What is the difference between - 1) Preprocessor,linker, 2)Header file,library? Is my understanding correct?

Question

Okay, until this morning I was thoroughly confused between these terms. I guess I have got the difference, hopefully.

Firstly, the confusion was that since the prepr

Answer 1

This is an extremely common source of confusion. I think the easiest way to understand what's happening is to take a simple example. Forget about libraries for a moment and consider the following:

$ cat main.c
extern int foo( void );
int main( void ) { return foo(); }
$ cat foo.c
int foo( void ) { return 0; }
$ cc -c main.c
$ cc -c foo.c
$ cc main.o foo.o

The declaration extern int foo( void ) is performing exactly the same function as the header file of a library. foo.o is performing the function of the library. If you understand this example, and why neither cc main.c nor cc main.o work, then you understand the difference between header files and libraries.