The book came out in 1990, the same year Windows 3.0 was released. Windows 1.0 was released in 1985 and 2.0 was released in 1987.
Almost noone used Windows until Windows 3.1. Not even engineering colleges. For intents and purposes, Windows does not really exist til 3.1 for most people. And that didn't even have a TCP/IP stack native; you had to install WinSock.