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An Architectural History of the Computer
It is not possible, nor particularly useful, to identify the date of the invention of the computer. Indeed it has always been the aspiration of humankind to create devices that simplify people's work. Thus is not surprising that people were envisioning mechanical devices to simplify the jobs of routine data processing and calculation even in ancient times. Instead, this discussion covers just a few of the major developments related to computer architecture.
In the context, one could consider the abacus already use as early as 500 B.C. by the ancient Greeks and Romans, to be an early predeccessor of the computer. Certainly, the abacus was capable of performing calculations and storing data. Actually if one were to build a binary numbered abacus, its calculation would resemble those of the computer very closely.
The abacus remained in common use until the 1500s and, in fact, is still considered and effective calculating tool in some cultures today. In the late 1500's, though, European inventors again began to put their minds to the problem of automatica calculation. Blaise Pascal a noted French mathematician of the 1600's invented a calculating machine in 1642 at the age of 19, although he never able to construct the machine.
In 1801, Joseph Marie Jacquard invented a loom that used to punched cards to control the patterns woven into cloth. The program provided by the punch of cards controlled rods that raised and lowered different threads in the correct sequence to print a particular pattern. This is the first documented application of the use of punched cards to hold a program for the use of a semiautomated, programmable machine.
Charles
Babbage, an English mathematician who lived nearly 1800 an English mathematician
who lived in the early 1800s, spent much of his own personal fortune attempting
to build a mechnical calculating machine that he called an "analytical
engine". The analytical engine resembles a computer in many conceptual
ways. Babbage's machine envisioned the use of Jacquard's punched cards
for input data and for the program, provided memory for internal storage,
performed calculations as specified by the program using a central processing
unit known as "mill", and printed output. Augusta Ada Byron,
Countess of Lovelace and the daughter of the poet Lord Byron, worked closely
with Babbage and developed many of the fundamental ideas of programming
and program design, including concepts of branches and loops.
A block diagram of the Babbage
analytical engine is shown in the figure.
The mill was capable of selecting one of the four arithmetic operations,
and of testing the sign of a number with a different program branch specified
for each result. The sequence of operation was specified by instructions
on the operations cards. The operation cards could be advanced or reversed
as a means of implementing a sort of "GOTO" instruction. The
second set of cards, known as variable cards, were used to specify particular
memory locations for data involved in the calculations. Babbage envisioned
a memory of 1000 50-digit decimal numbers. Each digit was to be stored
using a 10-toothed gear known as counter wheel. Although the analytical
engine was never completed, it should be apparent to you that it contains
all the essential elements of today's computers.
