Difference between revisions of "PHP-and-MySQL/C2/Loops-Do-While-Statement/English-timed"
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Revision as of 10:09, 21 May 2015
| Time | Narration |
| 00:00 | Welcome again! In this tutorial, we will learn the do-while loop. |
| 00:05 | It's also called the do-while statement. You can choose to call it a loop or a statement. |
| 00:12 | The base is similar to the while loop although the condition is checked at the END of the loop as opposed to the START. |
| 00:20 | We have do, our block with the curly brackets and while at the end. Then a condition in here. So, this is the condition. |
| 00:29 | Now I'm going to type a little program - I want the numbers to increment each time and echo on each line as I've done in my while loop. |
| 00:41 | Now the condition - when the number reaches 10, I want a variable called name to be changed to another name in which the loop will stop. |
| 01:00 | I'll type num = 1 to start with. |
| 01:04 | Then I'll type "my name is Alex". |
| 01:09 | The condition of the loop I want is - while the name = Alex. |
| 01:15 | As long as the name=Alex, this will loop. So, somewhere we need to say on a specific condition - change the name to "Billy" and then the loop won't continue any more because the name is not equal to "Alex". |
| 01:31 | Now, we will include an if statement inside the do loop. Remember: you can put
and there's really no limit to what you do. As long as your code works and flows properly and doesn't produce infinite values, you will be fine. |
| 01:55 | Now what we type is: do. |
| 01:57 | Firstly, echo out the value of the number. |
| 02:00 | You can concatenate that with a brief HTML code to break the line. |
| 02:05 | Here I type num++ which is the same as num +1. |
| 02:14 | Then my if statement - if num is greater than or equal to 10 then no echo. |
| 02:26 | I want to change the name to "Billy". |
| 02:30 | Let me recap. Remember, I'm not using curly brackets here because I have one line of code that needs to be executed in the block after the if statement. |
| 02:42 | Therefore I just need one line code because it looks neat. |
| 02:46 | So, let me recap what I've done. I've got the number set to 1. |
| 02:51 | This is my number variable, this can increment and can be echoed out to the user. |
| 02:57 | I've got my name set to "Alex". |
| 03:00 | We start our do. |
| 03:02 | The name is still "Alex". |
| 03:04 | There's no condition; so this will run regardless of anything. |
| 03;07 | So, we echo out the number which is 1. |
| 03:10 | We increment it by 1 which will equal to 2. |
| 03:14 | Now, we'll say if the number which is currently 2 is bigger than or equal to 10, (which it isn't) then continue through this. |
| 03:26 | It isn't. So skip this. It'll go on to say name = Alex. And then go back to the top. |
| 03:34 | This will still be 2. That means the loop is stuck at that block of code. |
| 03:41 | It'll echo out 2. |
| 03:43 | It'll add one and say 3. |
| 03:46 | And then it'll say: is 3 bigger than or equal to 10? |
| 03:51 | No, it's not. |
| 03:52 | So, the name is not changed to "Billy" instead it'll carry on with the rest of our code. |
| 03:58 | The name is still "Alex". |
| 04:00 | So, the loop continues on. In this case it will go on until it reaches 10 but 9 will be echoed out to the user. |
| 04:09 | Now num will become 10. |
| 04:11 | The if condition will be True. |
| 04:13 | The name would be set to "Billy" and in the while condition it doesn't equal "Alex". So the while loop will stop and the code down here will continue. |
| 04:25 | So, let's execute this code. Do our loop. Click on that. |
| 04:31 | OK, we've got 1, 2, 3 all the way up to 9. |
| 04:35 | Obviously, our condition has been met. Our name has changed to "Billy". Our name doesn't equal "Alex" anymore. |
| 04:43 | So, our loop here has stopped. |
| 04:45 | Now change the if to 11 or you can change num to 0. |
| 04:50 | Now this won't work and you'll see why. |
| 04:54 | We've got 0 to 9. |
| 04:57 | The reason being is your starting number. |
| 05:02 | What this will do is, like I said before, it'll echo out the current number, then changes it to an increment of 1 and then it'll compare it in the if statement. |
| 05:13 | So, you're comparing what you can't see. |
| 05:16 | If you change this to 11, you'll compare it to 11, then change it to "Billy" and then it'll end the loop. |
| 05:23 | We never see the value of 11, it's only an inside comparison. |
| 05:27 | If we refresh this, we can see there's 1 to 10 now. |
| 05:31 | That is basically the do-while loop. Even though they are pretty similar, the do-while loop is more useful than the while loop when you run into a programming sort of logic. It may be more useful in some cases. |
| 05:44 | So, practice this, try and enter some values. Also, try to recreate the program I've just created. |
| 05:52 | There will be more tutorials on loops shortly; so keep watching. |
| 05:56 | This is Anoushka, dubbing for the Spoken Tutorial project. |
