A PIC, assuming that you are talking about a AB 1747-PIC, is a Personal computer interface converter. It is used to connect a computer to a SCL 500 AB PLC. Some of the processors didn't have a rs232 port and it was used mostly for hooking up a laptop to the PLC for program downloading and trouble shooting. We still us them for trouble shooting with our laptop on PLC's not connected to a PC (stand alone PLC's).
Hope this helps.
Daymond
A generic PIC is a microprocessor containing many logic gates, analogue to digital converters etc. It can perform many tasks. Programming is required to get it to do what you want. If you are not familiar with the programming aspect, it will take you quite a while to achieve your end result.