A transistorised version of the IBM 709 which was a very popular high end computer in the early 1960s. The 7090 had 32Kbytes of 36-bit core memory and a hardware floating point unit. Fortran was its most popular language, but it supported many others. It was later upgraded to the IBM 7094, and a scaled down version, the IBM 7040 was also introduced.
IBM 7090s controlled the Mercury and Gemini space flights, the Balistic Missile Early Warning System (until well into the 1980s), and the CTSS time sharing system at MIT.
The 7090 was not good at unit record I/O, so in small configurations an IBM 1401 was used for SPOOL I/O and in large configurations (such as a 7090/94) a 7040/44 would be directly coupled and dedicated to handling printers and card readers. (See the film Dr Strangelove).