GPIB is abbreviation of General Purpose Interface Bus. 
GPIB is used, in order to connect a computer with a measurement machine 
(for example, oscilloscopes of Tektronix Inc.) by the cable with Dsub 
screw connector of 24pin and to control the measurement machine by the 
computer. 
Web Page of National Instruments Corporation which is a GPIB board maker 
for PC or Mac thinks that Page ( http://www.natinst.com/ ) is referred. 
Moreover, GPIB has also been the standard of IEEE-488. 
So, GPIB related information will be found, if you search technical 
books and Web Pages with a keyword "GPIB" and "IEEE-488". 
As for GPIB board, it is ordinary to be used by calling a function to 
the board from programming languages, such as BASIC and C, using 
attached driver software. 
Since the board is a GPIB card for AppleII, it is considered that a 
driver routine fundamental to on-board ROM is contained. 
The usage may be known when disassembling the ROM. 
Since the IC tip is a major for GPIB, pin connection of the data sheet 
of the IC and its on a printed circuit board shows the mode of 
operation, procedure required for initialization, and so on.