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KF5JRV > TECH 17.07.16 13:42l 151 Lines 7361 Bytes #999 (0) @ WW
BID : 6196_KF5JRV
Read: GUEST
Subj: Z3 Computer
Path: IW8PGT<CX2SA<ZL2BAU<N0KFQ<KF5JRV
Sent: 160717/1239Z 6196@KF5JRV.#NWAR.AR.USA.NA BPQK1.4.65
The Z3 was an electromechanical computer designed by Konrad Zuse. It
was the world's first working programmable, fully automatic digital
computer. The Z3 was built with 2,000 relays, implementing a
22-bit word length that operated at a clock frequency of about
5 - 10 Hz. Program code and constant data were stored on punched
film.
The Z3 was completed in Berlin in 1941. The German Aircraft
Research Institute used it to perform statistical analyses of
wing flutter. Zuse asked the German government for funding
to replace the relays with fully electronic switches, but
funding was denied during World War II since such development
was deemed "not war-important". The original Z3 was
destroyed in 1943 during an Allied bombardment of Berlin.
The Z3 was originally called V3 (Versuchsmodell 3, i.e.
Experimental Model 3) but was renamed to not be confused
with Germany's V-weapons. A fully functioning replica
was built in the 1960s by Zuse's company, Zuse KG, and
is on permanent display in the Deutsches Museum. The Z3
was demonstrated in 1998 to be, in principle,
Turing-complete.
Thanks to this machine and its predecessors, Konrad Zuse is
often regarded as the inventor of the computer.
Design and development
Zuse designed the Z1 in 1935 to 1936 and built it from 1936
to 1938. The Z1 was wholly mechanical and only worked for a
few minutes at a time at most. Helmut Schreyer advised Zuse
to use a different technology. As a doctoral student at the
Berlin Institute of Technology in 1937 he worked on the
implementation of Boolean operations and (in today's terminology)
flip-flops on the basis of vacuum tubes. In 1938 Schreyer
demonstrated a circuit on this basis to a small audience, and
explained his vision of an electronic computing machine - but
since the largest operational electronic devices contained
far fewer tubes this was considered practically infeasible.
Zuse decided to implement the next design based on relays.
The realization of the Z2 was helped financially by Dr. Kurt
Pannke, who manufactured small calculating machines. The Z2
was completed in 1939 and presented to an audience of the
Deutsche Versuchsanstalt fcr Luftfahrt ("German Laboratory
for Aviation") in 1940 in Berlin-Adlershof. Zuse was
lucky - this presentation was one of the few instances where
the Z2 actually worked and could convince the DVL to partly
finance the next design.
Improving on the basic Z2 machine, he built the Z3 in 1941,
which was a highly secret project of the German government.
Dr. Joseph Jennissen (1905 - 1977), member of the
"Research-Leadership" (Forschungsf fchrung) in the Reich Air
Ministry[16] acted as a government supervisor for orders of
the ministry to Zuse's company ZUSE Apparatebau. A
further intermediary between Zuse and the Reich Air Ministry
was the aerodynamicist Herbert A. Wagner.
The Z3 was completed in 1941 and was faster and far more
reliable than the Z1 and Z2. The Z3 floating-point arithmetic
was improved over that of the Z1 in that it implemented
exception handling. The exceptional values plus infinity,
minus infinity and undefined could be generated and passed
through operations. The Z3 stored its program on an external
tape, thus no rewiring was necessary to change programs.
On 12 May 1941 the Z3 was presented to an audience of scientists
including the professors Alfred Teichmann and Curt Schmieden
of the Deutsche Versuchsanstalt fcr Luftfahrt ("German Laboratory
for Aviation") in Berlin, today known as the German Aerospace
Center in Cologne.
Zuse moved on to the Z4 design; this was built days before the
war ended. The Z3 as a universal Turing machine
It was possible to construct loops on the Z3, but there was no
conditional branch instruction. Nevertheless, the Z3 was
Turing-complete - how to implement a universal Turing machine
on the Z3 was shown in 1998 by Rafal Rojas. He proposes
that the tape program would have to be long enough to execute
every possible path through both sides of every branch. It
would compute all possible answers, but the unneeded results
would be canceled out (a kind of speculative execution).
Rojas concludes, "We can therefore say that, from an abstract
theoretical perspective, the computing model of the Z3 is
equivalent to the computing model of today's computers. From
a practical perspective, and in the way the Z3 was really
programmed, it was not equivalent to modern computers."
From a pragmatic point of view, however, the Z3 provided a
quite practical instruction set for the typical engineering
applications of the 1940s - Zuse was a civil engineer who
only started to build his computers to facilitate his work
in his main profession.
The success of Zuse's Z3 is often attributed to its use of
the simple binary system. This was invented roughly three
centuries earlier by Gottfried Leibniz; Boole later used it
to develop his Boolean algebra. In 1937, Claude Shannon
introduced the idea of mapping Boolean algebra onto electronic
relays in a seminal work on digital circuit design. Zuse
however did not know Shannon's work and developed the
groundwork independently for his first computer Z1
which he designed and built from 1935 to 1938.
Zuse's coworker Helmut Schreyer built an electronic digital
experimental model of a computer using 100 vacuum tubes
in 1942, but it was lost at the end of the war.
The Tommy Flowers-built Colossus (1943) and the
Atanasoff - Berry Computer (1942) used thermionic valves
(vacuum tubes) and binary representation of numbers.
Programming was by means of re-plugging patch panels and
setting switches.
The ENIAC computer, completed after the war, used vacuum
tubes to implement switches and used decimal representation
for numbers. Until 1948 programming was, as with Colossus,
by patch leads and switches.
The Manchester Baby of 1948 and the EDSAC of 1949 were the
world's first computers that stored program instructions
and data in the same space. In this they implemented the
stored-program concept which is frequently (but erroneously)
attributed to a 1945 paper by John von Neumann and colleagues.
Von Neumann is said to have given due credit to Alan Turing,
and the concept had actually been mentioned earlier by Konrad
Zuse himself, in a 1936 patent application (that was rejected).
Konrad Zuse himself remembered in his memoirs: "During the war
it would have barely been possible to build efficient stored
program devices anyway." and Friedrich L. Bauer wrote:
"His visionary ideas (live programs) which were only to be
published years afterwards aimed at the right practical
direction but were never implemented by him."
Average calculation speed: addition - 0.8 seconds,
multiplication - 3 seconds
Arithmetic unit: Binary floating point, 22 bit, add,
subtract, multiply, divide, square root
Data memory: 64 words with a length of 22 bits
Program memory: Punched celluloid tape
Input: Decimal floating point numbers
Output: Decimal floating point numbers
Input and Output was facilitated by a terminal, with
a special keyboard for input and a row of lamps to
show results
Elements: Around 2,000 relays (1,400 for the memory)
Frequency: 5.3 Hertz
Power consumption: Around 4,000 watts
Weight: Around 1 tonne (2,200 lb)
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