The Free On-line Dictionary of Computing (30 December 2018):
A minicomputer sold by DEC in 1964. It had a
memory cycle time of 1.75 microseconds and add time of 4
microseconds. I/O included a keyboard, printer, paper-tape
and dual transport DECtape drives (type 555).
DEC provided an "advanced" Fortran IIcompiler, a Symbolic
Assembler, Editor, DDT Debugging System, Maintenance
routines and a library of arithmetic, utility and programming
aids developed on the program-compatible PDP-4.
[DEC sales brochure].
The PDP-7 was considered reliable enough (when properly
programmed) to be used for control of nuclear reactors and
Around 1970 Ken Thompson built the operating system that
became Unix on a scavenged PDP-7 so he could play a
descendant of the SPACEWAR game.