What is compiler, linker, loader?

Question

I wanted to know in depth meaning and working of compiler, linker and loader. With reference to any language preferably c++.

Answer 1

Wikipedia ought to have a good answer, here's my thoughts:

• Compiler: reads something.c source, writes something.o object.
• Linker: joins several *.o files into an executable program.
• Loader: code that loads an executable into memory and starts it running.

Answer 2

Hope this helps you a little more.

First, go through this diagram:

                         (img source->internet)

You make a piece of code and save the file (Source code), then

Preprocessing :- As the name suggests, it's not part of compilation. They instruct the compiler to do required pre-processing before the actual compilation. You can call this phase Text Substitution or interpreting special preprocessor directives denoted by #.

Compilation :- Compilation is a process in which a program written in one language get translated into another targeted language. If there is some errors, the compiler will detect them and report it.

Assemble :- Assemble code gets translated into machine code. You can call assembler a special type of complier.

Linking:- If these piece of code needs some other source file to be linked, linker link them to make it a executable file.

There are many process that happens after it. Yes, you guessed it right here comes the role of the loader:

Loader:- It loads the executable code into memory; program and data stack are created, register gets initialized.

Little Extra info :- http://www.geeksforgeeks.org/memory-layout-of-c-program/ , you can see the memory layout over there.

Answer 3

A compiler is a special program that processes statements written in a particular programming language and turns them into machine language or "code" that a computer's processor uses

Answer 4

compiler changes checks your source code for errors and changes it into object code.this is the code that operating system runs.

You often don't write a whole program in single file so linker links all your object code files.

your program wont get executed unless it is in main memory

Answer 5

• Compiler : Which convert Human understandable format into machine understandable format
• Linker : Which convert machine understandable format into Operating system understandable format
• Loader : is entity which actually load and runs the program into RAM

Linker & Interpreter are mutually exclusive Interpreter getting code line by line and execute line by line.

Answer 6

Compiler It converts the source code into the object code.

Linker It combines the multiple object files into a single executable program file.

Loader It loads the executable file into main memory.