i am finished with the designing of the hardware. i need help for software part. i need the source files for these devices so that i can modify according to my needs.This is the first time i will be programming a PIC microcontroller. any kind of help in this regard is welcome.

 

I am sure if you designed the hardware, you would have had access to the datasheets for these devices.... that should have had all the info you needed. And Why don't you search Microchip's website for source code and applications notes for the devices you are using, I am sure if you did design the hardware, you should have already known about this.

 

i have searched microchip website unsuccessfully.i got the basic idea from tuxgraphics.org but that circuit used atmega and i have been instructed to use only PIC18F 4520 from my college.

 

Here:
http://www.microchip.com/wwwproducts/devices.aspx?ddocname=en010297
Look at the Tips and Tricks guide near the bottom. It's 5.82MB.

 

the help in tips and tricks is in assembly language. I need help in c language.
I will be thankful if you help me out.