Is this true? Nothing has really changed in computer design since Von Neumann Nothing has really changed in computer design since Von Neumann

Early Computer Architecture Accumulator-a set of circuits to hold numeric values and do rudimentary arithmetic Accumulator-a set of circuits to hold numeric values and do rudimentary arithmetic Register-general temporary storage Register-general temporary storage Program counter-stored location of the program instructions to be fetched and executed Program counter-stored location of the program instructions to be fetched and executed

Word Length Scientific work- 7 to 12 decimal digits, 30 to 50 bits Scientific work- 7 to 12 decimal digits, 30 to 50 bits Business applications- seldom over 6 digits with 2 digits to the right of the decimal Business applications- seldom over 6 digits with 2 digits to the right of the decimal RCA 301IBM 1401-CPU IBM 702

The Labor Of Programming Programming has always been hard Programming has always been hard In the early days of large-scale digital computers, it was labor- intensive In the early days of large-scale digital computers, it was labor- intensive Hard to appreciate now, how much tedious work was involved then Hard to appreciate now, how much tedious work was involved then

The Early Beginnings of Software Grace Hopper using the Mark 1 a) coefficients of the arc tangent series b) lens design problems Grace Hopper using the Mark 1 a) coefficients of the arc tangent series b) lens design problems Repetitive sequences had to be punched again and again into tape Repetitive sequences had to be punched again and again into tape Compiler (A–0) “program making routine” using subroutines stored in libraries Compiler (A–0) “program making routine” using subroutines stored in libraries coder

Wish List Floating point: coders had to keep track of the exponent manually (Babylonian style) Relative addressing: coders kept notebooks of subroutines, but the codes had to be adjusted by hand for the absolute addresses

Array subscripting help Something easier to remember than octal opcodes Wish list continued

Mark III – Howard Aiken Ambros Speiser Mark III had a keyboard to record instructions in ordinary algebraic notation on magnetic tape Mark III had a keyboard to record instructions in ordinary algebraic notation on magnetic tape The Machine itself translated it into code that it could execute The Machine itself translated it into code that it could execute This device unnecessary with a stored program This device unnecessary with a stored program

John Backus Born in Philadelphia, 1924 Born in Philadelphia, 1924 Wealthy family, bad student Wealthy family, bad student Studied chemistry some, medicine a little, math a lot Studied chemistry some, medicine a little, math a lot Went to work for IBM, 1949 Went to work for IBM, 1949 First job - calculate positions of the Moon First job - calculate positions of the Moon

IBM model SSEC 1948 no memory for software storage programs entered on punched paper tape thousands of electro- mechanical parts unreliable b) slow thousands of electro- mechanical parts a) unreliable b) slow Selective Sequence Electronic Calculator

SSEC Desk Control tape Tape Drive

IBM model SSEC

Floor Plan

Speedcoding proto-Fortran For the IBM 701 fixed-point fixed-point single-address computer single-address computer no index registers no index registers Speedcoding made it look like a 1. floating-point 2. free-address computer 1. floating-point 2. free-address computer 3. with index registers 3. with index registers No more binary code It ran a lot slower because it had to do all the extra work of simulating floating-point and index registers Backus

FORTRAN FORmula TRANslating System 1954 The first popular high-level programming language

FORTRAN A team led by John Backus at IBM –supposed to take six months -- took two years –supposed to eliminate coding errors and debugging –supposed to generate efficient code, comparable with hand-written code -- very successful at this –closely tied to the IBM 704 architecture

COBOL 1960 Common Business Oriented Language Produced by a committee: Selden & Tierney - IBM Bromberg & Discount - RCA Reeves & Sammet -Sylvania Electric Products Able to use long character names that made the language look like ordinary English

COBOL FORTRAN FORTRAN If A > B COBOL COBOL IF EMPLOYEE-HOURS IS GREATER THAN MAXIMUM

COBOL promoted by the US Department of Defense for simple computations on large amounts of data introduced the record structure most widely used programming language during the 1960s and 1970s

Multics Multiplexed Information and Computing Service time-sharing operating system co- designed by a consortium including MIT, GE and Bell Laboratories time-sharing operating system co- designed by a consortium including MIT, GE and Bell Laboratories first major OS to run on a symmetric multiprocessor first major OS to run on a symmetric multiprocessor provided a hierarchical file system with access control on individual files provided a hierarchical file system with access control on individual files

Segmented memory Virtual memory High-level language implementation Shared memory multiprocessor Multi-language support Relational database Security Multics features

Multics On-line reconfiguration On-line reconfiguration Software engineering Software engineering written in PL/I written in PL/I Honeywell commercialized Multics in 1972 Honeywell commercialized Multics in Multicians in 1978

Myths about Multics Myth: Multics failed in 1969 when Bell Labs quit. Multics survived. Myth: Multics failed in 1969 when Bell Labs quit. Multics survived. Myth: Multics failed. Multics met its goals. Myth: Multics failed. Multics met its goals. Myth: Unix was operational before Multics. False. Myth: Unix was operational before Multics. False. Myth: Multics was big and slow. True at first. Myth: Multics was big and slow. True at first. Myth: Multics was vastly expensive. You get what you pay for. Myth: Multics was vastly expensive. You get what you pay for. Myth: Ken Thompson wrote Multics. Ken was one of many. Myth: Ken Thompson wrote Multics. Ken was one of many.

More Myths about Multics Myth: Multics was built by the waterfall method Closer to spiral method. Myth: Multics was built by the waterfall method Closer to spiral method. Myth: Multics was closed source It was shipped with source for many years. Myth: Multics was closed source It was shipped with source for many years. Myth: Multics was designed with military security in mind. Separate project. Myth: Multics was designed with military security in mind. Separate project. Myth: You had to give a password to log out. User app, terminal locker. Myth: You had to give a password to log out. User app, terminal locker. Myth: Multics error messages were in Latin. One was. Myth: Multics error messages were in Latin. One was.

Unix (first UNICS) Bell Labs Bell Labs Developed on Digital Equipment Corp. PDP – 7 and then PDP – 11 Developed on Digital Equipment Corp. PDP – 7 and then PDP – 11 Added a text formatting program called “roff” and a text editor written in assembly code Added a text formatting program called “roff” and a text editor written in assembly code In 1973, re-written in the C programming language In 1973, re-written in the C programming language  Ken Thompson & Dennis Ritchie 

C Developed in early 1970’s Developed in early 1970’s Low-level minimalist standardized programming language Low-level minimalist standardized programming language Efficient, popular programming language for writing system software Efficient, popular programming language for writing system software Ken Thompson Dennis Ritchie

C easier to write large programs with fewer errors in the procedural programming paradigm easier to write large programs with fewer errors in the procedural programming paradigm Compilers, libraries, and interpreters of other higher-level languages are often implemented in C Compilers, libraries, and interpreters of other higher-level languages are often implemented in C

Two failed languages Algol-68 From Algol-60 From Algol-60 Too complex Too complex Hard to understand Hard to understand Lead to Pascal Lead to Pascal PL/I PL/I To replace FORTRAN and COBOL To replace FORTRAN and COBOL Complexity overwhelmed its advantages Complexity overwhelmed its advantages Release date killed it Release date killed it

The Birth of Computer Science First taught in: 1) Mathematics 2) Electrical Engineering

Stanford

Perdue

Computer Scientists Who are these guys ! ?