Difference between revisions of "PHP-and-MySQL/C2/Loops-While-Statement/English-timed"
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|00:00 | |00:00 | ||
− | |Hello and welcome. | + | |Hello and welcome. I have decided to create separate tutorials for each looping statement. |
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|00:07 | |00:07 | ||
− | |I want to keep it simple. This will be useful as a reference also if you need to refer to how a particular loop works. | + | |I want to keep it simple. This will be useful as a reference also if you need to refer to how a particular '''loop''' works. |
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|00:17 | |00:17 | ||
− | |In this tutorial, we will learn about the | + | |In this tutorial, we will learn about the '''while''' loop. |
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|00:21 | |00:21 | ||
− | |A | + | |A '''while''' loop checks for a '''condition''' at the start of the loop and executes the code depending on whether this '''condition''' is '''True''' or not. |
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|00:38 | |00:38 | ||
− | | | + | |For example, I'll start my '''while''' loop here and this is the '''condition''' and this is my '''block'''. |
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|00:51 | |00:51 | ||
− | |I'll represent my block between curly brackets. | + | |I'll represent my '''block''' between curly brackets. |
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|00:56 | |00:56 | ||
− | |My condition is here. Now, in the ' | + | |My '''condition''' is here. Now, in the '''if''' statement, for example I used 1==1. |
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|01:04 | |01:04 | ||
− | |Now if I say 'test' or 'loop' here. | + | |Now, if I say 'test' or 'loop' here. |
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|01:07 | |01:07 | ||
− | |This is a loop here and then a break. Now what happens is as long as 1=1, it would create a loop | + | |This is a '''loop''' here and then a break. Now what happens is as long as 1=1, it would create a loop. |
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|01:17 | |01:17 | ||
− | |If I do something here, | + | |If I do something here, let's try this. |
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|01:22 | |01:22 | ||
− | |It would probably crash your browser because the loop would be repeated as long as 1=1 and for infinite no. of times, 1 will always equal 1. | + | |It would probably crash your browser because the '''loop''' would be repeated as long as 1=1 and for infinite no. of times, 1 will always equal to 1. |
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|01:34 | |01:34 | ||
− | |So since the loop will always be repeated, your browser will crash. | + | |So, since the '''loop''' will always be repeated, your browser will crash. |
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|01:40 | |01:40 | ||
− | | | + | |Let's say '''while''' a variable 'num' is smaller or equal to 10 and under '''echo''' I can say - '''num ++'''. |
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|01:57 | |01:57 | ||
− | | '++' is an arithmetical operator. And what it basically does is, it increases num by 1. It is the same as writing 'num =num +1' | + | | '++' is an arithmetical '''operator'''. And what it basically does is, it increases 'num' by 1. It is the same as writing 'num =num +1'. |
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|02:16 | |02:16 | ||
− | |So it takes num and says that it is equal to the value of num plus 1. | + | |So, it takes 'num' and says that it is equal to the value of 'num plus 1'. |
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|02:23 | |02:23 | ||
− | |So this again is an arithmetical operator. What's going to happen is - | + | |So, this again is an arithmetical operator. What's going to happen is - |
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|02:29 | |02:29 | ||
− | | | + | |we are going to say 'num' less than or equal to (<=) 10; if 'yes' then '''echo''' loop and then say add 1 on to the variable 'num'. |
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|02:41 | |02:41 | ||
− | |But what we should really do is create 'num = | + | |But, what we should really do is create 'num = 1' at the moment. So '''loop''' once at 1. This will then equals to 2, then 3, then 4 all the way up to 10 and then it will stop. |
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|03:01 | |03:01 | ||
− | |After that the rest of the code below this will continue. | + | |After that, the rest of the code below this will continue. |
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|03:06 | |03:06 | ||
− | |So we said this 1 and see what will we get. Okay we got a loop 1,2,3,4,5,6,7,8,9,10 times | + | |So, we said this 1 and see what will we get. Okay we got a loop 1,2,3,4,5,6,7,8,9,10 times. |
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|03:20 | |03:20 | ||
− | |Now to make it more fun I'll say loop 1 and I'll concatenate 'num' to the end of that | + | |Now to make it more fun, I'll say '''loop''' 1 and I'll concatenate 'num' to the end of that. |
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|03:27 | |03:27 | ||
− | |In fact let's make it simpler and say 'num' inside - it will make it much easier to read | + | |In fact, let's make it simpler and say 'num' inside - it will make it much easier to read. |
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|03:37 | |03:37 | ||
− | |Okay I'll say loop 1 and add 1 and then I'll say loop 2 and I'll add another 1; that's loop 3 add another 1 up to 10. | + | |Okay. I'll say '''loop 1''' and add 1 and then I'll say loop 2 and I'll add another 1; that's loop 3 add another 1 up to 10. |
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|03:49 | |03:49 | ||
− | | | + | |Let's open this up. '''Refresh''' it. There you go. You got loop 1,2,3 all the way up to 10 as you can see. |
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|03:58 | |03:58 | ||
− | | | + | |Let's change this value here to 100. '''Refresh''' that. You can see it has gone to hundred. The bigger the number, the longer it will take to loop. |
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|04:08 | |04:08 | ||
