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Time Narration
00:01 Welcome to the spoken tutorial on iterative calculations using Scilab.
00:07 I am using Scilab version 5.2 in Mac operating system
00:11 but these calculations should work in other versions and also in Scilab that runs in Linux and Windows.
00:17 I will use the code available in the file 'iteration.sce'.
00:22 I have opened this file using Scilab editor which I plan to use only as an editor.
00:29 Let us create a vector using the colon operator. 'i' is equal to 1 colon 5,
00:38 creates a vector from 1 to 5, in increments of 1.
00:42 In this command, 'i' is equal to 1 colon 2 colon 5.
00:51 We see that the middle argument of 2 indicates the increment.
00:56 1 is the first argument where the vector starts. 'i' cannot go beyond 5,
01:01 it can be equal to 5, however.
01:04 Note that if the ending argument changes to 6 the result remains the same.
01:09 It is not difficult to explain this behavior.
01:13 Can you think for a moment why this happens?
01:15 We will now demonstrate the use of the for statement to perform iterative calculations.
01:22 for i is equal to 1 colon 2 colon 7 disp i end of for loop.
01:28 I will cut this, paste in Scilab console, press Enter.
01:34 This code prints out 'i' as we go through the loop.
01:37 The display is due to the command disp - the passed argument is displayed.
01:42 Recall that the for loop is used for integer values.
01:45 In this case, four integer values, namely, 1, 3, 5 and 7 are displayed.
01:50 The number of times the iterations take place is known as priori in for loops.
01:56 In the rest of this tutorial, we will stick to the default increment of 1.
02:01 Let us begin with the loop that displays 'i' equal to 1 to 5.
02:10 We will modify this code by introducing the break statement.
02:18 Note that 'i' is displayed only up to 2.
02:22 The iteration is not carried out till the last value of i, namely 5.
02:27 When i is equal to 2, the if block is executed for the first time.
02:30 The break command, however, terminates the loop.
02:34 If we want to get out of a loop when some intermediate condition is satisfied, we can use the break statement.
02:40 Note that "i is equal to 2" statement uses the "equal to" sign twice.
02:45 This is the standard way to compare the equality in programming languages.
02:50 The result of this comparison statement is a Boolean: true or false.
02:56 We will introduce the continue statement here, paste, press Enter.
03:06 This results in 'i' getting displayed only for 4 and 5.
03:10 For 'i' less than or equal to 3, as given by the i less than or equal to 3 statement, nothing happens.
03:18 The continue statement makes the program skip the rest of the loop.
03:22 Unlike the break statement, however, it does not exit the loop.
03:25 The parameter 'i' is incremented and all the calculations of the loop are executed for the new i.
03:32 We take a small break and show how to get help for operators of the type 'less than or equal to' (<=).
03:38 Let us type 'less than or equal to with help'.
03:46 This opens the Scilab Help Browser.
03:51 We see that the help is available under the option less.
03:56 So now after closing this, we type help less.
04:06 We see the required help instructions here. I will close this.
04:11 The for statement in Scilab is more powerful than in programming languages.
04:16 For example, let us perform a loop over a vector:
04:24 This script displays all values of 'v'.
04:28 Until now we have been displaying only the variables.
04:32 We can indeed display the result of a calculation as well.
04:35 The following code displays the square of the numbers.
04:44 We have spent quite a bit of time explaining the for loop.
04:48 Let us now move on to the while loops.
04:50 The while statement allows us to perform a loop when a Boolean expression is true.
04:55 At the beginning of the loop, if the expression is true,
04:58 the statements in the body of the while loop are executed.
05:02 If the program is written well, the expression becomes false and the loop is ended.
05:08 Now let us see an example for the while loop:
05:15 The values of 'i', from 1 to 6 are displayed.
05:19 Break and continue statements inside the while loop work exactly as they did in the for loop as we demonstrate using break:
05:33 We can see that the moment 'i' becomes equal to 3, the program exits the loop, thanks to the break statement.
05:39 You can also try the example for continue statement in while loop.
05:44 This brings us to the end of this spoken tutorial on iterative calculations using Scilab.
05:50 Spoken Tutorials are part of the Talk to a Teacher project, supported by the National Mission on Education through ICT.
05:57 More information on the same is available at the following link [1].
06:00 Thanks for joining. Good bye.

Contributors and Content Editors

Gaurav, PoojaMoolya, Sandhya.np14, Sneha