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A Brief Tour of The History of Computers

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1 A Brief Tour of The History of Computers
Presented by Kevin Nichols KA7OFR

2 The History of Computers
About me What I’ll be talking about Primarily information on selected computers from the 1930s s A few details of how specific computers worked Such a vast field, I can do no more than touch briefly on what’s out there

3 Preliminaries What is a computer?
A computer is “a machine that manipulates data according to a list of instructions” – Wikipedia A program historically distinguished computers from calculators, but not always Distinction is also made between devices that have conditional instructions and those that do not Early computers came in two flavors: Analog & Digital, And three methods of implementation: Mechanical, Electric & Electronic

4 Early Calculating Devices
Many examples of early calculating devices Abacus / Soroban Astrolabe Napier’s Bones Slide Rules

5 Early Calculating Devices
But none of these are computers if we adopt the definition that a computer is a device that contains a program, a list of instructions to carry out automatically What I will discuss today are early mechanical and electronic computers that have the ability to be programmed

6 “Computer” Side Note: The term “computer”, a term in use from the mid 17th century, meant a person who performed mathematical calculations (“computors”)

7 First Computer Which was the “first” computer? Highly controversial
Depends on specific terms and precise qualifications “First electronic computer with stored program memory” vs “First stored program computer” vs “First electronic computer” Not my intent to try to pin it down here I’ll just present several of the more “interesting” and historical computers, and leave it to you to research which you think was the “first”

8 Computer Categories Categorizing computers
Initially computers were human, then mechanical, then electric, and finally electronic Differentiated by the calculating “medium” used Mechanical Gears, shafts, pulleys Electrically operated Relays Electronic Vacuum tubes, Transistors, ICs Differentiated by the method of computing Analog was initially faster, but less accurate Digital was initially slower but more precise

9 Electronic (transistor/IC)
Computer Categories Mechanical Electrical Electronic (tube) Electronic (transistor/IC) Analog Digital Vannevar Bush’s Differential Analyzer Instructional computers (GE EF-140) Op-Amp Based Computers (Heathkit ES Serias) Op-Amp based “plugboard” computers Babbage’s Difference & Analytical Engines Zuse Z1 Bell Labs Relay Computers (Complex Number Calculator) Zuse Z3 Eniac Edvac Manchester “Baby” Edsac Modern Computers

10 Digital / Mechanical Computers
1800’s & 1930’s

11 Digital / Mechanical Babbage Difference & Analytical Engines
Charles Babbage, Work included design of two classes of machines Difference Engines Used method of finite differences Uses only addition & subtraction Analytical Engines Mechanized true “computer” Would have allowed decisions to be made based on previous results Decimal based machines None of his machines were ever completed in his lifetime Image courtesy Computer History museum, Mountain View CA

12 Digital / Mechanical Babbage Difference & Analytical Engines
In 1800’s, mathematical tables were used extensively for Astronomy, Engineering, Finance, insurance Tables were generated by hand and prone to errors These are what prompted Babbage to work on his mechanical devices Image courtesy Computer History museum, Mountain View CA

13 Digital / Mechanical Babbage Difference & Analytical Engines
Babbage utilized the method of “finite differences” to create the mathematical tables Eliminated the need for more complicated operations (multiplication, division) Easier to implement using mechanical devices

14 Digital / Mechanical Babbage Difference & Analytical Engines
Say we want to calculate the function F(x) = X^2 + 4 The first several values of the function are calculated (by hand) Columns of differences are calculated until they are constant The rest of the values of the function can then be calculated (without multiplication!) Any nth degree polynomial can be calculated starting with the nth difference That is what Babbage was trying to “mechanize” Image courtesy Computer History museum, Mountain View CA

15 Digital / Mechanical Babbage Difference & Analytical Engines
Difference Engine #1, 1821 25,000 parts Est. 15 tons 8 ft high Designed to calculate polynomial tables using method of finite differences Work was halted in 1832 due to dispute with a co-worker Image courtesy Computer History museum, Mountain View CA Portion of Difference Engine #1, 1832

16 Digital / Mechanical Babbage Difference & Analytical Engines
Difference Engine #2, 8,000 parts (3x less than #1) 5 tons 7ft high, 11 ft long, 18” deep Could compute 31 digit results Up to 7th order polynomial (could hold 7 differences) Included a paper printing press with mold for type Image courtesy Computer History museum, Mountain View CA Working reproduction of Difference Engine #2 Built from , using Babbage’s original designs Video…

