A Macintosh System 1-style desktop for the Intel 8086, written entirely in
real-mode assembly and booted from a floppy. Overlapping windows, pull-down menus, a serial
mouse, loadable programs — and pre-emptive multitasking, which the real 1984 Macintosh
never had.
os8088 boots from the first sector of a floppy into a graphical desktop. There is no DOS
underneath it and no command line anywhere in it — the 512-byte boot sector loads a
40KB kernel, the kernel works out which display adapter the machine has and switches it
into graphics, borrows the video card’s own 8×8 character set, and puts up a menu bar.
Everything after that is the interface you remember from a 1984 Macintosh: windows you
drag by the title bar with a rubber-band outline, menus you pull down and drag through,
a close box and a minimize box, icons for each floppy drive, and a dock along the bottom
with one tile per running program. Programs load from a second floppy and run as
first-class applications, several at a time.
The whole thing fits in 256K of RAM on an Intel 8086 or 8088 — the processor in the
original IBM PC and PC/XT. It is a hobby project, it is finished enough to use, and the
source is 66,183 lines of NASM you can read in an afternoon.
Every figure below comes from the build, not from memory.
Four of the things it is actually good at. There are more on thescreenshots page.
Everything above was captured in an emulator. In August 2026 someone wrote the disk
images onto actual floppies and booted them on three period machines — a 1981 IBM 5150,
a Toshiba T1100 Plus and a 286 — and photographed the results.
In February 1985 Digital Research shipped GEM 1.0 for the IBM PC: a Macintosh-style
desktop with overlapping windows and icons, running on stock XT hardware. Apple sued.
The settlement led to GEM Desktop 2.0 in 1986, which removed overlapping windows and
desktop icons on the PC — while the Atari ST version, not covered by the agreement,
kept them.
So the PC did briefly have this, and then it did not. os8088 is a rebuild of roughly
that idea, from scratch, forty years later, on the same class of machine — plus the
pre-emptive multitasking that neither GEM nor the Macintosh of the period offered.
The browser demo boots the real floppy image in an emulated PC — same bytes you would
write to a disk. If you would rather run it yourself, the download page has 360K images for
period hardware and 86Box, and 1.44MB images for QEMU.