CS101 - CS101 Chapter 6-History of Computers History of...

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CS101 Chapter 6-History of Computers History of Computer o First computers just tallied items, such as counting on our fingers o Pebbles were very popular 40,000 years ago to do simple arithmetic o Stonehenge- used to calculate celestial events -2500BCE o Abacus- Chinese calculator – 3000 BCE o Mechanical devices 1642- Pascal built mechanical calculation machine Used mechanical gears, hand crank, dials and knobs, Other machines followed 1805- first programmable device- Jacquards Loom Wove tapestries with elaborate programmable patters Pattern represented by metal punch cards fed into loom Using loom it became possible to mass produce tapestries and even reprogram it to produce different patters simply by changing cards Mid 1800s- Babbage designed analytical engine Design expanded upon mechanical calculators but programmable via punch cards Described general layout of modern computers Never completed functional machine- design beyond technology of the day 1930s- several engineers independently built computers using electromagnetic relays Physical switch which can be opened closed via electrical current Relays used extensively in early telephone exchanges Zuse(Nazi Germany)- his machines were destroyed in WWII Atanasoff (Iowa state)- built partially working machine with grad student Stibitz (bell labs)- built MARK I Computer that followed design of babbage o Limited capacities Mid 1940s- vacuum tubes replaced relays o Light bulb containing partial vacuum to speed electron flow o Could control flow of electricity faster than relays since they had no moving parts o Invented by Lee de Forest in 1906 1940s- hybrid computers using vacuum tubes and relays built o Colossus- first electronic computer designed by Alan Turing Used to decode nazi communications o ENIAC- electronic computer with 18,000 vacuum tubes and 1,500 relays Weighed 30 tons, consumed 140 kwatts o Were not general purpose computers o Could enter input using dials and knobs, paper tape o Needed to reconfigure to perform different computation Von Neumann popularized idea of stored program computer o Memory stores both data and programs o Central process unit CPU executes by loading program instructions from memory and executing them in sequence o Input/output device allow for interaction with user o Virtually all modern machines follow this architecture 1950s- transistors replaced tubes
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o Transistor is a piece of silicon whose conductivity can be turned on and off using electric current o Performed same switching function of vacuum tubes but were smaller faster more reliable and cheaper to mass produce o Invented by Bardeen, Brattain, and Shockley in 1948 o Claimed to be most important invention of 20 th century Late 1950s- High level languages designed to make programming more natural as commercial use became widespread o FORTRAN, LISP, BASIC, COBOL, Eckert-Mauchly, DEC o Grace Hopper was on the team that found the first computer bug o
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