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

The History of Computers About me What I’ll be talking about Primarily information on selected computers from the 1930s - 1950s 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

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

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

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

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

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”

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

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

Digital / Mechanical Computers 1800’s & 1930’s

Digital / Mechanical Babbage Difference & Analytical Engines Charles Babbage, 1791 - 1871 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

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

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

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

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

Digital / Mechanical Babbage Difference & Analytical Engines Difference Engine #2, 1847 - 1849 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 1985 - 2002, using Babbage’s original designs Video…

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

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

Digital / Mechanical Zuse Z1 Konrad Zuse, Germany, 1910 - 1995 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. 1943 during WW II Berlin bombardment Reconstructed Z1, 1986 - 1989

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

Digital / Mechanical Zuse Z1 Input Output Clock

Digital / Mechanical Zuse Z1 Input Output Clock

Digital / Mechanical Zuse Z1 Input Output Clock

Digital / Mechanical Zuse Z1 Input Output Clock

Digital / Mechanical Zuse Z1 Input Output Clock

Digital / Mechanical Zuse Z1 Input Output Clock

Analog / Mechanical Computers Early 1900s

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

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

Analog / Mechanical Bush Differential Analyzer

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

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

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

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

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

Analog / Mechanical Bush Differential Analyzer

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…

Digital / Electric (Relay) Computers 1930s - 1940s

Digital / Electric - Relay Bell Relay Computers Bell Labs / George Stibitz 1937 – Demonstrate relays used as a binary adder 1939 - 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

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

Digital / Electric - Relay Zuse Z3 Reconstructed Z3, 1960

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

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

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

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

Digital / Electronic (Tube) Computers 1940s - 1950s

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

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

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!)

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

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

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

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 5,000 10-digit additions / sec 333 multiplications / sec Calculate trajectory in 20 seconds (D.A. took 15-30 minutes)

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

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

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

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…

Digital / Electronic (Tube) ENIAC

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 1,024 44-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

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

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

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

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

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

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

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

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

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

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?

Analog / Electronic (Transistor) Computers 1950s - 1960s

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.

Hobby / Training Computers 1950s - 1960s

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)

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

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

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

The End Thanks!

Resources Websites Books Computer History Museum London Science Museum http://www.computerhistory.org Mountain View, CA London Science Museum http://www.sciencemuseum.org.uk/ Tim Robinson’s Differential Analyzer - Meccano http://www.meccano.us/differential_analyzers/robinson_da/ 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