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Konrad Zuse must be credited with the following fundamental inventions in the
area of computing development, where most of them were implemented in the machines
Z1 (1938), Z3 (1941) and Z4 (1945), with the exception of the Plankalkül:
- The use of the binary number system for numbers and the circuits.
- The use of floating point numbers, along with the algorithms for the translation
between binary and decimal and vice versa.
- An algorithm for the non-restoring calculation of the square-root. With this
algorithm, the square-root can be calculated with n steps, if n is the number
of digits. This fine method was not known in the US in 1949.
- The carry-look ahead circuit for the addition operation.
- Look-Ahead: The program is read two instructions in advance, and it is tested
whether memory instructions can be performed ahead of time.
- Pseudo-memory: In case the look-ahead mechanism finds that a number that is
to be restored is needed again within the next two instructions, the number
id placed in a register of mechanical contacts where it is available with no
access time. For this purpuse, the memory has two registers of reading contacts.
- Special values (Sonderwerte): If a result exceeds the capacity of the arithmetic
unit, it is designed as Sonderwert. This principle guarantees that the machine
always calculates correctly.
- The most unusual feature was undoubtedly the mechanical binary cells that made
up the memory. The memory has 64 words with 32 bits (Z1 and Z4). These devices
were completely different from mechanisms in contempory cash registers or desk-top
calculators. The elements could be used not only for storage, but also for calculation,
for example for address coding. A relay memory would have required about 2500
relays which would have more than doubled the size and the weight of the machine
Z4.
- The Plankalkül as the first complete high-level language of the world in 1945/46
(final edition).
All these ideas were Konrad Zuses personal achievements. In one or two cases
he was perhaps not the first inventor, but he certainly had no knowledge what
was done elsewhere; Until 1950 he lived in complete isolation from the world
outside Germany.
Slav Petrov
2001-07-02