Communication Program For C64

EE JULY/AUGUST 1987 1 This program enables users of the popular Commodore C64 home computer to exchange messages between two ma- chines. No hardware whatsoever is needed to accomplish: • communication over several tens of metres using a three- wire connection-see Fig. I. Longer distances, or communi- cation over the telephone, of course require the use of a modem. • split screen operation: the upper half of the screen displays the operator"s input (LOCAL), the lower half displays the received messages (REMOTE). • full duplex communication, i.e. transmission and recep- tion are quasi-simultaneous pro- cesses. The flowcharts in Fig. 2 illus- trate the structure of the pro- posed program. TX is short for transmitter, RX for receiver. Note that screen pointer up- dating routines are not apparent from these diagrams. Unfortunately, since the C64 BASIC interpreter does not allow structured programming to be carried out, the constructs shown in the flowcharts are not readily dete...