How a $50,000 clone of CP/M rode the IBM PC deal into the most valuable monopoly in software history, fought the 640K barrier for a decade, papered DOS over with a graphical shell, unified consumers and engineers on Windows 95, ran two completely different operating systems in parallel for years, and finally collapsed them into a single NT kernel whose Win32 ABI Microsoft has refused to break for thirty years.
Win32
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The Story of MS-DOS and Windows