The arguably best exercise for loops is printing
various patterns (using just putchar(c) with
c='*', ' ' or '\n') here given in the order of increasing
difficulty and assuming you first generalize them to
size n. After this you either write simple loops
with virtuosity or you better find another fun.


****
****
****
****

*
**
***
****

   *
  **
 ***
****

****
*  *
*  *
****

****
  *
 *
****

  *
 ***
*****
 ***
  *

  *
 * *
*   *
 * *
  *

*   *
 * *
  *
 * *
*   *

* * *
 ***
*****
 ***
* * *