History of computing hardware Early digital computer characteristics Early digital computer characteristics

| Name_ | First_operational | Numeral_system | Computing_mechanism | Programming | Turing_complete_ |
|---|---|---|---|---|---|
| Zuse Z3 (Germany) | May 1941 | Binary floating point | Electro-mechanical | Program-controlled by punched 35 mm film stock (but no conditional branch) | In theory (1998) |
| Atanasoff–Berry Computer (US) | 1942 | Binary | Electronic | Not programmable—single purpose | No |
| Colossus Mark 1 (UK) | February 1944 | Binary | Electronic | Program-controlled by patch cables and switches | No |
| Harvard Mark I – IBM ASCC (US) | May 1944 | Decimal | Electro-mechanical | Program-controlled by 24-channel punched paper tape (but no conditional branch) | Debatable |
| Colossus Mark 2 (UK) | June 1944 | Binary | Electronic | Program-controlled by patch cables and switches | In theory (2011) |