18-bit computers

The PDP-1 (Programmed Data Processor-1) is the first computer in Digital Equipment Corporation's PDP series and was first produced in 1959. It is known for being the most important computer in the creation of hacker culture at the Massachusetts Institute of Technology, Bolt, Beranek and Newman, and elsewhere. The PDP-1 is the original hardware for one of the first video games, Steve Russell's 1962 game Spacewar!.

thumb|300px|right|Modified PDP-7 under restoration in Oslo, Norway thumb|200x200px|PDP-7 at Living Computer Museum

mainframe computer by IBM

thumb|TX-0 computer circuitry used Philco surface-barrier transistors, which were encapsulated in plug-in vacuum tubes for testing and easy removal. thumb|Philco surface-barrier transistor advertisement for the first high-frequency transistors, which were used in the TX-0 transistorized computer

American corporation involved in mainly aerospace, electronics, automotive, and credit reporting, etc.

The PDP-9, the fourth of the five 18-bit minicomputers produced by Digital Equipment Corporation, was introduced in 1966. A total of 445 PDP-9 systems were produced, of which 40 were the compact, low-cost PDP-9/L units.

The PDP-4 was the successor to the Digital Equipment Corporation's PDP-1.