If you one day is running a command driven program from a DOS-prompt like DB2 or for example an editor. Then running this command will enlarge the visible area which isn't bad when having a 17" monitor or bigger.

MODE 80 50

Note this can also be done in Windows, but another way in there is just to use the mouse to enlarge the DOS-prompt like any other window.

Note in Windows one can change a DOS-window to full screen by pressing the key combination ALT+Enter.