ISIS (operating system)

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ISIS (Intel System Implementation Supervisor) was an early operating system for Intel 8080/8085 microprocessors.

- History: Began in 1975, created by Ken Burgett and Jim Stein under Steve Hanna and Terry Opdendyk for the Intel Microprocessor Development System (MDS) with two 8-inch floppy drives. It later evolved into ISIS-II, used with the PL/M compiler, assembler, linker, and an In-Circuit Emulator (Steve Morse).
- Hardware: Built on an early MDS-800 prototype, the same era hardware Gary Kildall used for CP/M development.
- Interface: Terminal-like and somewhat CP/M-like. Files opened by name and returned a handle. Devices are named with colons (e.g., :F0:, :F1: for floppies; :LP: for printer). Each diskette has a single directory, with no subdirectories.
- ISIS-II features: Includes standard OS commands (COPY, DELETE, DIR, RENAME, FORMAT) and debugging tools (assembler, linker, debugger). Two editors are provided: AEDIT (with macros) and CREDIT. Editing is done directly on diskette, and a .BAK backup is created automatically.
- Requirements: Needs at least 32 KB RAM; 8080/8085 CPU with a 64 KB address space. In MDS-800/Series-II, the Monitor occupies F800h–FFFFh.
- Disks and formats: 8-inch disks, single-sided 250 KB FM or 500 KB MMFM. ISIS-PDS used 720 KB 5¼-inch disks. ISIS-IV ran on the iMDX-430 Series-IV Network Development System-II and was not fully compatible with other setups.
- Other tools: Intel ASM80, PLM-80, BASIC-80, COBOL-80, FORTRAN-80 (and ASM86, ASM48, ASM51).
- Status: ISIS-II is now obsolete.