Programmed Data Processor – 7

The PDP-7, developed by Digital Equipment Corporation in 1964, is a multipurpose 18-bit digital computer designed for engineering and scientific applications. Its standard configuration includes a processor, 4096-word core memory (expandable to 32,768 words), real-time control, and an input/output console typewriter. Key performance specifications include a 1.75-microsecond core memory cycle, 3.5-microsecond add time, and support for up to 256 input/output stations with program interrupt.

The system features a comprehensive programming suite, including a Symbolic Assembler, Relocating Linking Loader, Symbolic Debugging Program (DDT-7) for on-line debugging, a Symbolic Tape Editing Program, and a FORTRAN II Compiler. FORTRAN II facilitates problem-oriented programming using English words and mathematical statements, supported by extensive input/output, arithmetic, utility, and maintenance routines. The PDP-7's instruction set includes both memory-reference and augmented instructions, offering microprogramming capabilities.

The hardware architecture incorporates a bus-based input/output subsystem for flexible expansion. Optional equipment significantly extends its capabilities, including additional core memory, an Extended Arithmetic Element for enhanced arithmetic, drum systems for mass storage, an Automatic Priority Program Interrupt, and a wide array of peripherals such as CRT displays, plotters, light pens, paper tape and card equipment, line printers, data communication systems, magnetic tape units, and analog-to-digital converters. Digital Equipment Corporation also provided training, assistance, and maintained the DECUS (Digital Equipment Computer Users' Society) library to foster information and program exchange among users. The design prioritizes ease of programming, operation, and maintenance through features like marginal checking and diagnostic programs.