I should first of all say sorry to you as this topic has been discussed a lot in this forum. Still I couldn't find a point as below:

Assume a remote control which is totally blank initially. Now it wants to learn the codes transmitted by other remotes. The other remote can be anyone in the world.
The learning remote will receive IR code from the other remote, store it in its memory, assign it to some specific key on it and use the code later for transmission. So it will duplicate the other remote.

Well, the flow seems pretty easy, but I have stuck on a point that I don't know at all the parameters of the other remote. i.e. the carrier frequency, no. of bits, etc. Now there are some keys on a remote (like the vol. up/down on TV remote) which when kept pressed, keep sending the code continuously. In this case, how to detect the end of code? For single press keys, like power off/on, it might be easy as I can detect the end of code, when the signal stops on the IR receiver. But for continuous signal, how to do it?

Any ideas?
p.s. I have to do it in C only. if any website or link is there, welcome.
thanks................