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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 <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
lallain@concentric.net and I will give you some help...
Best of luck :) Check back again for
more programming in C!
#include <iostream.h>
int main()
{
int x=0;
do while(x<100)
{
cout << x << endl;
x++;
}
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