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In this video, we'll learn
about infinite loops.

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An infinite loop is often
called an endless loop.

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An infinite loop is a loop whose
control expression always evaluates

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to true, so it iterates over and over.

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Usually, infinite loops are
mistakes by the programmer.

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If you have an infinite loop,
it's pretty easy to know since

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the program does something or
does nothing over and over again.

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So we find and fix the problem.

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However, sometimes infinite loops
are written as infinite loops on

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purpose, and programmers use break
statements as strategic places to

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eventually break out of the loop.

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There are cases where this makes
sense and could be justified.

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However, writing an infinite loop
and using break statements to

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terminate the loop is usually bad
practice and should be rewritten

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so the loop condition expression is
descriptive of what the loop is doing.

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Here are a couple of examples
of infinite loops that are

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appropriate and in fact necessary.

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Infinite event loops are commonly
used in event-driven programs

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such as those you find on mobile
devices and embedded systems.

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In these programs, the program
loops forever listening for mouse

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clicks, mouse movements, touches
and so forth and reacting to them.

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This continues as long as
the program is running.

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Another example of an endless
loop is an operating system.

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An operating system is constantly
looping handling input/output,

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handling resources and so forth.

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It only shuts down when you
shut down your computer.

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Let's see a few examples
of infinite loops in c++.

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First, let's look at
an infinite for loop.

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Remember that all three expressions
in the for loop are optional.

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So if you omit all three,
you get just two semicolons.

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By definition in c++
that's an infinite loop.

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The output statement will be displayed
as long as the program is running.

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Let's look at a while loop.

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Here's an example of
an infinite while loop.

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It's probably exactly
what you were thinking of.

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While true will always be true.

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And the output statement will
execute over and over again.

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Of course, we don't have
to use the true keyword.

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We can use an expression
that's always true.

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So if we say while 10 is less than
12, since 10 is always less than 12,

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it'll loop forever, you get the idea.

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Finally, let's look at an
infinite do while loop.

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Again, the loop condition
will always be true.

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So the output statement
repeats forever.

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Okay, so what.

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Why would i ever do this?

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Well, you might write an event loop
like this but more often you see code

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that looks more like the following.

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Note that in this example, we
have an infinite loop since

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while true will always be true.

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However, we have a strategically
placed break statement

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that terminates the loop.

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Let's walk through the example.

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Inside the loop, we declare a
character variable named again.

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We ask the user if they want a loop
again and read the response as a

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character into the variable again.

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If again is uppercase n or
lowercase n, then we break

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and terminate the loop.

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If they enter anything
else, we loop again.

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This is an example of an
endless loop that might be okay.

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However, best practice suggests that
the loop condition be more informative

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of when the loop iterates if.

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I was doing the code review
of this code, I would

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refactor it to do just that.

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However, you do see code like this out
there, and now you know how it works.

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That completes this video.

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In the next video, we'll see how we
can nest loops one within the other.