Modern Operating Systems by Herbert Bos ...
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Modern Operating Systems by Herbert Bos and Andrew...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf-M ODERN O PERATING S YSTEMS
Modern Operating Systems by Herbert...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf-M ODERN O PERATING S YSTEMS
Page 38
SEC. 1.2
run, we will look at successive generations of computers to see what their operat-
ing systems were like. This mapping of operating system generations to computer
generations is crude, but it does provide some structure where there would other-
wise be none.
The progression given below is largely chronological, but it has been a bumpy
ride. Each development did not wait until the previous one nicely finished before
getting started. There was a lot of overlap, not to mention many false starts and
dead ends.
Take this as a guide, not as the last word.
The first true digital computer was designed by the English mathematician
Charles Babbage (1792–1871).
Although Babbage spent most of his life and for-
tune trying to build his ‘‘analytical engine,’’ he never got it working properly be-
cause it was purely mechanical, and the technology of his day could not produce
the required wheels, gears, and cogs to the high precision that he needed. Needless
to say, the analytical engine did not have an operating system.
As an interesting historical aside, Babbage realized that he would need soft-
ware for his analytical engine, so he hired a young woman named Ada Lovelace,
who was the daughter of the famed British poet Lord Byron, as the world’s first
programmer. The programming language Ada
is named after her.
1.2.1 The First Generation (1945–55): Vacuum Tubes
After Babbage’s unsuccessful efforts, little progress was made in constructing
digital computers until the World War II period, which stimulated an explosion of
activity. Professor John Atanasoff and his graduate student Clifford Berry built
what is now regarded as the first functioning digital computer at Iowa State Univer-
It used 300 vacuum tubes.
At roughly the same time, Konrad Zuse in Berlin
built the Z3 computer out of electromechanical relays.
In 1944, the Colossus was
built and programmed by a group of scientists (including Alan Turing) at Bletchley
Park, England, the Mark I was built by Howard Aiken at Harvard, and the ENIAC
was built by William Mauchley and his graduate student J. Presper Eckert at the
University of Pennsylvania. Some were binary, some used vacuum tubes, some
were programmable, but all were very primitive and took seconds to perform even
the simplest calculation.
In these early days, a single group of people (usually engineers) designed,
built, programmed, operated, and maintained each machine. All programming was
done in absolute machine language, or even worse yet, by wiring up electrical cir-
cuits by connecting thousands of cables to plugboards to control the machine’s
basic functions. Programming languages were unknown (even assembly language
was unknown). Operating systems were unheard of. The usual mode of operation
was for the programmer to sign up for a block of time using the signup sheet on the
wall, then come down to the machine room, insert his or her plugboard into the
computer, and spend the next few hours hoping that none of the 20,000 or so vac-
uum tubes would burn out during the run. Virtually all the problems were simple

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