Definition of a Computer
Simplest definition of a computer: A device that processes input and generates output

Key words:

Modern Computers are electronic, complex, and interactive, but can be reduced to simple input-output processing devices


History of Computers: 3000 BC to Present

History of Computers - Long, Long Ago
The Abacus

  • beads on rods to count and calculate
  • still widely used in Asia!


History of Computers - Way Back When
The Slide Rule 1630

  • based on Napier’s rules for logarithms
  • used until 1970s


History of Computers - 19th Century
Jacquard Loom

  • used metal cards with punched holes to guide weaving process
  • first stored program - metal cards
  • first computer manufacturing
  • still in use today!


Charles Babbage - 1792-1871
Difference Engine c.1822

  • huge calculator, never finished
Analytical Engine 1833
  • could store numbers
  • calculating "mill" used punched metal cards for instructions
  • powered by steam!
  • accurate to six decimal places
Babbage's Analytical Engine

Ada Augusta - First Programmer

Discussion Question

Vacuum Tubes - 1930 - 1950s

  • First Generation Electronic Computers used Vacuum Tubes
  • Vacuum tubes are glass tubes with circuits inside.
  • Vacuum tubes have no air inside of them, which protects the circuitry.
UNIVAC - 1951
  • First commercially available computer
  • sold to censu bureau
  • "a big pocket calculator"
  • until 1970 was standard computer, but very expensive

Grace Hopper

  • Programmed UNIVAC
  • Recipient of Computer Science’s first "Man of the Year Award"

First Computer Bug - 1945

  • Relay cards carried information
  • Grace Hopper found an actual moth stuck to card responsible for a malfunction
  • Called it "debugging" a computer
First computer bug is a moth

First Transistor

  • Uses Silicon
  • developed in 1948
  • won a Nobel prize
  • on-off switch
  • Second Generation Computers used Transistors, starting in 1956

Integrated Circuits

  • Third Generation Computers used Integrated Circuits (chips).
  • Integrated Circuits are transistors, resistors, and capacitors integrated together into a single “chip”


Birth of Personal Computers -

Kenbak I - 1971

  • Very primitive, just flashing lights and buttons
  • about $750

MITS Altair - 1975 (pictured)

  • 256 byte memory
  • 2 MHz Intel 8080 chips
  • Just a box with flashing lights
  • cost $395 kit, $495 assembled.


The First Microprocessor - 1971

Inside the Intel 4004 Microchip - 2250 Transistors
Inside the Intel 4004 - 2250 Transistors

Generations of Electronic Computers
Generation First



Second Gen.


Third Gen.


Fourth Gen.


Technology Vacuum Tubes Transistors Integrated Circuits (multiple transistors) Microchips (millions of transistors)
Size Filled Whole Buildings Filled half a room Smaller Tiny - Palm Pilot is as powerful as old building sized computer


Over the past 50 years, the Electronic Computer has evolved rapidly.

IBM PC - 1981

Apple Computers

1990s: Pentiums and Power Macs


How Electronic Computers Have Progressed


(1968 vers.)

Kenbak 1






Pentium III
Circuits Tubes,

Transistors, Integrated Circuits*

130 Integrated Circuits Intel 8088

Microchip - 29,000 Transistors

Motorola 68000  Intel P-III

Microchip - 7.5 million transistors

Generation I-II-III* III IV IV IV
RAM Memory 512 K 265 Bytes 256 K 640 K 128 Mb
Speed 1.3 MHz 1 KHz 4.77 Mhz 8 MHz 1000 MHz
Storage 100 MB Hard Drive none Floppy Drive Floppy Drives Hard Drive, Floppy, CD-Rom
Size Whole Room Briefcase

(no monitor)

Briefcase + Monitor Two shoeboxes (integrated monitor) Small Tower
Cost $1.6 million $750 $1595 ~$4000 $1500

*Early UNIVACs had vacuum tubes, middle models had transistors, and by the end they used integrated circuits

What’s next for computers?