1. Looping ROBERT REVAES

2. Logical Operators  && AND  Both have to be true for it to evaluate to be true.  || OR  One or the other has to be true for it to evaluate to be true.  ! NOT  Returns the opposite result.

3. Testing the State of an I/O Stream  C++ provides a way to check whether a stream is in the fail state.  ifstream myIn;  myIn.open(“measures.dat”);  if(!myIn) {  cout << “Can’t open the input file.”;  return 1;  }

4. The While Statement  Loop executes the same statement over and over, as long as a condition or set conditions is satisfied.  while( Expression)  Statement  Ex:  while (inputVal != 25)  cin >> inputVal;  The statement to be executed each time through the loop is called the body of the loop.

5. Phases of Loop Execution  The body of a loop is executed in several phases:  The moment that the flow control reaches the first statement inside the loop body is the loop entry.  Each time the body of a loop is executed, a pass is made through the loop. This pass is called an iteration.  Before each iteration, control is transferred to the loop test at the beginning of the loop.  When the last iteration is complete the flow of the control has passed to the first statement flowing the loop, the program has exited the loop.  The condition that causes a loop to be exited is the termination condition.

6. Loops  Two major types of loops:  count-controlled  Repeat a specified number of times.  event-controlled loops  Repeat until something happens within the loop.

7. Count-Controlled Loops  Uses a variable we call the loop control variable in the loop test.  Ex:  int loopCount = 1;  while (loopCount <= 10) {  cout << “Hello!” << endl;  loopCount++;  }  Variables used in the way loopCount is used are called counters.

8. Event-Controlled Loops  Several kinds of event-controlled loops exist:  sentinel controlled  Some special value that that will never show up in normal input.  end-of-file controlled  After a program has read the last piece of data from an input file, it’s in a successful state.  flag controlled  A Boolean variable that tis used to control the logical flow of a program.

9. Looping Subtasks  Three common tasks:  counting  Keep track of the number of times the loop has been executed.  summing  Sum a set of data values.  keeping track of a previous value  Remember the previous value that was read from input.