Introduction to computer science dessalegn Mequanint Yehuala Foreword

Pascal’s calculator
: Pascal’s calculator was the first true mechanical calculator. In 1642, at
the age of 19, the French philosopher and mathematician Blaise Pascal developed a rotating
wheel calculator, the predecessor of the latter popular desktop calculator.
The Difference Engine
: The difference engine is believed to be the forerunner of the
modern computer. Charles Babbage (1792-1871), a British mathematician and engineer, is
considered by many to be the real father of today’s computer was the developer of the
difference engine and designer of the analytical engine. He also designed a significantly
improved version of the difference engine (but not built) called Analytic engine. It has different
key components
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The store:
A memory wheel consisting of set of counter wheels
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The mill:
An arithmetic unit capable of performing the four basic arithmetic
operations. It operated on pairs of mechanical registers and produced a result
stored in another register, all of which were located in the store.
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Operation cards: 
These card selected one of the four arithmetic operations by
activating the mill to perform the selected function.
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Variable cards: 
These cards selected the memory locations to be used by the
mill for a particular operation ( a source of operand and the destination of the
result ).
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Output: 
was to print or a card punch device.
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Herman Hollerith’s Tabulating Machine
Herman Hollerith was a statistician, in 1880, he developed the tabulating machine
commissioned by the U.S. Census Bureau.

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Introduction To Computer Science
28
Mark I
: Developed by Howard Aiken at Harvard university in 1944, Mark I, was the first
electromechanical computer. Instructions were provided by means of punched paper
tape, which combined the functions of Babbage’s operation cards and variable cards. Each
instruction had the format:
A1 A2 OP
, where A1 and A2 are registers storing the operands
and OP is the operation to be performed( e.g. +,-,x,%). Mark I, was able to do a single
addition in 6 seconds and division in 12 seconds.
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