thanks for the link bill. one last question is that the socket for the programming ic is 16 pin(con3) rite. so will i not be able to program ics having more number of pins?
CON2 (ICD) is used to program PICs while they are on the target board. That saves a lot of time, and wear&tear on the PIC. It also allows you to program any size chip even surface mount!
To use it you place a 2x5 pin header on the target and connect it to CON2 using a ribbon cable.
To program other then 18 pin chips out of circuit I made a simple board with one socket for each size PIC. You could do like the programmers do and use a single combo socket setup but then you have to figure out where to put the chip. Easier this way, sockets are cheap. But I only use it when programing PICs for proven designs like the Junebug.