1. James Tam The history of computers and computing: Part II The computers of the 20 th century and the people behind those machines.

2. James Tam Konrad Zuse Developed a series of mechanical calculating machines (Z1, Z2, Z3, Z4). He was the first person to construct a calculator that could run automatically

3. James Tam The Bell Complex Number Calculator The Bell Computer could add, subtract, multiply and divide complex numbers Employed simple switches and flash bulbs

4. James Tam The Bell Complex Number Calculator (continued) It was the first machine to: handle multiple terminals be operated remotely Photos courtesy of Bell Technologies Inc.

5. James Tam The Bell Complex Number Calculator (continued) The computer used it’s own form of binary, Binary Coded Decimal (BCD). Decimal valueBCD value 00011 10100 20101 30110 40111 51000 61001 71010 81011 91100

6. James Tam The Harvard Mark I Manufactured by IBM and was donated to Harvard University. Extremely accurate Used by the U.S. navy (bureau of ordinance) Frequently used as a design model in subsequent machines.

7. James Tam John Atanasoff, Clifford Berry, and the ABC (Atanasoff-Berry Computer) Atanasoff needed a computer to perform specialized calculations He got his inspiration for the ABC in a bar. A photo of Clifford Berry and the ABC, courtesy of Dr. Atanasoff

8. James Tam The ENIAC Developed for the U.S. army at the Moore School of Electrical Engineering (University of Pennsylvania) Picture from the History of Computing Technology by Michael R. Williams

9. James Tam The ENIAC (continued) Used vacuum tubes to store information It was huge, complex and extremely expensive All this could store one digit!

10. James Tam Alan Turing A British Mathematician He worked at Bletchley Park as a code-breaker (contributed to the design of the machinery as well as applying his Mathematical knowledge) An Enigma encoding machine Pictures from the History of Computing Technology by Michael R. Williams

11. James Tam The EDSAC (Electronic Delay Storage Automatic Calculator) The first reliable computer to actually incorporate memory (The first computer design conceived that incorporated memory was the EDVAC/Electronic Discrete Variable Arithmetic Computer but it was completed after the EDSAC). Picture from the History of Computing Technology by Michael R. Williams

12. James Tam EDSAC (continued) First demonstrated in 1949 (ran at 500,000 Hz / 0.5 MHz)! A spin-off of the EDSAC (called LEO / Lyons Electric Office) was the first computer to be used for commercial data processing.

13. James Tam The Stretch One of the first super computers Pictures from the History of Computing Technology by Michael R. Williams The whole “Stretch” Control panel for the Stretch

14. James Tam Summary Some of the more ground breaking computer systems and personalities of the 20 th century. Konrad Zuse and the “Z” series of computers. The Bell Complex Number Calculator The Harvard Mark I Atanasoff, Berry and the ABC The ENIAC Alan Turing The EDSAC The Stretch