DOS_OUTPUT_METHOD

This variable has meaning only on MS-DOS systems. It controls the method the runtime uses to display screen output.

Set this variable to "0" or "HARDWARE" to cause the MS-DOS runtime to display screen output by directly accessing the video hardware. This is the default unless the CODE_SYSTEM variable has a non-zero value.

Set this variable to "1" or "BIOS" to cause the MS-DOS runtime to perform screen output by calling the machine's BIOS. This is useful in cases where you want to "trap" the output with some program that can examine the calls to the BIOS.

If you set the CODE_SYSTEM variable to anything other than ASCII (value "0"), then the BIOS method is used automatically. This ensures that double-byte character sets are handled correctly.

You can also use this option to turn off the optimization of screen output. The extended MS-DOS runtime sends characters to the screen only if they differ (or their attributes differ) from characters that are already on the screen. To turn off this screen optimization, set DOS_OUTPUT_METHOD to "2" or "HARDWARE-NO-OPTIMIZE" for the HARDWARE method without optimization, or set it to "3" or "BIOS-NO-OPTIMIZE" for the BIOS method without optimization. The default method is "0" (HARDWARE with optimization).