This is an interesting program for a couple reasons.  First though; this program is a detailed schematic and instructions on how to make an RS232 adapter for the Commodore 64 user port.  The cool thing about the schematic is that you can scroll through it and see how all the IC's are connected to the user port connector.  The other unrlated thing that's neat about this program is that the text for the description on how to build the adapter is in the file but you can't view it when loaded even though it's a BASIC program.  I wonder how the text was imbeded in the file.