architecture - Compiler - front end back end

Question

I understand the structure of a compiler in regards to front-end and back-end. However, I am not sure why compilers are often divided into front-end and back-end. I am sure there are many reasons can you give me a few? because, most books / websites tell you what they are but fail to tell you why!

Thank you.

question from:https://stackoverflow.com/questions/9765414/compiler-front-end-back-end

Answer 1

The front-end deals with the language itself: scanning, parsing, the parse-tree. The back end deals with the target system: object code formats, the machine code itself, ... The two things don't have all that much to do with each other, and for a portable compiler it is highly desirable to use the same front-end with multiple backends, one per target.

You can take that further, as gcc does, and have a front/backend interface that is language-independent, so you can use different language front-ends with the same backend. In the old days this was called the MxN problem: you don't want to have to write MxN compilers where you have M languages and N target systems. The idea is to only have to write M+N compilers.