Unit 2 - Computer Architecture

The origin of computing is found far back in human history - the first time man responded to the need for a system of counting.  Even before the existence of formal symbols, objects such as stones or sticks were used to establish crude counting methods.  Stones and pebbles were placed on boards and used to represent amounts of money during bartering sessions.  In fact, the word "calculate" derives from the Greek word kalyx - which means "pebble" or "small stone".

Some noteworthy developments in computing devices throughout history include:
 

2700 B.C. to 1000 A.D.	The Abacus An "abacus" is a generic term which refers to a counting device using columns of beads.  Early versions of the abacus used organized groupings of pebbles and stones, and have been attributed to civilizations from ancient Sumeria, Babylon, Egypt, and Greece.  By the first century A.D., the Romans had created a portable device based on the number 5, which would correspond to the Roman Numeral system (also based on the number 5).  Later versions would appear in other cultures, probably due to trade relationships with the Roman Empire.  The most recognizable version is the Chinese "suanpan" (right).	Suanpan showing 203,746
1642	Pascal's Wheel French mathematician and physicist Blaise Pascal built the first mechanical calculating machine, called Pascal's Wheel, which was capable of adding and subtracting numbers.  The machine used a series of dials attached to geared wheels, which turned one revolution for each value of 10.  (This principle is still in use today - odometers in cars use Pascal's wheel principle to keep track of the number of kilometers traveled).	Pascal's Wheel
1725	Programmable Weaving Looms French weaver Basile Bouchon constructed a weaving loom that could be controlled by holes in a roll of paper.  The holes allowed some needles in the loom to be engaged, while others were held back.  The loom was therefore "programmed" by the placement of the holes in the roll of paper to produce a particular pattern!  (Up until this time, someone had to be employed to control the needles and decide which would be used for each line of weave in the fabric).  By 1800, French inventor Joseph-Marie Jacquard (1752-1834) had improved upon Bouchon's design by developing  a loom which used a punched card to control each line of the weave.  Over 1000 needles could be controlled at one time, and very intricate designs were easily created.	Napolean inspecting Jacquard's Loom
1834	The Analytical Engine Charles Babbage was a mathematics professor at Trinity College in Cambridge, England.  After several unsuccessful attempts at building a mechanical calculating machine, Babbage developed the analytical engine.  Babbages' designs were amazingly similar to the general design of modern-day computers, including a central arithmetic unit for calculating (called a mill), an area for retaining numbers (called a store), and sophisticated methods for input and output. While working on his analytical engine, Babbage began a lengthy correspondence with poet Lord Byron's daughtor, Ada Augusta, Countess of Lovelace.  Lady Lovelace became fascinated with Babbages ideas, and in her analysis of his analytical engine, she developed the essential ideas of programming, such as "branching" to perform decisions and repetitions.  Because of her work in this area, she is considered to be the first computer programmer!  (The programming language "Ada" is named after her).	Babbage's Analytical Engine
1890	The Hollerith Machine Dr. Herman Hollerith was a statistician and inventor who was hired by the U.S. Census Bureau to create a machine that could tabulate the 1890 census. Hollerith used Jacquard's punched-card idea to feed personal statistics into his machine.  Holes in the punched cards stood for a person's age, sex, state, and other similar information.  There was one card for each person.  As each card was fed into the machine, a set of metal pins were brought down on the card.  The pins passed through any holes punched in the card, which completed an electrical circuit which turned a counter dial.  Using Hollerith's machine, the 1890 census was tabulated in just two years (the 1880 census had taken eight years to tabulate!), which saved the U.S. Census Bureau millions of dollars. Hollerith eventually formed his own company In 1896, then later merged with several other companies to form the Computing Tabulating Recording company (CTR) in 1911, one of the first conglomerates in the USA.	The Hollerith Machine
1924	The Birth of IBM Although Herman Hollerith may have been a brilliant inventor, he was not a very good businessman.  He knew very little about marketing and sales, and refused to listen to ideas on how to improve the design of his machines.  Other companies were soon selling tabulating machines that performed better and cost less than CTRs.  In 1914, a young salesman named Thomas J. Watson Sr. joined CTR, which now had 1300 employees.  Watson began a running battle with Hollerith over the direction of the company.  When Hollerith retired in 1921, Watson assumed full control of CTR, and in 1924, was named president.  Shortly thereafter, Watson changed the name of the company to International Business Machines, or IBM.	Thomas J. Watson Sr.