| Developer | Bell Labs |
|---|---|
| Written in | IBM's FORTRAN and North American's Symbolic Assembly Program (SAP) |
| Working state | Discontinued |
| Initial release | 1957 |
| Latest release | BE90 / 1968 |
| Platforms | IBM 704 |
| History of IBM mainframe operating systems |
|---|
BESYS (Bell Operating System) was an early computing environment originally implemented as a batch processing operating system in 1957 at Bell Labs for the IBM 704 computer.