Defining characteristics of some early digital computers of the 1940s (In the history of computing hardware)
| Name | First operational | Numeral system | Computing mechanism | Programming | Turing complete |
| Zuse Z3 (Germany) | May-41 | 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) | Feb-44 | Binary | Electronic | Program-controlled by patch cables and switches | No |
| Harvard Mark I – IBM ASCC (US) | May-44 | Decimal | Electro-mechanical | Program-controlled by 24-channel punched paper tape (but no conditional branch) | Debatable |
| Colossus Mark 2 (UK) | Jun-44 | Binary | Electronic | Program-controlled by patch cables and switches | In theory (2011) |
| Zuse Z4 (Germany) | Mar-45 | Binary floating point | Electro-mechanical | Program-controlled by punched 35 mm film stock | Yes |
| ENIAC (US) | Jul-46 | Decimal | Electronic | Program-controlled by patch cables and switches | Yes |
| ARC2 (UK) | May-48 | Binary | Electronic | Stored-program in rotating drum memory | Yes |
| Manchester Small-Scale Experimental Machine (Baby) (UK) | Jun-48 | Binary | Electronic | Stored-program in Williams cathode ray tube memory | Yes |
| Modified ENIAC (US) | Sep-48 | Decimal | Electronic | Read-only stored programming mechanism using the Function Tables as program ROM | Yes |
| Manchester Mark 1 (UK) | Apr-49 | Binary | Electronic | Stored-program in Williams cathode ray tube memory and magnetic drum memory | Yes |
| EDSAC (UK) | May-49 | Binary | Electronic | Stored-program in mercury delay line memory | Yes |
| CSIRAC (Australia) | Nov-49 | Binary | Electronic | Stored-program in mercury delay line memory | Yes |