17 Digital / Mechanical Babbage Difference & Analytical Engines
Video courtesy: Computer History Museum, Mountain View CA

18 Digital / Mechanical Babbage Difference & Analytical Engines
Babbage also designed a much more ambitious calculating device: The Analytical Engine Contained a memory (the “store”) and an arithmetical unit (the “mill”) Could add, subtract, multiply & divide Was programmable using punched cards Capable of conditional branches and loops Image courtesy Science Museum, London England Portion of the “mill” of the Analytical Engine, 1871

19 Digital / Mechanical Zuse Z1
Konrad Zuse, Germany, Z1 built 1936 – 1938 in apartment of his parents Binary computer using metal plates as logic elements Programmed via punched tape 2 registers of 22 bits each Floating point numbers(!) Clock frequency of 1 Hz Destroyed in Dec during WW II Berlin bombardment Reconstructed Z1,

20 Digital / Mechanical Zuse Z1
Metal sheets function as logic gates AND OR NOT NOT OR Part of original metal plates, Z1

21 Digital / Mechanical Zuse Z1
Input Output Clock

22 Digital / Mechanical Zuse Z1
Input Output Clock

23 Digital / Mechanical Zuse Z1
Input Output Clock

24 Digital / Mechanical Zuse Z1
Input Output Clock

25 Digital / Mechanical Zuse Z1
Input Output Clock

26 Digital / Mechanical Zuse Z1
Input Output Clock

27 Analog / Mechanical Computers
Early 1900s

28 Analog / Mechanical Bush Differential Analyzer
Vannevar Bush, 1890 – 1974 Engineering professor at MIT Built the Differential Analyzer, 1928 – 1931 to solve electric power transmission problems Used metal rods, gears, wheels Designed to solve up to 6th order differential equations & calculate up to 18 independent variables Solves differential equations by integration, 2% accuracy 150 motors

29 Analog / Mechanical Bush Differential Analyzer
The Differential Analyzer consists of several interconnected parts Disk & Plate Integrators Torque Amplifiers Input/Output tables All the connecting gearing, rods, etc. Great effort required to set up the computer for different problems

30 Analog / Mechanical Bush Differential Analyzer

31 Analog / Mechanical Bush Differential Analyzer
Integration performed with glass disk integrators Uses knife edge wheel rolling on glass disk Rotation of output shaft depends on rotation of input glass disk, and distance of wheel from center of disk

32 Analog / Mechanical Bush Differential Analyzer
Torq Amplifier Required due to the very low torque output available from the integrator wheel Wheel must not be allowed to slip on glass disk Output rotates at same velocity as input, but with greatly increased torque

33 Analog / Mechanical Bush Differential Analyzer
Input/Output Tables Input table Provide arbitrary input as computer runs Computer drives ‘X’ direction, human turns knob to make pen follow curve Output table Computer drives pen in ‘X’ and ‘Y’ coordinates to draw curve on paper

34 Analog / Mechanical Bush Differential Analyzer
Examples of use Calculation of firing tables for artillery used in WWII “Bouncing Bomb” by Barnes Wallis for attack on Ruhr Valley Hydro dams in WWII Height, length, number of bounces calculated based on changing parameters of: Bomb initial spin, Speed & height of aircraft, Weight of bomb Bomb shape influencing ballistic characteristics, Buoyancy in water River control studies Calculation of soil erosion based in changing parameters of Rate at which water falls on surfaces, resistance to flow by surface Speed of flow of water, Volume of water

35 Analog / Mechanical Bush Differential Analyzer
A “home made” differential analyzer was built in 1934 by Hartree & Porter Built at the University of Manchester Made primarily of Meccano parts Was actually used for military purposes Cost 20 pounds Said to have Achieved 2% accuracy

36 Analog / Mechanical Bush Differential Analyzer

37 Analog / Mechanical Bush Differential Analyzer
A modern version of the Meccano Differential Analyzer was recently built Designed, assembled and operated by Tim Robinson Shown at the Vintage Computer Festival in California Contains 4 wheel & disk integrators Video…


39 Digital / Electric (Relay) Computers
1930s s

40 Digital / Electric - Relay Bell Relay Computers
Bell Labs / George Stibitz 1937 – Demonstrate relays used as a binary adder Complex Number Calculator (Model 1 Relay Computer) Demonstrated Cost $20,000 450 telephone relays Calculated quotient of two 8-place complex numbers in 30 seconds A calculator Not truly a computer First demonstration of remote access

