Z22

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See Z22 (handheld) for the Palm handheld

Z22, built 1956; now at ZKM in Karlsruhe.

The Z22 was the seventh computer model Konrad Zuse developed (the first six being the Z1, Z2, Z3, Z4, Z5 and Z11, respectively). One of the early commercial computers, the Z22's design was finished about 1955. The first machines built were shipped to Berlin and Aachen.

It has been said that the Z22 was the first computer with magnetic storage. As core memory and drum memory were invented earlier and were—by hearsay—used in military computer prototypes before, this is not assured knowledge, though. (The Whirlwind reportedly used magnetic core in 1953, and magnetic drum memory was commonly used a few years before that.)

The University of Applied Sciences, Karlsruhe still has an operational Z22 which is on permanent loan at the ZKM in Karlsruhe.

[edit] Technical data

The typical setup of a Z22 was:

14 words of 38-bit RAM implemented as core memory
38kByte magnetic drum storage
punch-card memory as bulk memory (input/output)
380V 16A three phase power supply
600 tubes working as flip-flops
electrical cooling unit, needing a water tap connection (water cooling, so to say)

The Z22 operated at 3kHz operating frequency, which was synchronous with the speed of the drum storage. The input of data was not only possible via punch-card reader, but also by directly programming drum storage or core memory using pushbuttons. The Z22 also had glow-lamps which showed the memory- and machine state as output.

[edit] Programming

The Z22 was designed to be easier to program than previous first generation computers. It was programmed in machine code with 38 bit instruction words, consisting of 5 fields:

the first 2 bits must always be 10
the next 5 bits contain a condition symbol
the next 13 bits contain an operation symbol
the next 5 bits contain a core memory address
the next 13 bits contain a drum memory address

There also was an assembly-like programming language called "Freiburger Code". It was designed to make programming programs for solving mathematical problems easier than writing machine code, and reportedly did so.