Pic18F4XXX USB port

Does anyone knows how to work with USB port at pic18f4xxx (Pic18f4550 or Pic18f4455). And how to use USB at pc programs (C or VB)??

thanks ahead.

Check the application notes at MicroChip, they show both PIC and PC sides of USB interfaces - they even give full source code for their USB PICKit 1 programmer.

There are a lot of places you should check out, and I would highly recommend you do some google searches, and read as much as you can. I can tell you from personal experience that PIC USB interfacing is quite complicated and it's easy to get in over your head.

For starters, I have a basic tutorial on getting started with PIC USB interfacing using C# on the PC side, and the microchip C18 Compiler on the PIC side:
http://eegeek.net/content/view/13/32/

There's also a pretty popular wiki with lots of useful info:
**broken link removed**

And also, the microchip USB forum is a MUCH better place for you to ask questions, there are a lot more people on there with more experience with PIC USB interfacing:
**broken link removed**