41 Digital / Electric - Relay Zuse Z3
Konrad Zuse created many other relay-based ‘Z’ machines beyond the Z1, Z3 probably the most famous Operational May 12, 1941 64 numbers of 22 bits each Floating point math “+”, “-”, “*”, “/” and square root 5.3 Hz, Addition 0.8 seconds, multiplication 3 seconds 2600 relays, 4kW, 1 ton I/O using punched tape No conditional jump Reconstructed Z3, 1960

42 Digital / Electric - Relay Zuse Z3
Reconstructed Z3, 1960

43 Digital / Electric - Relay IBM Relay Computers
IBM / Harvard Mark I (Automatic Sequence Controlled Calculator) Development lead by Howard Aiken 1944 – Installed at Harvard University 51 ft long, weighed 5 tons 750,000 parts 72 accumulators, 60 sets of rotary switches Addition: 1/3 second, multiplication 1 second

44 Digital / Electric - Relay IBM Relay Computers
Automatic Sequence Controlled Calculator

45 Digital / Electric - Relay IBM Relay Computers
IBMs Selective Sequence Electronic Calculator 1948 – 1952 21,400 relays, 12,500 vacuum tubes 50 14 digit x 14 digit multiplications / sec Reportedly produced the moon position tables used for plotting the course of the 1969 Apollo moon flight

46 Digital / Electric - Relay IBM Relay Computers
Operator console Lots of blinking lights Machines of this era responsible for Hollywoods early fascination with blinking lights on computers

47 Digital / Electronic (Tube) Computers
1940s s

48 Digital / Electronic (Tube) ENIAC
At start of WWII, the Army’s Ballistics Research Lab trained about 100 human computers to calculate ballistics tables

49 Digital / Electronic (Tube) ENIAC
The Differential Analyzer & mechanical desktop calculators were used to solve the differential equations of motion A skilled operator took about 3 days to calculate a single trajectory As the war progressed, the BRL couldn’t keep up and fell way behind No firing table = useless guns! This crisis lead to the Army investing in two men with an idea of how to calculate much faster

50 Digital / Electronic -Tube ENIAC
Electronic Numerical Integrator And Computer Probably most well known of the early computers Started in April 1943 finished Nov 1945 (after the war!)

51 Digital / Electronic (Tube) ENIAC
Developed by John Mauchly and J. Presper Eckert Built at the Moore School of Electrical Engineering at the University of Pennsylvania

52 Digital / Electronic (Tube) ENIAC
The complete computer consisted of several interconnected modules Initiating Unit Master Programmer Cycling unit Multiplier Divider/Square Rooter 20 accumulators Input/Output Constant transmitters Function Tables

53 Digital / Electronic (Tube) ENIAC
Eniac used approx. 18,000 radio tubes Experts questioned reliability of tubes Eckert’s design for low power, modular design worked well

54 Digital / Electronic (Tube) ENIAC
ENIAC Statistics 17,468 tubes 70,000 resistors, 10,000 capacitors 1,500 relays 6,000 manual switches 8’ high x 80’ long, weighed 30 tons Consumed 174,000 watts Performance Could do 5, digit additions / sec 333 multiplications / sec Calculate trajectory in 20 seconds (D.A. took minutes)

55 Digital / Electronic (Tube) ENIAC
Computed by counting pulses using base-10 rather than base-2 Eniac’s primary calculating modules were the 20 Accumulators Each accumulator consisted of 10 ring counters of 10 digits each

56 Digital / Electronic (Tube) ENIAC
Function tables were (laboriously) entered using rotary switches

57 Digital / Electronic (Tube) ENIAC
Programming consisted of connecting together the various units with cables ENIAC could not store programs electronically A program was defined by the state of patch cords and switches “Reprogramming” required days of configuring cables

58 Digital / Electronic -Tube ENIAC
Eniac was even used as a recruiting tool Army’s 1940’s version of “Be all you can be” ad! Video…

59 Digital / Electronic (Tube) ENIAC

60 Digital / Electronic (Tube) EDVAC
Electronic Discrete Variable Automatic Computer Mauchly & Eckert proposed & started before Eniac was fully complete First designed computer for Stored Program concept Built for US Army Ballistics Research Lab. Contract signed April 1946, completed 1953 Contract for $100,000. Final cost $500,000 Capability 16 instructions 1, bit binary words Add (864 us), Subtract, Multiply (2.9 ms) Divide “RAM” was ultrasonic delay line 6,000 tubes, 12,000 diodes 56 kW power 8.5 tons

