os8088 1.0 delivers a Macintosh System 1-style graphical desktop for the Intel 8088 at 4.77MHz, written entirely in real-mode assembly and booted from a floppy. It provides overlapping windows, pull-down menus, a serial mouse, loadable programs, and pre-emptive multitasking — which the 1984 Macintosh lacked — all within 256K of RAM.

The 52,718-byte kernel includes scheduler, window manager, VGA/Hercules/CGA drivers, mouse driver, sound layer, file manager, loader, Task Manager, and Control Panel. The 512-byte boot sector probes the display adapter, switches to graphics, and borrows the video card's 8x8 character set. Twelve task slots with 1,536-byte stacks context-switch at 18.2Hz via the PC's timer interrupt.

Programs load from a second floppy into separate segments; Minesweeper is 1,510 bytes. The Task Manager shows live CPU and RAM meters. The source is 66,183 lines of hand-written NASM with no C, linker, or runtime. In August 2026 it was tested on a 1981 IBM 5150, Toshiba T1100 Plus, and a 286, running six programs simultaneously on a Hercules card.

It is not DOS, has no memory protection, no networking, and no hard-disk support — a complete hobby project that owns the machine from the boot sector up.