The partnership soured quickly. Microsoft, seeing the rising tide of Windows 3.0, diverted its resources, leaving IBM to develop OS/2 2.0 from a messy codebase. By 1992, the divorce was final: Microsoft went all-in on Windows NT, while IBM carried OS/2 forward alone.
"If Microsoft ships Windows 3.0 with VxD support before we ship OS/2 1.3, we are dead. -- Dave, 10/12/1989"
, reflecting a "move fast" mentality in the late 80s that wouldn't pass modern automated code review standards Modern Accessibility os 2 source code
OS/2 did it in 1987 on a 6MHz 286 with 1MB of RAM. Windows didn’t get true preemptive multitasking until Windows 95 (and even that was flaky). Reading the OS/2 scheduler teaches you the eternal trade-off: fairness vs. responsiveness. Their solution (a time-slicing priority system with "critical section" boosts) is still used by QNX and VxWorks today.
If you are a developer today, you cannot legally download and compile the complete OS/2 kernel. But you can run ArcaOS. You can explore the leaked files as a historical curiosity (at your own legal risk). And you can marvel that, somewhere in a bank vault in Ohio, an ATM is still booting from a hard drive that reads an HPFS partition crafted by code written in 1991. The partnership soured quickly
, which attempts to rewrite the OS/2 subsystems as open-source. Tooling Documentation
The code reflects a transition from 16-bit to 32-bit architecture, which created unique complexities: Thunking Layers "If Microsoft ships Windows 3
Dave was right.
The most fascinating parts of the leak aren’t the algorithms—it’s the comments. Buried deep in the source files, you find developer rants, debugging notes, and strategic observations that were never meant for public consumption.