61 Digital / Electronic (Tube) EDVAC
Mercury delay lines used as “RAM” memory Leveraged research in RADAR during WWII 2 sets of 64 delay lines of 8 words capacity each Each tube was 384 us “long” Representative Univac delay line memory

62 Digital / Electronic (Tube) EDVAC
One of the first machine to which the “von Neumann Architecture” applies

63 Digital / Electronic (Tube) EDVAC
Eckert & Mauchly left the EDVAC project prior to completion, so it was not the first computer to operate with a stored program The Manchester “Baby” computer (above) therefore was the first computer to operate with the stored-program concept in June 1948

64 Digital / Electronic (Tube) Manchester Baby
Developed by Tom Kilburn at the University of Manchester Utilized a “Williams Tube” CRT for memory Stored 2048 bits of “RAM” 32 bit word length 3 bits for instructions Serial binary operation Solved finding the largest factor of 2^18 in 52 minutes

65 Digital / Electronic (Tube) Manchester Baby
RAM Memory was Williams Tube stores bits as charge on the face of the 6” CRT

66 Digital / Electronic (Tube) Manchester Baby
7 Instructions A = -S (010) A = A – S (101) S = A (110) If A < 0, CI = CI + 1 (011) CI = S (000) CI = CI + S (100) Halt (111) Later added: A=S, A=A + S, A = A & S Where A is the accumulator S address of a memory location CI is the address of the current instruction Tom Kilburn’s First Program, find the highest proper factor of any number

67 Digital / Electronic (Tube) EDSAC
Electronic Delay Storage Automatic Calculator EDSAC was developed by Maurice Wilkes at Cambridge University Work started in 1947 after Wilkes attended the 1946 Moore School lectures Patterned after EDVAC Contained 3000 tubes, 600 operations / sec First program executed May 1949

68 Digital / Electronic (Tube) EDSAC
EDSAC Memory EDSAC utilized ultrasonic mercury delay line tubes for its memory 32 tanks, each of which contained 32 numbers of 17 bits each (1024 storage locations) Two can be combined to handle a number 35 bits long

69 Digital / Electronic (Tube) EDSAC
Control Desk Contained 6 CRTs used to monitor the contents of memory 5-hole punched tape for input Output was to a teleprinter Used a telephone-type dial to input single decimal digits

70 Digital / Electronic (Tube) EDSAC
A very good Windows simulator is available for the EDSAC Written at Warwick university Complete instructions on use and sample programs are included Demonstration?

71 Analog / Electronic (Transistor) Computers
1950s s

72 Analog / Electronic (Transistor / IC)
In the 50s and 60s (even 70’s) electronic versions of the analog computer were available Generally consisted of Op Amps with the ability to connect them to add, subtract, multiply integrate, etc.

73 Hobby / Training Computers
1950s s

74 Hobby / Training computers
Heathkit produced several analog computer kits in the 50’s One shown is the ES series Tube operated, amplifier based 15 amplifiers, 3 I.C. power supplies, 30 coefficient potentiometers Full kit listed for $945 in 1956 (about $7,400 today)

75 Hobby / Training computers
GE produced a simple educational analog computer Model EF-140 shown Used potentiometers and cardboard dials with scale markings Solved equations like Y = 3X, or Z = X / Y $29.29, used 4 ‘D’ batteries Used transistors for amplifier / oscillator / null indicator

76 Hobby / Training computers
Digicomp 1 Produced in 1965 by ESR Inc. for $5.95 (about $40 today) Taught basics of boolean algebra, writing “programs”, binary addition Possible to play game of “nim” 50 page instruction manual included

77 Hobby / Training computers
Bell Labs “Cardiac” probably the least expensive of any “computer” Manually operated Designed to teach the basics of digital computer operation

78 The End Thanks!

79 Resources Websites Books Computer History Museum London Science Museum
Mountain View, CA London Science Museum Tim Robinson’s Differential Analyzer - Meccano Books “Bit by Bit an Illustrated History of Computers” by Stan Augarten “The Moore School Lectures” Vol 9, The MIT Press, © 1985 “The Origins of Digital Computers” Selected Papers, Springer Verlag, 2nd ed © 1970

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