The PDP-15 was the fifth and last of the 18-bit minicomputers produced by Digital Equipment Corporation. The PDP-1 was first delivered in December 1959:P.4 and the first PDP-15 was delivered in February 1970. More than 400 of these successors to the PDP-9 (and 9/L) were ordered within the first eight months.:p.16
The PDP-15 was the only 18-bit machine constructed from TTL integrated circuits rather than discrete transistors, and, like every DEC 18-bit system (except mandatory on the PDP-1, absent on the PDP-4) has an optional integrated vector graphics terminal, DEC's first improvement on its early-designed 34n where n equalled the PDP's number.
The first DEC-supplied mass-storage operating system available for the PDP-15 was DECsys, an interactive single-user system. This software was provided on a DECtape cartridge, of which copies were made for each user. This copied DECtape was then added to by the user, and thus was storage for personal programs and data. A second DECtape was used as a scratch tape by the assembler and the Fortran compiler.
One other operating system, developed on the PDP-7, was also available for the PDP-15:
- MUMPS, which was originally developed in 1966
- DIGITAL EQUIPMENT CORPORATION - Nineteen Fifty-Seven To The Present (PDF). Digital Equipment Corporation. 1975.
- "The Early Architectures of DEC".
- Bob Supnik. "Unearthing The PDP-15's Operating Systems" (PDF).
- Bob Supnik (19 June 2006). "Technical Notes on DECsys" (PDF).
- Bell, C. Gordon; Mudge, J. Craig; McNamara, John E. (May 12, 2014). Computer Engineering: A DEC View of Hardware Systems Design. Digital Press. p. 162.