from the manual (it would be var_name.<entry from below>)
Code:
lowbyte
highbyte
byte0
byte1
lownib
highnib
nib0
nib1
nib2
nib3
i don't think it'd ever be nescasary to access a single byte in a word in the robot code since inputs and outputs are limited to bytes. maybe as a clever optimization or something, though.
Stephen