compilers

how do compilers work ?
i mean when you have say c or c++ code or lisp program, how does it turn it into machine code ?
isnt it too complicated and take a lot of machine code ?
or like scheme tail loop, how is it done . its hard to convert just one loop
or like c++ classes theres no clases in machine assmebly
i dont understand

thanks

please answer my questions in first post