Which language are compilers written in?

Question

And how does it compile to machine code?

Answer 1

You can find few relevant comments here.
https://www.sololearn.com/Discuss/2730379/?ref=app
https://www.sololearn.com/discuss/2620995/?ref=app
https://www.sololearn.com/discuss/1356559/?ref=app

Answer 2

C is run by compiler which compiles whole code at a time

Which converts whole code of high level language to machine language