Just installed this amazing game but I am not able to quit the game during the session.
I believe Ultima IV was made in the time before you could exit a program. After you saved, you simply turned off your computer.
The only way to quit Ultima IV is to either exit DosBox ([Alt]-[Enter]) and hit the X in the top right-hand corner, or execute it with 3rd party software like xu4 (http://xu4.sourceforge.net
/) or ScummVM (https://www.scummvm.org
/), and then use their hotkeys to exit.