ISIS (operating system)

ISIS, short for Intel System Implementation Supervisor, is an operating system for early Intel microprocessors like the 8080. It was originally developed by Ken Burgett under the new management of Bill Davidow for the Intel Microprocessor Development System starting in 1975,[1][2][3] and later adopted as ISIS-II for systems with floppy drives.

Written inAssembler, PL/M
Working stateHistoric
Source modelClosed source
Marketing targetexclusively for Intel Microprocessor Development System
PlatformsIntel 8080, Intel 8085


Communication with the user is terminal-like. Its user interface is somewhat CP/M-like, even from the program interface point of view. For file opening, the program sends the name of file and gets back a handle. Each device has a name, which is entered between a pair of colons (:F0: and :F1: are floppies, :LP: is printer, etc.). Each diskette has one directory and no subdirectories. ISIS-II has been distributed as part of the Intel Microprocessor Development System and includes standard operating system commands (copy, delete, dir, rename, format)[3] and debugging software (assembler, linker and debugger for external debugging in developed device). There are two editors, one of which, AEDIT, contains editing macros support. File editing is provided directly on diskette (a .BAK file is always created). The other editor is CREDIT.

ISIS-II needed at least 32 kilobytes of RAM, the 8080/8085 CPU maximum address space was 64 kilobytes. In the MDS-800 and Series-II, the Monitor occupied F800h to FFFFh. Floppy disk format was 8-inch single-sided, 250 KB single-sided, single-density FM, or 500 KB single-sided, double-density MMFM. ISIS-PDS was also software and media incompatible and unique, it came on 720 KB DSDD 5¼-inch floppies with the Intel personal development system (iPDS-100).

The ISIS-IV operating system was another incompatible (even with other Intel development systems) that ran on the iMDX-430 Series-IV Network Development System-II.

Intel ASM80, PLM-80, BASIC-80, COBOL-80, FORTRAN-80 were all available for ISIS-II. ASM86, ASM48, ASM51 were available as well.


The following list of commands are supported by the ISIS-II console.[4]

See also


  1. Shustek, Len (2016-08-02). "In His Own Words: Gary Kildall". Remarkable People. Computer History Museum.
  2. Kildall, Gary Arlen (2016-08-02) [1993]. Kildall, Scott; Kildall, Kristin (eds.). "Computer Connections: People, Places, and Events in the Evolution of the Personal Computer Industry" (Manuscript, part 1). Kildall Family. Retrieved 2016-11-17. Cite journal requires |journal= (help)
  3. ISIS, Intellec, PL/M and Intel
  4. ISIS II Users Guide
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