#include <stdio.h>
#define TABLE_SIZE 11

void f (double p[TABLE_SIZE]){
  int i;

  for(i = 0; i < TABLE_SIZE; i++)
    p[i] = p[i] * 2;  // p is NOT a local copy of the actual parameter. 
                      // It is a pointer to the actual parameter array.
}

int main(void) {
  double a[TABLE_SIZE];
  int i;

  for(i = 0; i < TABLE_SIZE; i++)
    a[i] = 2*i;

  for(i = 0; i < TABLE_SIZE; i++)    /* 0 2 4 6 ... */
    printf("Before calling f: a[%d] = %f\n", i, a[i]);

  printf("\n");

  f(a);  // The elements of a are not copied to f.
         // Instead a pointer to the first element in a is passed to f.
         // OK - but maybe not as intended. Compiles and runs.

  for(i = 0; i < TABLE_SIZE; i++)    /* 0 4 8 12 ... */
    printf("After calling f: a[%d] = %f\n", i, a[i]);

  return 0;
}