Today in 1983, Microsoft announced Windows, “a window manager and graphical-device interface,” saying it will ship the software to dealers “in April (although a product like Windows is difficult to predict and may take longer),” reported John Markoff in InfoWorld.
Martin Campbell-Kelly and William Aspray in Computer: A History of the Information Machine:
Microsoft Windows was the last of the new operating systems for the PC to appear. Microsoft began work on a graphical user interface project in September 1981, shortly after Gates had visited Steve Jobs at Apple and seen the prototype Macintosh computer under development. The Microsoft project was named Interface Manager but was later renamed Windows in a neat marketing move “to have our name basically define the generic.” It was estimated that it would take six programmer-years to develop the system. This proved to be a gross underestimate. When version 1 of windows was released in October 1985… it was estimated that the program contained 110,000 instructions and had taken eighty programmer-years to complete.