They did make a few changes, such as in window hooks. Compare http://www.os2museum.com/files/docs/win10sdk/windows-1.03-sdk-prgref-1986.pdf http://www.os2museum

They did make a few changes, such as in window hooks. Compare http://www.os2museum.com/files/docs/win10sdk/windows-1.03-sdk-prgref-1986.pdf http://www.os2museum.com/files/docs/win10sdk/windows-1.03-sd... and http://www.os2museum.com/files/docs/win20sdk/windows-2.0-sdk-prgref-1987.pdf http://www.os2museum.com/files/docs/win20sdk/windows-2.0-sdk... for example. Actually, this makes me wonder if they never bothered with Windows 2.x and went directly to OS/2 Presentation Manager in 1987.