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ENIAC

• First fully-electronic, general-purpose programmable computer

• Built 1943-1946

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Background History

• Artillery gun "firing tables"• Computed by hand• "Computers" were people

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Background History

• Herman Goldstine- Army lieutenant in charge of firing tables

• John Mauchly and Presper Eckert- Professors at U. of Pennsylvania- Idea for electronic calculating machines

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Background History

• Army accepts proposal!- Why?

Wartime desperation? Humiliation from atom bomb experience? New application of existing technology?

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Background History

• Built it in-place on first floor of engineering building on U.Penn campus

• University assigns 12 people to project- no senior faculty

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ENIAC Design

• Three main parts:- Math units- Memory units- “Master programmer”

• Wired together via cables

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ENIAC Design

• Twenty "accumulators"- Base 10, not base 2- Each could hold a 10-digit signed number- Each digit had its own circuit

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ENIAC Design

• Counters- Vacuum tubes, not electromechanical relays- 10 flip-flops per digit

each flip-flop consists of 2 vacuum tubes

- Converted electronic "pulses" to numbers- "Carry pulse" if sum > 9

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ENIAC Design

• Speed- 5000 additions per second- Multiplication: 2.6 milleseconds- Square root: 25 milleseconds

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ENIAC Design

• Hackery- Multiplication = lots of additions

"Multiplication table" had hard-coded answers to many multiplications

- Division & square roots = lots of subtractions and additions

- Constants: entered via "function tables" or punched cards

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ENIAC Design

• Output- Punched cards- Neon lightbulbs

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ENIAC Design

• Physical dimensions- 40 "panels"- each panel 8.5 feet tall (2.6 m)- 17,468 vacuum tubes- 30 tons

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ENIAC Design

• Quality standards- Used best vacuum tubes available

< 10% recommended voltage Always powered on Broken tubes once every 2 days

- "Least appetizing" wires- Custom-designed knobs

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Pictures

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Pictures

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Pictures

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Pictures

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Programming

• No "programming" in the modern sense of the word.

• Manually set dials and plug in cables

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Programming

• Time to program- Month to prepare a program- 2 days to set up a program- 1 week to debug

• “Usability” was an afterthought!

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Timeline

• Finally finished in 1946- (World War II was already over!)- Dismantled and sent to Aberdeen Proving

Ground (Maryland)

• Used for hydrogen bomb calculations

• Retired in 1955

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Demo

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Other Early Computers

• Konrad Zuse- Another early pioneer- Z1 (mechanical)- Z3 (electromechanical)- Z4 (electronic)

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Other Early Computers

• Atanasoff-Berry Computer (ABC)- 1937- All-electronic- Not general-purpose

Designed to solve linear equations

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Patent Problems

• ENIAC patent 1964• Honeywell vs Sperry-Rand (1973)

- invalidated patent- ABC declared first computer- computers are public domain

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Please note...

• Today is last of "pre-history"• Wednesday we start with the textbook

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“Test Question”

• On a scrap of paper, write a question that encapsulates one of the points from today's class, and turn it in.

• (Put your name on it!)