I believe the first C compiler was written in assembly language. Subsequent compilers have been written primarily in C and later, C++. However, that has nothing to do with learning C. You're really better off focusing on learning the basics of the language and saving history for later.
C are written probably using bison(syntax) and lex(lexical) analisators. if you want to get more information about "how to write your own programming language" you have to read book "Red dragon". And if you also have anything questions, try to ask me because in university I'm writing own scripting language such as python. I have some simple sources, but not complete project yet.