Concept
The Z1 was a motor-driven mechanical computer designed by Konrad Zuse from 1936 to 1937, which he built in his parents' home from 1936 to 1938. It was a binary electrically driven mechanical calculator with limited programmability, reading instructions from punched celluloid film. The “Z1” was the first freely programmable computer in the world that used Boolean logic and binary floating-point numbers, however, it was unreliable in operation. It was completed in 1938 and financed completely by private funds. This computer was destroyed in the bombardment of Berlin in December 1943, during World War II, together with all construction plans. The Z1 was the first in a series of computers that Zuse designed. Its original name was "V1" for Versuchsmodell 1 (meaning Experimental Model 1). After WW2, it was renamed "Z1" to differentiate it from the flying bombs designed by Robert Lusser. The Z2 and Z3 were follow-ups based on many of the same ideas as the Z1. The Z1 contained almost all the parts of a modern computer, i.e. control unit, memory, micro sequences, floating-point logic, and input-output devices. The Z1 was freely programmable via punched tape and a punched tape reader. There was a clear separation between the punched tape reader, the control unit for supervising the whole machine and the execution of the instructions, the arithmetic unit, and the input and output devices. The input tape unit read perforations in 35-millimeter film. The Z1 was a 22-bit floating-point value adder and subtractor, with some control logic to make it capable of more complex operations such as multiplication (by repeated additions) and division (by repeated subtractions). The Z1's instruction set had eight instructions and it took between one and twenty-one cycles per instruction. The Z1 had a 16-word floating point memory, where each word of memory could be read from – and written to – the control unit. The mechanical memory units were unique in their design and were patented by Konrad Zuse in 1936.
