I/O Ports on HP High-End Calculators

TypeSubtype
-33 CF
Wire
-78 CF
USB
-78 SF
RS-232 Serial
-33 SF
Infrared
-127 CF
IrDA
-127 SF
HP-IR

“HP-IR” is the infrared system used by the HP-48,
and is not available in most of the subsequent models.

Models that are missing one of these four ports
use the alternative, e.g. the HP 50g has no HP-IR,
so it always uses IrDA, regardless of the setting of flag -127.
The HP 49G has no USB or infrared, so it always uses
RS-232 Serial, regardless of any of these flag settings.