A quick example using pointers and printf in C.

pointers.c

/*

Copyright (c) 2014 Doug Anger. This work is licensed under the Creative Commons
Attribution 4.0 International License. To view a copy of this license, visit
http://creativecommons.org/licenses/by/4.0/.

*/

#include <stdio.h>
int main(){

    int x;

    // Declaring an int reserves the needed amount of RAM to hold that int. That
    // memory has a unique address, which we can access with the & operator. The
    // opposite of & is *, which designates a pointer, so we can go ahead and
    // create a pointer to x even before we assign it a value.

    int* y = &x;

    // This is a pointer to x's location in memory. The * makes it a pointer.
    // Now let's go ahead and assign a value to x, so we can see how it works.

    x = 15;

    // Now we'll see how the % symbol works in printf. The % symbol is followed
    // by a letter or letters that specify what kind of variable to expect.

    // printf uses %i to format an int, passed in the next argument:

    printf("int x = %i. (We can print more stuff here.)\n", x);

    // This will print everything in quotes until it gets to the % character. At
    // that point it will format the variable passed in the next argument. Then
    // it will continue printing what we typed in quotes, including the newline,
    // represented by \n.

    // Showing how printf uses %lu to format a long unsigned int:

    printf("int* y = %lu (the memory address of x.)\n", (unsigned long int) y);

    // We coerced y into a long unsigned int because a regular int can't hold a
    // large enough value to address every location in RAM.

    // Showing how pointers work by printing x using the pointer *y:

    printf("int x = %i\n", *y);

    // The * and & operators are opposites. Just as &x gives us the memory
    // location of x, *y gives us the data stored at the memory location y. This
    // becomes a very useful way to pass variables into functions in a way that
    // allows the function to modify that original variable.

    // Now we return 0 to tell the OS that we are exiting normally. A non-zero
    // value would mean that we exited because of an error.

    return 0;

}