The ZERO was the first general purpose computer that Kosten and Van der Poel build at the PTT. It wasn't designed for actual use though, but merely as a test project to gain some experience and insight in building a relay computer. It was therefore an extremely simple machine and seen as a 'toy' computer. The name was also not an acronym but more a product number. It whad only two built in functions: addition and subtraction.

Functional bits

It was controlled with four so called 'functional bits' that controlled 6 relays to select the different operations. This was made to keep things simple, but when the ZEBRA was designed it became the inspiration of what made the ZEBRA such a special machine.


The device was developed between 1950 and 1952. When it was finished it was in use for roughly two months after which Kosten and Van der Poel moved on to build the PTERA. Unfortunately nothing of ZERO has been saved[1].


  • Built from 1950 to 1952
  • In operation for 2 months
  • Extremely simple design
  • Memory: 1 track of 32 words on a magnetic drum
  • 2 built-in functions: Addition and Subtraction
  • Controlled by a control box consisting of only 6 relays which where controlled by 4 'functional bits'
  • 'Programming' done by manipulating functional bits


  1. Kranakis, E. , "Early Computing in the Netherlands", CWI Quarterly, vol. 1, issue 4, pp. 61-84, 12/1988.