Microsoft released Windows 1.01 40 years ago, marking its first entry into graphical user interfaces with a WIMP-driven shell. Launched in 1985, it operated on DOS and required an Intel 8088 processor, 256KB of RAM, twin-floppy drives, and CGA graphics. A mouse was recommended but not necessary for navigation. At its release, Apple's Macintosh and home computers like the Atari ST and Commodore Amiga had already established graphical operating systems. Windows 1.01 included applications like Notepad, Paint, Clock, Calculator, and a game called Reversi. The interface featured tiled windows rather than overlapping ones. U.S. customers could purchase Windows 1.01 at launch for approximately 0, and version 1.02 was released in Europe in May 1986.