Os8088: A powerful Mac-like OS for the IBM XT, 286, 386

Os8088 is a graphical operating system written entirely in assembly language that recreates a 1984 Macintosh-style interface for vintage IBM computers using Intel 8086/8088 processors, fitting entirely within 256KB of RAM. The system boots directly from a floppy disk without DOS, featuring overlapping windows, pull-down menus, a serial mouse, and notably, pre-emptive multitasking—something the original Macintosh lacked. The hobby project consists of 66,183 lines of hand-written real-mode assembly code and can run multiple applications simultaneously on processors from 1978.