INT 21 - DOS 1+ - SET INTERRUPT VECTOR
AH = 25h
AL = interrupt number
DS:DX -> new interrupt handler
Notes:  this function is preferred over direct modification of the interrupt
vector table
some DOS extenders place an API on this function, as it is not
directly meaningful in protected mode
SeeAlso: AH=35h

See also: 212501

2125 - DOS 1+ - SET INTERRUPT VECTOR