(Multi-User System for Interactive Computing / System Product; originally "McGill University System for Interactive Computing") was developed at McGill University
in the late 1960s from an IBM
system called RAX (Remote Access). The system ran on IBM S/360
, and 4300-series mainframe
hardware, and offered novel features (for the time) such as file access control and data compression
. It was designed to allow academics and students to create and run their programs interactively on terminals
, in an era when most mainframe computing was still being done from punch cards
. Over the years, development continued and the system evolved to embrace e-mail
, the internet and eventually the WWW
. At its peak in the late 1980s, there were over 250 universities
and high school districts
that used the system in North
and South America
Early (circa 1977) versions of the system limited file names to six characters, and while files could be marked as private to a specific user, all users still shared a common library, and could not duplicate each other's filenames. One of the first major revisions to the file system included improvements to allow longer filenames, and provide each user with an individual library for private files.
One major advantage the system had in educational environments was that through the use of special lines called "control cards" at the top of a file, source files for any supported language could be automatically directed to the appropriate compiler (Fortran being the default), compiled, linked, and executed, (with compilation, linkage, and execution options also specified in control cards) simply by entering the filename on a command line.
The system supported a number of programming languages, including Fortran (both the IBM G-1 compiler and WATFIV), COBOL, APL, and VS-BASIC; it also provided a number of utilities, including several text editors, and a primitive text formatter called MUSIC/SCRIPT, which could be used in combination with a text editor for word processing.
A wide variety of terminals were supported as of 1980, including both EBCDIC-based units using IBM-proprietary protocols, and asynchronous ASCII-based units. Since terminals were connected through various types of front-end processors (as per common IBM timesharing practice both then and now), and could therefore function without CPU attention for a considerable amount of time, MUSIC used variable-length timeslices, which could, on compute-bound processing, reach a maximum of several seconds per timeslice.
The Sim390 emulator
that runs on Microsoft Windows
contains a demonstration system of MUSIC/SP. It is freely available. The demonstration system will also run under Hercules
, for those users who do not run Windows.