Digital computers
Electromechanical
The US Navy had developed an electromechanical analog computer small enough to use aboard a submarine in 1938. This was the Torpedo Data Computer, which used trigonometry to solve the problem of firing a torpedo at a moving target. Similar devices were developed in other countries as well during World War II.
Early electromechanical was digital computer; electric switches
drove mechanical relays to perform the calculation. These devices had a
low operating speed and were eventually superseded by much faster
all-electric computers, using vacuum tubes. German engineer Konrad Zuse created The Z2 in 1939, was one of the earliest examples of an electromechanical relay computer.In 1941, Zuse followed his earlier machine up with the Z3, the world's first working electromechanical programmable, fully automatic digital computer. The Z3 was built with 2000 relays, implementing a 22 bit word length that operated at a clock frequency of about 5–10 Hz.Program code was supplied on punched film
while data could be stored in 64 words of memory or supplied from the
keyboard. It was quite similar to modern machines in some respects,
pioneering numerous advances such as floating point numbers. Rather than the harder-to-implement decimal system (used in Charles Babbage's earlier design), using a binary
system meant that Zuse's machines were easier to build and potentially
more reliable, given the technologies available at that time.The Z3 was Turing complete.
Vacuum tubes and digital electronic circuits
Tommy Flowers,The engineer, working at the Post Office Research Station in London in the 1930s, began to explore the possible use of electronics for the telephone exchange. Experimental equipment that he built in 1934 went into operation five years later, converting a portion of the telephone exchange network into an electronic data processing system, using thousands of vacuum tubes.In the US, John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed and tested the Atanasoff–Berry Computer (ABC) in 1942,the first "automatic electronic digital computer".This design was also all-electronic and used about 300 vacuum tubes,
with capacitors fixed in a mechanically rotating drum for memory.
Enigma |
was first attacked with the help of the electro-mechanical bombes. To crack the more sophisticated German Lorenz SZ 40/42 machine, used for high-level Army communications, Max Newman and his colleagues commissioned Flowers to build the Colossus.He spent eleven months from early February 1943 designing and building the first Colossus.After a functional test in December 1943, Colossus was shipped to Bletchley Park, where it was delivered on 18 January 1944 and attacked its first message on 5 February.
Colossus was the world's first electronic digital programmable computer.
It used a large number of valves (vacuum tubes). It had paper-tape
input and was capable of being configured to perform a variety of boolean logical operations on its data, but it was not Turing-complete.
Nine Mk II Colossi were built (The Mk I was converted to a Mk II making
ten machines in total). Colossus Mark I contained 1500 thermionic
valves (tubes), but Mark II with 2400 valves, was both 5 times faster
and simpler to operate than Mark 1, greatly speeding the decoding
process.
The U.S. built ENIAC
(Electronic Numerical Integrator and Computer) was the first electronic
programmable computer built in the US. Although the ENIAC was similar
to the Colossus it was much faster and more flexible. Like the Colossus,
a "program" on the ENIAC was defined by the states of its patch cables
and switches, a far cry from the stored program
electronic machines that came later. Once a program was written, it had
to be mechanically set into the machine with manual resetting of plugs
and switches.
It combined the high speed of electronics with the ability to be
programmed. It could add or subtract 5000
times a second, a thousand times faster than any other machine. It also
had modules to multiply, divide, and square root. High speed memory was
limited to 20 words (about 80 bytes). Built under the direction of John Mauchly and J. Presper Eckert
at the University of Pennsylvania, ENIAC's development and construction
lasted from 1943 to full operation at the end of 1945. The machine was
huge, weighing 30 tons, using 200 kilowatts of electric power and
contained over 18,000 vacuum tubes, 1,500 relays, and hundreds of
thousands of resistors, capacitors, and inductors.
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