LESSON3.TXT

Lesson 3: Loops


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 //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< }
}


This program is a very simple example of a for loop. x is set to zero, while x is less
than 100 do cout<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 //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++; //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
lallain@concentric.net and I will give you some help... Best of luck :) Check back again for
more programming in C!

#include

int main()
{
int x=0;
do while(x<100)
{
cout << x << endl;
x++;
}
}

Note: My homepage is http://www.cprogramming.com. My email is lallain@concentric.net. Please
email me with comments and or suggestions. If you want to use this on your own site please
email me and add a link to http://www.cprogramming.com. Thanks :)

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