Lesson 3

LOOP: DOING IT OVER AND OVER 

LOOP AS A LABOR FORCE

One of the strengths of the computer is its ability to repeat a process over and over without getting tired or threatening to strike. The program that you have written to perform a single task can now be repeated to perform the same task as many times as you wish. This process of going over and over is known as repetition and is called a loop. Can you think of a loop? Of course! Our everyday activities, including getting up, eating, working, studying, and sleeping are examples of a loop. Can you identify other loops?  With a little thought, I know you can.  

COMPUTERS IN THE LOOP

Did you know that your computer is in a constant cycle of input, process, and output? This constant cycle of input, processing, and output means that your computer is in a loop. It waits for you to enter data, takes your input, analyzes it, performs the required task, and finally displays the result. We can generalize and say that every automated system, from the bank ATM machine, supermarket pricing, through the search engine of the Internet all use the loop. 

WHAT DO YOU NEED TO MAKE A LOOP?  

It is very simple to create a loop. Just follow these three steps:

1)      Use a reserved word (construct) from the C/C++ language to tell the program    to loop.

2) Set a condition as to whether to continue or to terminate the loop.

3) Set aside the body of a loop to determine what you want to loop.  

C/C++ LOOP CONSTRUCTS  

There are various ways to loop in a program, and for each way there is a construct (reserve word) from C/C++ that instructs the program to loop. These loop constructs are:

1)  while
2)  for
3)  do     while
4)  goto   label

Each of the above four loop constructs can do the same job. However, some are better suited in some situations and there are others that are rarely used, such as the goto.  For simplicity we will concentrate on the while command, and later the others will be introduced.
 

By going through the foundations of programming and languages you will find it easier to build programs from scratch using C/C++ in the chapters that follow.