Michigan Terminal System - Features

Features

Some of the notable features of MTS include:

  • The use of Virtual memory and Dynamic Address Translation (DAT) on the IBM S/360-67 in 1967.
  • The use of multiprocessing on an IBM S/360-67 with two CPUs in 1968.
  • Programs with access to (for the time) very large virtual address spaces.
  • A straight forward command language that is the same for both terminal and batch jobs.
  • A strong device independent input/output model that allows the same commands and programs to access terminals, disk files, printers, magnetic and paper tapes, card readers and punches, floppy disks, network hosts, and an audio response unit (ARU).
  • A file system with support for "line files" where the line numbers and length of individual lines are stored as metadata separate from the data contents of the line and the ability to read, insert, replace, and delete individual lines anywhere in the file without the need to read or write the entire file.
  • A file editor ($EDIT) with both command line and "visual" interfaces and pattern matching based on SNOBOL4 patterns.
  • The ability to share files in controlled ways (read, write-change, write-expand, destroy, permit).
  • The ability to permit files, not just to other user IDs and projects (aka groups), but to specific commands or programs and combinations of user IDs, projects, commands and programs.
  • The ability for multiple users to manage simultaneous access to files with the ability to implicitly and explicitly lock and unlock files and to detect deadlocks.
  • Network host to host access from commands and programs as well as access to or from remote network printers, card readers and punches.
  • An e-mail system ($MESSAGE) that supports local and network mail with the ability to send to groups, to recall messages that haven't already been read, to add recipients to messages after they have been sent, and to display a history of messages in an e-mail chain without the need to include the text from older messages in each new message.
  • The ability to access tapes remotely, and to handle data sets that extend across multiple tapes efficiently.
  • The availability of a rich collection of well-documented subroutine libraries.
  • The ability for multiple users to quickly load and use a collection of common reentrant subroutines, which are available in shared virtual memory.
  • The availability of compilers, assemblers, and a Symbolic Debugging System (SDS) that allow users to debug programs written in high-level languages such as FORTRAN, Pascal, PL/I, ... as well as in assembly language.
  • A strong protection model that uses the virtual memory hardware and the S/360 and S/370 hardware's supervisor and problem states and via software divides problem state execution into system (privileged or unprotected) and user (protected or unprivileged) modes. Relatively little code runs in supervisor state. For example Device Support Routines (DSRs, aka device drivers) are not part of the supervisor and run in system mode in problem state rather than in supervisor state.
  • A simulated Branch on Program Interrupt (BPI) instruction.

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