42 (Set Base Address)

42000000 XX000000

YYYYYYYY YYYYYYYY

E0000000 80008000

X = mem range

Y = code in that mem range

This is used to change the mem range of a code. Most text mods are in the 90 mem range so you would add 42000000 90000000 to the beginning of a code. 80 and 81 are in the same range so you dont need this for that.