Hey ,
you can visit this site for C program demos and tutorials. Programming for PIC is the same as the C programming we have learned except we have to change the value of the variables and the input and output port names are to be used. Its simple and your second year knowlwdge of C is enough.

Different model PICs are available and they may differ in their memory capacity, clockspeed and the pin positions but most of them are 40 pin ICs. adder,amplifier and rectifier are simple circuits. RS232 is the serial port of the computer. It means that your computer must have a serial port. more: http://camiresearchData_Com_Basics/RS232_standard.html

Pic programming can be done in softwares like microC pro or L.E.T PicBasic Pro,PICALL. They are for compiling the C code. Testin means running the code in the PIC and verifying if it works. You can download PICsimulator . A/d and USART are ports on the computer.