| Year | Versions | Comment
| --- | --- | ---
| 1967 | 1? | PDP-6
| 1968 | 350-444
| 1969 | 530 | KA10 support?
| 1970 | | Virtual memory
| 1971 | 672-703 | Arpanet support
| 1972 | 720-724
| 1973 | 785-850
| 1974 | 915 | KL10 support
| 1975 | 994-998
| 1976 | 1025-1044
| 1977 | 1066-1097
| 1978 | 1099-1136 | PDP-6 support dropped
| 1979 | 1138-1168
| 1980 | 1173-1196
| 1981 | 1198-1256
| 1982 | 1256-1283
| 1983 | 1312-1360
| 1984 | 1361-1486
| 1985 | 1487-1539 | KS10 support
| 1986 | 1554-1588
| 1987 | 1591-1616
| 1988 | 1618-1632
| 1989 | 1633-1634
| 1990 | 1640-1644 | Last MIT version
| 1992 | 1645 | By Ken Harrenstien
| 1997 | 1647
| 2002 | 1648 | By Paul Svensson
| 2005 | 1649 | By Björn Victor
| 2007 | 1650