The Z1 was a mechanical computer designed by Konrad Zuse from 1935 to 1936 and built by him from 1936 to 1938. It was a binary electrically driven mechanical calculator with limited programmability, reading instructions from punched tape.The Z1 was the first freely programmable computer in the world which used Boolean logic and binary floating point numbers, however it was unreliable in operation. It was completed in 1938 and financed completely from private funds.