Unit One-Computer Overview
Section A About Computer
Computer science is the discilpline that seeks to build a scientific foundation for
such topics as computer
design ,computer programming,information processing,algorithmic solutions of problems,and the
algormation
solutions of problems,and the algorithmic process itself.It provides the
underpinnings for today's computer
applications as well as the foundations for tomorrow's computing infrastructure.
1.History
Abacus:Today's computers have an extensive genealogy.One of the earlier
computing devices was the abacus.It
most likely had its roots in ancient China and was used in the early Greek and Roman civilizations.
The machine is quit simple ,consisting of beads strung on rods that are in turn mounted
in a rectangular frame.
As the beads are moved back and forth in the rods,their positions represent stored
values.It is in the
position of the beads that this"computer"represents and stores data.For control of an algorithm's
execution,the machine relies on the human operator.Thus the abacus alone is
merely a
data storage system.
Adding Machine:After the Middle Ages and before the Modern Era the quest for
more sophisticated computing
machines was seeded.A few inventors began to experiment with the technology of gears.
Among these were Blaise
Pascal of France,Gottfried Wilhelm Leibniz of Germany,and Charles Bannage of
England.
The first adding machine,a precursor of the digital computer,was devised in 1642 by
Blaise Pascal.This device employed a series of
ten-toothed wheels,each representing a dight from 0 to 9,with data being input mechanically
by establishinginitial gear positions.Output was achieved by observing the final gear positions.
Analytical Engine:In the 19th century,the Brish mathematically and inventor
Charles Babbage conceived the
Difference Engine(of which only a demonstration model was construed)could
be modified to perform a variety
of calculations,but his Analytical Engine was designed to read instructions
in the form of holes in paper
cards.Thus Babbage's Analytical Engine was programmable.
In fact,Augusta Ada Byron,who published a paper in
which she demonstrated how Babbage's Analytical Engine could be programmed to perform various
computations,is often identified today as the world's first programmer.
Electronic Computers:The technology of the time was unable to produce the complex geardriven
machines ofPascal,Leibniz,and Babbage in a financially feasible manner,But with the advance
in electronics in theearly 1900s,this barrier was overcome.Some researchers were applying the
technology of vacuum tubes to
construct totally electronic computers.The first of these machines was apparerntly the
Atanasoff-Berry machine,comstructed during the period from 1937 to 1941 at Iowa State College by
John Atanasoff and his
assistant,Clifford Berry.Another was a machine called Colossus,used
by the team headed by Alan Turing
to decode German messages during the latter part of World War Two.
Other,more flecible machines,such as the ENIAC developed.