Simple Looping

• Most interesting programs need to do more than just execute from beginning to end.

• Think of processes that repeat (or have parts that repeat)

  • Grading papers

  • Baking cookies

  • Playing football

  • Shampooing your hair :-)

  • A pacemaker

  • Video games (play again?)

  • Anti-lock breaks

• To repeat a statement or group of statements in a C++ program we use the "while" statement.

• Syntax:  while (boolean-expression) statement;

• Example:  The code below write "tick" to the screen 3 times.

counter = 3;

while (counter > 0) {

    cout << "tick ";

    counter = counter - 1;  // could write counter--;

}

• Parts of a proper loop:  ITEM
  • I -- Initialize:  be sure to initialize your loop control variable *before* entering the loop
  • T -- Test:  the boolean expression in the while loop should test the loop control variable in some fashion
  • E -- Execute:  if the loop is to do anything useful, there will usually be some statements to execute
  • M -- Modify: if the loop control variable is not modified, then the loop will never terminate
• Code Examples:
  • clock.cpp
  • infinite.cpp