The Pica-B Computer

ID
TR-79-12
Authors
Harvey Abramson, Mark Fox, J. Peck, V. Manis and M. Gorlick
Publishing date
January 1979
Abstract

The Pica-B computer is a simple abstract machine designed to:

  • facilitate the portability of a simple single user operating environment written in BCPL.
  • serve the pedagogic goal of providing a basis for teaching concepts of hardware and system architecture, systems programming and programming language design in a unified setting, and
  • serve as a possible solution to the current and future software crisis caused by the advent of the micro-computer.

The Pica-B is based on Richards' Intcode machine but differs from it in the addition of an (interrupt) status register and a PDP-11 style memory map of I/O devices. The status register and hence interrupt and device handlers may be programmed in Pica-B code (an extention of Intcode) or in a version of BCPL with an added inline code facility, the so-called \underline{vile} command. An example is given of how interrupts and I/O are handled in Pica-B computer.