alt Hacker Newscompiler creates a binary in elf format or other format which can be run given a shared object exists.
Intepreter either writes it in bytecode and then executes the bytecode line by line ?
Atleast that is what I believe the difference is , care to elaborate , is there some hidden joke of compiler vs intepreter that I don't know about ?
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I would generalize it to a compiler produces some sort of artifact that is intended to later be used directly, while for an interpreter the whole mechanism(source to execution) is intended to be used directly.
The same tool can often be used to do both. trival example: a web browser. save your web page as a pdf? compiler. otherwise interpreter. but what if the code it is executing is not artisanal handcrafted js but the result of a typescript compiler?
An interpreter runs the code as it is being read in.
A compiler processes the code and provides an intermediate result which is then "interpreted" by the machine.
So to take the "writes it in byte code" -- that is a compiler. "executes the byte code" -- is the interpreter.
If byte code is "machine code" or not, is really secondary.
I assume GP meant that a lot of compilers also interpret and interpreters also compile.
For compilers, constant folding is a pretty obvious optimization. Instead of compiling constant expressions, like 1+2, to code that evaluates those expressions, the compiler can already evaluate it itself and just produce the final result, in this case 3.
Then, some language features require compilers to perform some interpretation, either explicitly like C++'s constexpr, or implicitly, like type checking.
Likewise, interpreters can do some compilation. You already mentioned bytecode. Producing the bytecode is a form of compilation. Incidentally, you can skip the bytecode and interpret a program by, for example, walking its abstract syntax tree.
Also, compilers don't necessarily create binaries that are immediately runnable. Java's compiler, for example, produces JVM bytecode, which requires a JVM to be run. And TypeScript's compiler outputs JavaScript.