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Pointers to Functions

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The function pointer is a powerful feature in c. In memory a function has a physical location that can be assigned to a pointer. This address is the entry point of the function and it is the address used when the function is called. Once a pointer points to a function, the function can be called through that pointer. Function pointers also allow functions to be passed as arguments to other functions or function pointers is a pointers, that point to the address of a function.

Now we can se that when we run the any program than that running program gets a certain space in the main-memory. than the executable compiled program code and variables are put inside this memory. Thus that program code have a functions than that function in the program code is, like e.g. a character field, nothing else than an address. It is only important how you, or better your compiler/processor, interpret the memory a pointer points to.

#include<stdio.h>
#include<conio.h>
void my_int_func(int x)
{
    printf( "%d\n", x );
}
int main()
{
    void (*yes)(int);
    yes = &my_int_func;
/* call my_int_func (note that you do not need to write (*yes)(2) ) */
    yes( 2 );
    /* but if you want to, you may */
    (*yes)( 2 );

    return 0;
};

Output: The output of the above program would be:

2 2

Example

#include<stdio.h>
   #include<conio.h>
   int show();
   void main()
   {
   int (*fP)();
   clrscr();
   fP=show;
      printf("Address of function :%u",show);
       (*fP)();
       getch();
   }

   int show()
   {
   printf("\nFunction called using pointer!");
   return 0;
   }

Output: The output of the above program would be:

Address of function : 694

Function called using pointer!

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