PID controller and serin/serin2...help

i still new to programming PIC and PICBASIC PRO compiller. :(


how to write a PID controller ?...

my project is about controlling a DC motor using PID methode and can be remotely communicate with computer (hyperterminal).
i'm now using a 16F84A and communicate with serial port from PIC to PC.

how to make the PIC recieve more that 1 letter or number from PC?.
i still have the problem with the serin and serin2 command.

please can your all show me some sample, so i can learn and more understand.:)

i hope your all help.
:)