Your choice of MS-DOS functions, ROM BIOS functions, or direct hardware access to solve a particular problem must always be balanced against performance needs; and, of course, the user is the final judge of a program's usefulness and reliability. Nevertheless, you can follow some basic guidelines, outlined below, to create well-behaved applications that are likely to run properly under future versions of MS-DOS and under multitasking program managers that run on top of MS-DOS, such as Microsoft Windows.