Similarities and differences between pointers and arrays in C

This is an example C program which demonstrates similarities and differences between pointers and arrays.

#include <stdio.h>

int main ()
{
    /* x is an array of "int" of size 10. */
    int x[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    /* y is a pointer to "int". */
    int * y;

    y = x;

    /* Print information about y. */

    printf ("Size of y = %d\n", sizeof (y));
    printf ("Contents of y = %p\n", y);
    printf ("Address of y = %p\n", & y);
    printf ("*y = %d\n", *y);
    printf ("y[1] = %d\n", y[1]);
    printf ("2[y] = %d\n", 2[y]);

    /* Print information about x. */

    printf ("Size of x = %d\n", sizeof (x));
    printf ("Contents of x = %p\n", x);
    printf ("Address of x = %p\n", & x);
    printf ("*x = %d\n", *x);
    printf ("x[1] = %d\n", x[1]);
    printf ("2[x] = %d\n", 2[x]);

    return 0;
}

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The output of the example looks like this:

Size of y = 4
Contents of y = 0xbfbfe8a0
Address of y = 0xbfbfe89c
*y = 1
y[1] = 2
2[y] = 3
Size of x = 40
Contents of x = 0xbfbfe8a0
Address of x = 0xbfbfe8a0
*x = 1
x[1] = 2
2[x] = 3

The sizes and addresses printed will vary for different computers. Notice that the contents of the pointer y and the address of y are different, but for the array x they come out the same. The size of y is four bytes, but the size of x is forty bytes.


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