Is this true?Is this true?

Nothing has really changedNothing has really changed in computer design since in computer design since Von Neumann Von Neumann

Early Computer ArchitectureEarly Computer Architecture

Accumulator-a set of Accumulator-a set of circuits to hold numeric circuits to hold numeric values and do values and do rudimentary arithmeticrudimentary arithmetic

Register-general Register-general temporary storagetemporary storage

Program counter-stored Program counter-stored location of the program location of the program instructions to be instructions to be fetched and executedfetched and executed

Word LengthWord Length Scientific work- 7 to 12 decimal digits, 30 Scientific work- 7 to 12 decimal digits, 30

to 50 bitsto 50 bits Business applications- seldom over 6 Business applications- seldom over 6

digits with 2 digits to the right of the digits with 2 digits to the right of the decimaldecimal

RCA 301RCA 301 IBM 1401-CPUIBM 1401-CPU IBM 702 IBM 702

The Labor Of ProgrammingThe Labor Of Programming

Programming has always been hardProgramming has always been hard

In the early days of large-scale In the early days of large-scale digital computers, it was labor-digital computers, it was labor-intensiveintensive

Hard to appreciate now, how much Hard to appreciate now, how much tedious work was involved thentedious work was involved then

The Early Beginnings of The Early Beginnings of SoftwareSoftware

Grace Hopper using the Grace Hopper using the Mark 1Mark 1a) coefficients of the arc tangent a) coefficients of the arc tangent seriesseriesb) lens design problemsb) lens design problems

Repetitive sequences had to Repetitive sequences had to be punched again and again be punched again and again into tapeinto tape

Compiler (A–0) “program Compiler (A–0) “program making routine”making routine” using subroutines using subroutines stored in librariesstored in libraries coder

Wish ListWish ListFloating 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 Wish list continuedcontinued

Mark III – Howard AikenMark III – Howard Aiken

Ambros Speiser

Mark III had a keyboard Mark III had a keyboard to record instructions in to record instructions in ordinary algebraic ordinary algebraic notation on magnetic notation on magnetic tapetape

The Machine itself The Machine itself translated it into code translated it into code that it could executethat it could execute

This device unnecessary This device unnecessary with a stored programwith a stored program

John John Backus Backus Born in Philadelphia, 1924Born in Philadelphia, 1924

Wealthy family, bad Wealthy family, bad studentstudent

Studied chemistry some, Studied chemistry some, medicine a little, math a lotmedicine a little, math a lot

Went to work for IBM, 1949Went to work for IBM, 1949

First job - calculate First job - calculate positions of the Moon positions of the Moon

IBM model SSEC 1948IBM model SSEC 1948no memory for no memory for software storagesoftware storage

programs entered programs entered on punched paper on punched paper tapetape

thousands of thousands of electro- electro- mechanical parts mechanical parts a) unreliable unreliableb)b) slow slow

SSelective elective SSequence equence EElectronic lectronic CCalculatoralculator

SSECSSEC

Desk Control

tape

Tape Drive

IBM model SSECIBM model SSEC

IBM model IBM model SSECSSEC

Floor Plan

SpeedcodiSpeedcodingng

proto-Fortranproto-FortranFor the IBM 701For the IBM 701 fixed-pointfixed-point single-address computersingle-address computer no index registersno index registers

Speedcoding made it look like a Speedcoding made it look like a 1.1. floating-point floating-point 2.2. free-address computer free-address computer 3.3. with index registers with index registers

No more binary codeNo more binary code

It ran a lot slower because it had to do all the extra It ran a lot slower because it had to do all the extra work of simulating floating-point and index work of simulating floating-point and index registers registers

BackusBackus

FORTRAN FORTRAN FORFORmula mula TRANTRANslating Systemslating System

19541954

The first popular high-The first popular high-level programming level programming languagelanguage

FORTRANFORTRAN

A team led by John Backus at IBMA team led by John Backus at IBM

– supposed to take six months -- took two supposed to take six months -- took two yearsyears

– supposed to eliminate coding errors supposed to eliminate coding errors and debuggingand debugging

– supposed to generate efficient code, supposed to generate efficient code, comparable with hand-written code -- comparable with hand-written code -- very successful at thisvery successful at this

– closely tied to the IBM 704 architectureclosely tied to the IBM 704 architecture

COBOL COBOL 19601960CCommon ommon BBusiness usiness OOriented riented

LLanguageanguage

Produced by a committee:Produced by a committee:

Selden & Tierney - IBM Selden & Tierney - IBM Bromberg & Discount - RCABromberg & Discount - RCAReeves & Sammet -Reeves & Sammet -Sylvania Electric Sylvania Electric ProductsProducts

