Int 10 Fn 5100 - Video - Ax Pc - Register External Character [J]
AX = 5100h
BH = character width in bits (10h)
BL = character height (10h)
DX = character code (DH = F0h-F3h, DL=40h-7Eh,80h-FCh)
ES:BP -> character bitmap
Return: AL = status (00h successful, 01h failed)
See Also: AX=5101h,INT 1F"SYSTEM DATA"