Introduction           Introduction to communication functions
 COM_BREAK()            Closes all active windows
 COM_CLOSE()            Closes either COM1: or COM2:
 COM_COUNT()            Determine no.  of characters in buffer
 COM_CTS()              Check "Clear to Send" signal
 COM_DCD()              Check "Data Carrier Detect" signal
 COM_DSR()              Check "Data Set Ready" signal
 COM_DTR()              Check DTR signal status
 COM_EVENT()            Return condition of character/MSR/LSR
 COM_FLUSH()            Reject characters in data buffer
 COM_HARD()             Determine hardware handshake
 COM_INIT()             Set interface configuration
 COM_KEY()              Monitor interfaces
 COM_LSR()              Examine "Line Status Register"
 COM_MCR()              Read "Modem Control Register" status
 COM_MSR()              Check "Modem status Register"
 COM_OPEN()             Open COM1: or COM2:
 COM_READ()             Read characters in buffer
 COM_RING()             Check serial interface Ring status
 COM_RTS()              Check "Request to Send" signal
 COM_SEND()             Send characters to interface
 COM_SOFT()             Implement software handshake
 COM_SOFT_R()           Check receive flag
 COM_SOFT_S()           Check send flag