When someone writes a new programming language, what do they write it IN?

Question

Please excuse my ignorance. I\'m dabbling in PHP and getting my feet wet browsing SO, and feel compelled to ask a question that I\'ve been wondering about for years:

Answer 1

I too had this question few months back. And I read few articles and watched some videos which helped me to start writing my own language called soft. Its not complete yet but I learned a lot of stuff from this journey.

Basic things you should know is how compiler works when it has to execute a code snippet. Compiler has a lot of phases like lexical analysis, semantic analyzer, AST(Abstract Syntax Tree) etc.

What I did in my new language can be found here - http://www.singhajit.com/writing-a-new-programming-language/

If you are writing a language for first time then all the best and you have a long way to go.