What is the difference between marcos and functions in C?

Question

Are both comparisons same or different ?

Answer 1

The basic difference is that functions are compiled whereas macros are preprocessed. When you use a function call it will be translated into ASM CALL with all these stack operations to pass parameters and return values. When you use a MACRO, C preprocessor will translate all strings using macro, do the necessary replacement and than compile.

See the following example

#define square(x) x*x

int square1(int x) 
{
  return x*x;  
}

main()
{
   printf("Macro output - %d\n", square(2+2));
   printf("Function output - %d\n", square1(2+2)); 
}

Macro output - 8
Function output - 16

Now in case 1 square(2+2) is replaced with 2+2*2+2 and then code is compiled which gives output 8 and in case 2 square1(2+2) 2+2 is calculated at the compile time and passed to the function...

Answer 2

Macros are pre processed where as functions are compiled.. take a look at this
Macros
Functions