C Programming language

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.

# Passing pointers to functions in C

#include <stdio.h>
 
/* function declaration */
double calAverage(int *ary, int sz);
 
int main ()
{
   /* an int array with 5 elements */
   int price[5] = {1000, 2, 3, 17, 50};
   double ag;
 
   /* pass pointer to the array as an argument */
   ag = calAverage( price, 5 ) ;
 
   /* output the returned value  */
   printf("Average value is: %f\n", ag );
    
   return 0;
}

double calAverage(int *ary, int sz)
{
  int    i, sum = 0;       
  double ag;          
 
  for (i = 0; i < sz; ++i)
  {
    sum += ary[i];
  }
 
  ag = (double)sum / sz;
 
  return ag;
}