The Free On-line Dictionary of Computing (30 December 2018):
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
IBM 7090s controlled the Mercury and Gemini space flights, the
Balistic Missile Early Warning System (until well into the
1980s), and the CTSStime 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).