catflap.org Online Dictionary Query

  Multipop-68
       
           An early time-sharing operating system
          developed in Edinburgh by Robin Popplestone and others.  It
          was inspired by MIT' Project MAC, via a "MiniMac" project
          which was aborted when it became obvious that Elliot
          Brothers Ltd. could not supply the necessary disk storage.
          Multipop was highly efficient in its use of machine resources
          to support symbolic programming, and effective - e.g. in
          supporting the development of the Boyer-Moore theorem prover
          and of Burstall and Darlington's transformation work.
       
          It was not good at supporting the user programs which were
          then the standard fare of computing, e.g. matrix inversion.
          This arose from the fact that while the POP-2 compiler
          generated good code for function call (which is a lot of what
          layered systems like operating systems do) it did not generate
          efficient code for arithmetic or store access, because there
          was no way to police the generation of illegal objects
          statically.  ({Hindley-Milner type checking did not exist).
          Indeed, since many OS features like file-access were performed
          by function-call (of a closure) rather than an OS call
          requiring a context switch, POP-2 actually gained
          performance.
       
          Multipop68 was efficient primarily because the one language,
          POP-2 served all purposes: it was the command language for the
          operating system as well as being the only available
          programming language.  Thus there was no need to swap in
          compilers etc.  All store management was accomplished
          uniformly by the garbage collector, as opposed to having
          store management for the OS and store management for each
          application.
       
          There was a substantial amount of assembly language in
          Multipop68.  This was primarily for interrupt handling, and it
          is difficult to handle this without a real-time
          garbage-collector.
       
          [Edited from a posting by Robin Popplestone].
       
          (1995-03-15)