os8088: Mac-style GUI OS for IBM PC XT in real-mode assembly
Original: Os8088: A powerful Mac-like OS for the IBM XT, 286, 386
Why This Matters
Demonstrates that modern multitasking GUI concepts can be implemented on 1980s 8086 hardware using minimal assembly code.
os8088 1.0 is a graphical OS for the IBM PC/XT built in real-mode x86 assembly, offering a Macintosh System 1-style desktop with overlapping windows, pull-down menus, and preemptive multitasking on hardware from the 1980s.
os8088 1.0 is a graphical operating system targeting the Intel 8086/8088 processor, designed to run on IBM PC/XT, 286, and 386 hardware. Written entirely in real-mode assembly and booted from a floppy disk, it delivers a desktop interface modeled after Macintosh System 1 — but notably adds preemptive multitasking, a feature the original 1984 Macintosh lacked. The OS supports VGA (640x480, 16 colors), Hercules monochrome (720x348), and CGA monochrome (640x200) display modes. Its kernel fits within 256KB of RAM and supports up to 12 simultaneous tasks with a preemption rate of 78,950 per second at 18.2Hz. Features include overlapping windows, pull-down menus, serial mouse input, and loadable programs from a software floppy. Built-in applications include a Note Pad (with per-instance 512-character buffers), Clock, Bounce animation, Control Panel, and Task Manager with a scrolling history graph. The scheduler can be toggled between preemptive and cooperative modes at runtime with no restart required. A live browser demo and floppy disk images are available for download, and source code is published on GitHub.