While Apple is busy putting the iPad into Mac OS X, someone got busy putting DOS into the iPad: Apple-approved iDOS will get you a C:\> prompt. Why? Here are some reasons: PC Tetris. And Xenon 2. And Wing Commander. Updated
And X-Wing. And TIE Fighter. And Day of the Tentacle. And the Indy games.
Those were the times. The times of manual management of 64KB upper memory blocks and autobat/config.sys tuning. And Windows 3.0:
iDos is based on open source emulator DOSbox and includes some abandonware and freeware built-in. You can install your own programs too, and emulates keyboard, mouse support, and various video modes for $0.99.