INT 21 - DOS 2+ - "SWITCHAR" - SET SWITCH CHARACTER
AX = 3701h
DL = new switch character
Return: AL = status
00h successful
FFh unsupported subfunction
Notes:  documented in some OEM versions of some releases of DOS
supported by OS/2 compatibility box
ignored by DOS 5.0

See also: 213700

213701 - DOS 2+ - "SWITCHAR" - SET SWITCH CHARACTER