIX to universities.

11
1976-77
1976
Software Tools by Kernighan and Plauger is published.
Boggs and Metcalfe invent Ethernet at Xerox in Palo Alto.
1977
UK UNIX Users Group is formed as Special Interest Group (SIG) in DECUS UK.
INTERACTIVE Systems develops the first commercial version of UNIX (IS/1) on a
PDP-11.

12
1978
Bill Joy produces first Berkeley Software Distribution (BSD) of UNIX.
UNIX ported to an Interdata 8/32, the first non-DEC computer to run UNIX after
nearly ten years of running only on DEC equipment.
UNIX is ported to a DEC VAX, but not by Thompson and Ritchie, since they had
become disenchanted by DEC and its unwillingness to support UNIX. DEC's
refusal to support UNIX must be one of the all time great blunders of the
computer industry.
The C Programming Language by Kernighan and Ritchie is published.
P.J. Plauger forms Whitesmiths Ltd and writes the first commercial C compiler.
The USENIX UNIX users group is formed.
Doug and Larry Michels start Santa Cruz Operations, Inc. (SCO) to sell UNIX on
a PC. By 1992, they grow to $175 million in revenues.

13
1979-80
1979
Seventh Edition UNIX PROGRAMMERS MANUAL (UNIX Version 7) is published. It is the
first edition without Thompson's or Ritchie's names. It is titled "UNIX (with a TM sign) Time-
Sharing System." Bell Labs starts to protect its assets.
Microsoft licenses UNIX from AT&T and announces XENIX, which is soon overshadowed by
MS-DOS.
1980
BSD UNIX finds its way back into Bell Labs as a new improved version.
Berkeley lands large DARPA contract and forms Computer Systems Research Group
(CSRG).
SCO becomes a distributor for Microsoft XENIX and licenses the name XENIX because
they sold their trade name DYNIX to Sequent.

14
1981-83
1981
The IBM PC is released running Microsoft DOS; XENIX is pushed into the background.
Amdahl develops the first mainframe version of UNIX (UTS).
1982
AT&T announces official support for UNIX and its first commercial release: UNIX System III.
Bill Joy, the inspiration behind BSD, leaves Berkeley to co-found Sun Microsystems. SUN
gets its name from the Stanford University Network (SUN) board. Sun workstation is based
on the Motorola 68000 chip running SunOS based on 4.2BSD. It includes an optional local
area network based on Ethernet.
HP announces support for UNIX (HP/UX) on its 9000 workstations.
DEC releases ULTRIX.
IBM releases CPIX.
1983 Thompson and Ritchie receive ACM Turing award for their work on UNIX.

15
1981-83
1981
The IBM PC is released running Microsoft DOS; XENIX is pushed into the background.
Amdahl develops the first mainframe version of UNIX (UTS).
1982
AT&T announces official support for UNIX and its first commercial release: UNIX System III.
Bill Joy, the inspiration behind BSD, leaves Berkeley to co-found Sun Microsystems. SUN
gets its name from the Stanford University Network (SUN) board. Sun workstation is based
on the Motorola 68000 chip running SunOS based on 4.2BSD. It includes an optional local
area network based on Ethernet.
HP announces support for UNIX (HP/UX) on its 9000 workstations.
DEC releases ULTRIX.
IBM releases CPIX.
1983 Thompson and Ritchie receive ACM Turing award for their work on UNIX.

16
Video: Ken Thompson and Dennis Ritchie Explain UNIX (Bell Labs)
http://www.youtube.com/watch?v=JoVQTPbD6UY
Duration: 3 mins

17
The UNIX-11 Time-Sharing System
(CACM Paper, July 1974)
http://pdos.csail.mit.edu/6.828/2004/readings/ritchie74unix.pdf
 General-purpose timesharing operating system DEC PDP-11 machines
 Operational from Feb 1971, the System used by the Patent Division at
Murray Hill to prepare Patent Applications
 Hardware (PDP 11/45)
 16-bit word (8-bit byte)
 144Kb of core memory – Unix occupies 42Kb
 1 Mb fixed-head disk used for file system storage and swapping
 4 Moving-head disks – removable 40Mb disk packs
 Paper tape reader-punch, Lineprinter
 Console teletype and communication interfaces for character terminals

18
The UNIX-11 Time-Sharing System (CACM Paper)
 In addition to the system proper
 C Compiler
 Text Editor
 Linkloader
 Symbolic Debugger
 BASIC Interpreter
 Fortran Compiler
 SNOBOL Interpreter
 Top-down Compiler Compiler (TMG)
 Bottom up Compiler Compiler (YACC)
 Macro processor

19
 File System - Rooted
 Ordinary Files
 Directories
 Special Files
 Mountable File Systems
 Access Control
 Read, write, and execute permissions for the Owner and Other
users
 Set-uid bit
 Notion of a Super User

20
 File System – I/O calls
 Simple – no distinction between “random” and sequential I/O
Filep=open(name, flag)
n=read(filep,buffer,count)
n=write(filep,buffer,count)
location=seek(filep,base,offset)

21
 File System – Implementation
 Directory contains filename and pointer to the file i-number
 i-number is an index to the system table i-list
 The entry (i-node) contains the file description:
• Its owner
• Its protection bits
• The physical disk address for its contents
• Its size
• Time of last modification
• The number of links to the file
• Bits for directory, special file etc.
 Common Buffer Pool

22
 Processes and Images
 processid = fork()
Splits into two independent processes
Program can test the return value to identify child or parent
 execute (file, arg1, arg2, …., argn)
 processid = wait()
 Exit(status)

23
 Processes, Images, Pipes
 processid = fork()
Splits into two independent processes
Program can test the return value to identify child or parent
 execute (file, arg1, arg2, …., argn)
 Exit(status)
 Filep = pipe() interprocess channel - filedescriptor

24
 The Shell
 Command arg1, arg2, … , argn)
 Standard I/O and file redirection
 stdin, stdout, stderr (file descriptors 0, 1 and 2)
 ed <script
 Filters e.g. ls | pr -2 | opr
 Multitasking
 Shell itself as a command
 Init

25
 Perspective
 Success of UNIX attributed to the fact that it was not designed
to meet any predefined objective
 Three considerations
 A system to make it easy to write, test, and run programs
 Made under sever size constraint – economy but also elegance
 The system maintains itself – all source code etc. available to early
users.

26
Unix Critcs and Detractors
 The UNIX-Hater’s Handbook
Edited by
Simson Garfinkel, Daniel Weise,and Steven Strassmann
http://web.mit.edu/~simsong/www/ugh.pdf

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 Portable OS and Standard OS
 Networking and Internet
 Itself not “open source” or “public domain” -
yet laid the seed
 GNU – Richard Stallman
 Minix – Tanenbaum
 Linux – Linus Trovalds
 Android and other mobile operating systems
Impacts

28
Video: Dennis Ritchie - Write in C
http://www.youtube.com/watch?v=H4YRPdRXKFs
Duration: 4 mins

2929
Thank You
Persistent Systems Limited
www.persistentsys.com

Life and Work of Ken Thompson and Dennis Ritchie | Turing Techtalk

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Life and Work of Ken Thompson and Dennis Ritchie | Turing Techtalk