Able to use long character names that Able to use long character names that made the language look like ordinary made the language look like ordinary English English

COBOLCOBOL

FORTRANFORTRANIf A > BIf A > B

COBOLCOBOLIF EMPLOYEE-HOURS IS GREATER IF EMPLOYEE-HOURS IS GREATER

THAN MAXIMUM THAN MAXIMUM

COBOLCOBOL promoted by the US Department promoted by the US Department

of Defenseof Defense

for simple computations on large for simple computations on large amounts of dataamounts of data

introduced the record structureintroduced the record structure

most widely used programming most widely used programming language during the 1960s and language during the 1960s and 1970s1970s

MulticsMultics MultMultiplexed iplexed IInformation and nformation and

CComputing omputing SServiceervice time-sharing operating system co-time-sharing operating system co-

designed by a consortium including designed by a consortium including MIT, GE and Bell LaboratoriesMIT, GE and Bell Laboratories

first major OS to run on a symmetric first major OS to run on a symmetric multiprocessormultiprocessor

provided a hierarchical file system provided a hierarchical file system with access control on individual fileswith access control on individual files

Segmented memory Segmented memory

Virtual memory Virtual memory

High-level language implementation High-level language implementation

Shared memory multiprocessor Shared memory multiprocessor

Multi-language support Multi-language support

Relational database Relational database

Security Security

Multics Multics featuresfeatures

MulticMulticss On-line reconfiguration On-line reconfiguration

Software engineeringSoftware engineering written in PL/Iwritten in PL/IHoneywell commercialized MulticsHoneywell commercialized Multics

in 1972 in 1972

3 Multicians in 19783 Multicians in 1978

Myths about MulticsMyths about Multics Myth: Multics failed in 1969 when Bell Labs quit. Myth: Multics failed in 1969 when Bell Labs quit.

Multics survivedMultics survived. .

Myth: Multics failed. Myth: Multics failed. Multics met its goals.Multics met its goals.

Myth: Unix was operational before Multics. Myth: Unix was operational before Multics. False.False.

Myth: Multics was big and slow. Myth: Multics was big and slow. True at first.True at first.

Myth: Multics was vastly expensive. Myth: Multics was vastly expensive. You get You get what you pay for.what you pay for.

Myth: Ken Thompson wrote Multics. Myth: Ken Thompson wrote Multics. Ken was Ken was one of many. one of many.

More Myths about More Myths about MulticsMultics

Myth: Multics was built by the waterfall method Myth: Multics was built by the waterfall method Closer to spiral method.Closer to spiral method.

Myth: Multics was closed source Myth: Multics was closed source It was shipped It was shipped with source for many years.with source for many years.

Myth: Multics was designed with military Myth: Multics was designed with military security in mind. security in mind. Separate project.Separate project.

Myth: You had to give a password to log out. Myth: You had to give a password to log out. User app, terminal locker.User app, terminal locker.

Myth: Multics error messages were in Latin. Myth: Multics error messages were in Latin. One One was.was.

UnixUnix (first UNICS)(first UNICS) Bell LabsBell Labs

Developed on Digital Developed on Digital Equipment Corp. PDP – Equipment Corp. PDP – 7 and then PDP – 117 and then PDP – 11

Added a text formatting Added a text formatting program called “roff” program called “roff” and a text editor written and a text editor written in assembly codein assembly code

In 1973, re-written in In 1973, re-written in the C programming the C programming language language

Ken Thompson & Dennis Ritchie

C Developed in early 1970’sDeveloped in early 1970’s

Low-level minimalist Low-level minimalist standardized programming standardized programming languagelanguage

Efficient, popular Efficient, popular programming language for programming language for writing system softwarewriting system software

Ken Thompson

Dennis Ritchie

CCeasier to write large programs with easier to write large programs with

fewer errors in the procedural fewer errors in the procedural programming paradigmprogramming paradigm

Compilers, libraries, and interpreters Compilers, libraries, and interpreters of other higher-level languages are of other higher-level languages are often implemented in C often implemented in C

Two failed languagesTwo failed languages

Algol-68Algol-68 From Algol-60From Algol-60 Too complexToo complex Hard to understandHard to understand Lead to PascalLead to Pascal

PL/IPL/I To replace FORTRAN and To replace FORTRAN and

COBOLCOBOL Complexity overwhelmed Complexity overwhelmed

its advantages its advantages Release date killed itRelease date killed it

The Birth of Computer ScienceThe Birth of Computer Science

First taught in: 1) Mathematics 2) Electrical Engineering

StanfordStanford

PerduePerdue

Computer ScientistsComputer Scientists

Who Who areare these guys ! ? these guys ! ?