Quote Originally Posted by EmbranceII
I have made a custom set of units for this purpose.
Now i have some question:
1)What needed to make a compiler?
2)What needed to make a interpeter?
3)What the difference between compiler/interpeter?
4)How fast each of them is?
For all 4 I'd recommend a very good article called Let's Build A Compiler! that is listed in the Library section of PGD, right here.

Quote Originally Posted by EmbranceII
5)In what language FPC is developed in?(lol,that a simple one)

Some direction would be good.
Thanks for your time!
Free Pascal, as far as I know, is actually built by the FPC itself. Lazarus, I know is buit under it. At the very least I don't know what they originally used to make the first couple of builds, but I'm guessing it was not FPC.