− | |Let's take 6000. Let's refresh that. It's going to take a while. There you go - up to 6000. So it's very efficient in this way | + | |Let's take 6000. Let's '''refresh''' that. It's going to take a while. There you go - up to 6000. So it's very efficient in this way. |
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|04:20 | |04:20 | ||
− | |You can try combining this with an 'array' to create a program that echoes out of the alphabet inside the 'array' | + | |You can try combining this with an '''array''' to create a program that echoes out of the alphabet inside the '''array'''. |
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|04:27 | |04:27 | ||
− | |You can use loops to echo out every single value of an array | + | |You can use '''loops''' to '''echo''' out every single value of an array. |
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|04:32 | |04:32 | ||
− | |Just give it a go. I will probably do this in one my tutorial - not in the basics section though | + | |Just give it a go. I will probably do this in one of my tutorial - not in the basics section though. |
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|04:40 | |04:40 | ||
− | |However, this is the | + | |However, this is the basic structure. What I also recommend you to do is, create a variable here called 'max' and put your maximum value here. |
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|05:03 | |05:03 | ||
− | | | + | |if you have more than 1 loop. I prefer it for readability and flexibility for my program. Okay. So, that's a '''while''' loop. Let me summarize. It checks the '''condition''' of the start. |
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|05:17 | |05:17 | ||
− | |If the condition is True | + | |If the condition is '''True''' it would execute this '''block''' of '''code''' and you can do things like 'echo alpha'. |
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|05:24 | |05:24 | ||
− | |Your variable is being incremented. Make sure that you do increment your variable otherwise it will loop for infinity. | + | |Your variable is being incremented. Make sure that you do increment your variable otherwise it will '''loop''' for '''infinity'''. |
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|05:32 | |05:32 | ||
|Thanks for watching. This is Sidharth for the Spoken Tutorial Project, signing off. Goodbye. | |Thanks for watching. This is Sidharth for the Spoken Tutorial Project, signing off. Goodbye. |
Revision as of 21:49, 20 May 2015
Time | Narration |
00:00 | Hello and welcome. I have decided to create separate tutorials for each looping statement. |
00:07 | I want to keep it simple. This will be useful as a reference also if you need to refer to how a particular loop works. |
00:17 | In this tutorial, we will learn about the while loop. |
00:21 | A while loop checks for a condition at the start of the loop and executes the code depending on whether this condition is True or not. |
00:38 | For example, I'll start my while loop here and this is the condition and this is my block. |
00:51 | I'll represent my block between curly brackets. |
00:56 | My condition is here. Now, in the if statement, for example I used 1==1. |
01:04 | Now, if I say 'test' or 'loop' here. |
01:07 | This is a loop here and then a break. Now what happens is as long as 1=1, it would create a loop. |
01:17 | If I do something here, let's try this. |
01:22 | It would probably crash your browser because the loop would be repeated as long as 1=1 and for infinite no. of times, 1 will always equal to 1. |
01:34 | So, since the loop will always be repeated, your browser will crash. |
01:40 | Let's say while a variable 'num' is smaller or equal to 10 and under echo I can say - num ++. |
01:57 | '++' is an arithmetical operator. And what it basically does is, it increases 'num' by 1. It is the same as writing 'num =num +1'. |
02:16 | So, it takes 'num' and says that it is equal to the value of 'num plus 1'. |
02:23 | So, this again is an arithmetical operator. What's going to happen is - |
02:29 | we are going to say 'num' less than or equal to (<=) 10; if 'yes' then echo loop and then say add 1 on to the variable 'num'. |
02:41 | But, what we should really do is create 'num = 1' at the moment. So loop once at 1. This will then equals to 2, then 3, then 4 all the way up to 10 and then it will stop. |
03:01 | After that, the rest of the code below this will continue. |
03:06 | So, we said this 1 and see what will we get. Okay we got a loop 1,2,3,4,5,6,7,8,9,10 times. |
03:20 | Now to make it more fun, I'll say loop 1 and I'll concatenate 'num' to the end of that. |
03:27 | In fact, let's make it simpler and say 'num' inside - it will make it much easier to read. |
03:37 | Okay. I'll say loop 1 and add 1 and then I'll say loop 2 and I'll add another 1; that's loop 3 add another 1 up to 10. |
03:49 | Let's open this up. Refresh it. There you go. You got loop 1,2,3 all the way up to 10 as you can see. |
03:58 | Let's change this value here to 100. Refresh that. You can see it has gone to hundred. The bigger the number, the longer it will take to loop. |
04:08 | Let's take 6000. Let's refresh that. It's going to take a while. There you go - up to 6000. So it's very efficient in this way. |
04:20 | You can try combining this with an array to create a program that echoes out of the alphabet inside the array. |
04:27 | You can use loops to echo out every single value of an array. |
04:32 | Just give it a go. I will probably do this in one of my tutorial - not in the basics section though. |
04:40 | However, this is the basic structure. What I also recommend you to do is, create a variable here called 'max' and put your maximum value here. |
04:53 | This will do exactly the same thing. It's just a lot more easy to read and you can declare all this here and this would be a reference to it |
05:03 | if you have more than 1 loop. I prefer it for readability and flexibility for my program. Okay. So, that's a while loop. Let me summarize. It checks the condition of the start. |
05:17 | If the condition is True it would execute this block of code and you can do things like 'echo alpha'. |
05:24 | Your variable is being incremented. Make sure that you do increment your variable otherwise it will loop for infinity. |
05:32 | Thanks for watching. This is Sidharth for the Spoken Tutorial Project, signing off. Goodbye. |