ok thanks for the reply. so as RX and tx pins operates at 13V
Typically +12v on Tx or Rx line indicates space or 0, while -12v indicates mark or 1.
Any voltage +3v to +15V is interpreted as a space, -3V to -15V is a mark. -3v to +3v is invalid.
This assumes original RS232 spec. The original spec is abused and modified in many modern devices.
CD (carrier detect) and RI (ring indicator) are rarely used any more, but were signals indicating modem and telephone line status.
DTR and DSR originally signalled the status of modem and terminal, but now tend to be just alternatives to RTS/CTS handshakes.
Now you may see why many modern applications just use ground, Tx and Rx. The uses of the other signals were complex enough when they were used for modem links. Now that the other signals are mis-used for many other uses, the meanings have become almost unfathomable.
If you really want to know the "standard" uses for the other signals, then a lot of googling will be needed. But you will probably find information on RS232 use, not the many deviations to the original standard.
Not sure how clear I have been, but a full explanation would fill many books and still be incomplete.
EDIT: A pic will output +5V (or maybe +3.3V) for a mark (1) and 0v for a space (0). The above is the other side of level converter (maybe MAX232 or MAX3232) where RS232 voltages exist. Never connect PIC directly to PC.