Full transcript
0:00Greetings , friends . My name is Sergey ,
0:02and we are continuing to learn
0:03programming using the C ++ language .
0:06Our topic for today will be the break
0:08keyword . We will talk about what it is ,
0:11why it is needed , and how to use it . So
0:13, to study the break keyword , we will
0:16need our code from the last lesson . If
0:19you haven't watched it , be sure to
0:21watch it . In that very lesson , I showed
0:24a certain feature of the for loop where
0:27it acts as an infinite loop . And it is
0:30precisely to solve this problem that we
0:33need the break keyword . Before we start
0:36solving this problem , let's recall what
0:38we had there and see what code we have
0:41now . I modified it a little bit to make
0:44it more illustrative . Let's run it
0:46first , and with the code running , I
0:48will explain to you what's what . So , on
0:51line eleven and line eighteen , we have
0:53two inscriptions . These are the start
0:55of the loop and the end of the loop .
0:56This is so that in the console , at the
0:59start and end of the loop , we can
1:01clearly see that it has begun and ended
1:03. And we also have the for loop itself .
1:06And it works as long as the variable i
1:09is less than 10 . Under this condition ,
1:13our loop runs 10 times and completes
1:16successfully . But in the last lesson , I
1:19told you that this part of the for loop
1:21is optional . That is , without it , it
1:26will also work , but it will act as if
1:29it is always true here . In that case ,
1:33our loop will run infinitely . Let's
1:36take a look . So , we won't see the end
1:39of the loop . Likewise , if we remove it
1:41from here , it makes no difference . This
1:45thing works in the exact same way . And
1:48it is in this case that we can clearly
1:51see how the break keyword works . To see
1:54how it works , we will need a condition
1:58that performs some kind of check . Let's
2:02say we now have a simple condition that
2:05will simply check our variable i , which
2:08is also the control variable of our
2:11loop , our loop iterator , for equality
2:14with five . If our condition in the if
2:18statement is met , that is , if the
2:20variable i equals five , we will enter
2:23the body of the loop . Right here , we
2:25can write the break keyword . What will
2:29happen in this case ? In this case , we
2:32will exit the loop . So , the break
2:35keyword is used to interrupt the
2:37execution of a loop and exit it . That
2:40is , before any condition that could
2:43have been placed here is met . In this
2:46case , the condition in the loop itself
2:48is always true , so it’s an infinite
2:49loop , as I’ve already shown you . But
2:52by using the " break " keyword with this
2:55check for five , we can exit the loop .
2:58Let's run our program and see more
3:00clearly what happens here . So , as soon
3:04as the variable i in our loop became
3:06equal to five , this condition became
3:09true , we went inside , hit the " break "
3:12keyword , and exited . Our program
3:16continued to execute outside the loop .
3:18Thus , once again , the " break " keyword
3:20is used to interrupt the execution of a
3:23loop under specific conditions . We can ,
3:26in principle , leave our " i is less than
3:28" condition here , right ? What is going
3:31on ? " i is less than 10 " . Let's comment
3:35out this part of the code for now .
3:38Let’s run it again . So , now our loop
3:44runs as long as our variable i is less
3:46than 10 , executing 10 times . But if we
3:50uncomment the condition with our " break
3:54" keyword and run our program again ,
3:57our loop will still only run five times
4:01. Note that although in the loop
4:06condition our variable i could reach 10
4:09, this condition was met sooner ,
4:12meaning i became five before this
4:14condition was fulfilled . We entered the
4:18if statement , the " break " keyword was
4:20executed , and we exited , we exited the
4:23loop . To help you understand : it's a
4:27simple condition here , but there could
4:30be a lot of code , and your loop should
4:33run until , say , once in a million years
4:37, a specific condition is met that
4:39returns true , and then you break out of
4:43the loop . This way of working is also
4:46possible . The " break " keyword works the
4:49same way with " while " loops and " do
4:51while " loops . I will show you with a "
4:54while " example . So , our " while " loop
4:56condition will be true . Meaning the
4:58condition in the parentheses will
5:00always be true . We’ll just set it to
5:01true directly . Therefore , our loop will
5:04run indefinitely . Let’s comment out
5:06this part of the code . So it won’t be
5:09executed right now . It’s simply not
5:11here . I’ll probably just delete it
5:12from here . Move it somewhere else ,
5:15right ? Paste it like this . We’ll only
5:19need this bit of text . Okay , that’s
5:21it . We don’t need this part . In this
5:23case , our loop will run indefinitely .
5:29True , we don’t have an i variable in
5:31our " while " loop , so we need to create
5:33it . We’ll create it right now .
5:36Initialize it to zero . And we’ll also
5:40add an increment here so it increases
5:43with every iteration of the loop .
5:47Basically , this construction is almost
5:49the same as what we had with the for
5:50loop , just written a little differently
5:52. Let's run it . It works exactly the
5:55same way , meaning it is looped . And
5:58here we can also add our check to see
6:02if variable a is equal to , let's say ,
6:06six now . Alright . And if our variable i
6:11becomes equal to six , then we will exit
6:14the loop thanks to the break keyword .
6:17Let's take a look . Well , that is
6:20exactly what happened . Only we see the
6:25message variable i = 5 here , not
6:28variable i = 6 . Because first , we
6:32printed the record with our variable i
6:36when it was equal to five . Then
6:38variable i increased by one thanks to
6:41the increment . And we entered this
6:43condition . So the variable i was
6:45already equal . Therefore , we exited the
6:47loop , and the record that our variable
6:50i is already 6 was not displayed . That
6:52is roughly how it works . In a while
6:54loop , it is the same . Also , the break
6:56keyword works not only with loops .
6:59Perhaps , if you watched my previous
7:02videos carefully , you remember I had a
7:05lesson about the Switch structure , and
7:08there were also case and default blocks
7:11that also worked with the break
7:13operator . But I won't repeat myself
7:16here now . If you haven't seen that
7:19video , then at the end of this video
7:21there will be a link to it . And also in
7:23the description below this video , I
7:25will leave a link to it as well . You
7:26can take a look . I explain everything
7:28in detail there . Well , actually , that's
7:30all I have for now . If you liked this
7:32video , if it was useful and interesting
7:34to you , then hit the like button . And
7:36also subscribe to the channel if you
7:37haven't yet , so you don't miss the next
7:39lessons . Thank you all for your
7:41attention . Bye . M.