Basics of C/C++: Part III--Loops

Submitted on: 1/1/2015 7:23:00 AM
By: Alexander of (from psc cd)  
Level: Beginner
User Rating: By 5 Users
Compatibility: C, C++ (general)
Views: 2083
     This is the third installment of the Lessons in C programming tutorials created by me, Alexander. In this lesson I will cover loops. Loops basically do what it sounds like, loop. If you have read lesson 2 you should understand some Boolean expressions. If you do not, you should read it again. When working with loops it is important to understand truth and false. Maybe you should try doing some truth tables with problems.


There are basically 3 types of loops. FOR, WHILE, DO WHILE Each of them has their uses.  They are all outlined below.

     FOR - FOR loops are the most useful type, I believe. The layout is for(variable initialization, conditional, incrementing variable) It is very versatile, and the layout can be changed somewhat. Basically, the variable initialization allows you to either declare a variable and give it a value, or give a value to another variable. Second, the conditional statement. What it does is it says that while the conditional is true then it would do what in is in the body. Third, the incrementing variable section. It does not have to increment a variable. It can decrement, which is subtracting one, or it can perform various other manipulations on the variable.

Ex. #include <iostream.h> //We only need one header file

void main() //We always need this

//The loop goes while x<100, and x has one

for(int x=0;x<100;x++)/*THE LOOP*/ //added to it every time the loops


cout<<x<<endl; //Outputting x



     This program is a very simple example of a for loop. x is set to zero, while x is less than 100 do cout<<x<<endl; add 1 to x until the loop ends. Pretty simple to understand, but it is a very powerful loop, and much better than WHILE and DO WHILE loops.

     WHILE - WHILE loops are very simple, but not as useful as FOR loops. The basic structure is...WHILE(true) then do whatever is in the body. The truth could be x==1 or while(x!= 7)  (x does not equal 7)

Ex. #include <iostream.h> //We only need this header file

void main() //Of course...

{ int x=0; //Don't forget to declare variables

while(x<100) //While x is less than 100 do


cout<<x<<endl; //Same output as the above loop

x++; //Adds 1 to x every time it repeats



     This was another pretty simple example, but it is longer than the above FOR loop, showing why I like for better than while, though while is a very easy loop to use, so if you are having trouble then you can use it, but try to use for.

     DO WHILE - DO WHILE loops are useful for only things that want to loop at least once.  Basically it goes DO { THIS } WHILE(TRUE) Now, it is your turn to try and do a loop! make a DO WHILE loop that does what the above programs do...output 0 to 99! It is not hard, if you have trouble email me at and I will give you some help... Best of luck :)

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