A pointer in C is a variable that holds the address of another
  variable.  Pointers are declared with the asterisk operator.  For
  example:

       int i, *ip, *np;       /* i IS AN INTEGER, ip AND np ARE
                                 POINTERS TO INTEGERS           */

       The following operations are permitted on pointers:

       o  Assigning an address to the pointer (as in ip = &i;)

       o  Fetching the object of the pointer (by dereferencing the
          pointer) with the asterisk operator (i = *ip;, which
          assigns the addressed integer to i)

       o  Adding (as in ip += 5;, which makes ip point to the object
          that is five longwords away from the initial address in ip)

       o  Subtracting (as in i = np - ip;, which gives the number of
          objects separating the objects pointed to by np and ip)