C-and-C++/C2/Increment-And-Decrement-Operators/English-timed

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Time Narration
00:01 Welcome to the spoken tutorial on Increment and Decrement Operators in C and C++.
00:08 In this tutorial, we will learn about:
00:10 Increment and decrement operators.
00:12 '++' eg. a++ which is postfix increment operator.
00:18 ++a which is prefix increment operator.
00:22 '--' eg. a-- is a postfix decrement operator.
00:27 --a is a prefix decrement operator.
00:31 We will also learn about Typecasting.
00:35 To record this tutorial, I am using: Ubuntu 11.10 as the operating system,
00:40 gcc and g++ Compiler version 4.6.1 in Ubuntu.
00:48 The ++ operator increases the existing value of the operand by one.
00:54 a++ and ++a are equivalent to a = a + 1.
01:00 The -- operator decreases the existing value of the operand by one.
01:06 a-- and --a are equivalent to a = a - 1.
01:13 I will now demonstrate the use of increment and decrement operators with the help of a C program.
01:19 I have already made the program, so I'll explain the code.
01:25 Here, we have the code for increment and decrement operators in C.
01:30 Here, I have taken an integer variable a that holds the value 1.
01:35 This way we will be able to observe the changes in the value of a.
01:39 It will thus give us a better idea about the working of the operators.
01:47 Let's see how the postfix increment operator works.
01:51 The output of this printf statement is 1.
01:55 The value won't change.
01:57 This is because the postfix operation occurs after the operand is evaluated.
02:04 If an operation is performed on a++, it is performed on the current value of a.
02:10 After that the value of a is incremented.
02:17 Now if we see the value of a here, it has been incremented by 1.
02:27 We again initialize 'a' to 1 so as to reflect on the changes.
02:35 We now come to the prefix increment operators.
02:38 This printf statement prints 2 on the screen.
02:42 This is because a prefix operation occurs before the operand is evaluated.
02:49 So the value of 'a' is first incremented by 1 and then it is printed.
02:58 We again print a's value to see that there are no further changes.
03:03 Now let's check by executing this code.
03:07 I will comment out the following lines. Type /*, */
03:19 Click on Save.
03:22 I have saved my file as incrdecr.c.
03:29 Open the terminal window by pressing Ctrl, Alt and T keys simultaneously.
03:35 To compile, type the following on the terminal; gcc space incrdecr dot c space minus o space incr. Press Enter.
03:51 To execute the code, type ./incr (dot slash incr). Press enter.
03:59 The output is displayed on the screen.
04:01 This is the output when you print a++.
04:06 This is the output when you print ++a.
04:09 We can see that the result is as discussed before.
04:13 Now Coming back to the rest of the program.
04:16 I will now explain the postfix and prefix decrement operators.
04:21 Remove the multi-line comments from here and here .
04:29 We now again assign the value of 1 to a.
04:35 This printf statement outputs the value of 1 as explained previously.
04:40 a's value will be decremented after a-- is evaluated as it is a postfix expression.
04:47 The next statement prints a's value as o.
04:51 a's value has now being decremented by 1.
04:54 We now have the prefix decrement operator.
04:58 Output of this printf statement would be 0.
05:00 As it is a prefix operation.
05:05 The prefix operation occurs before the operand is evaluated.
05:09 This printf statements output is 0.
05:11 No further changes have been made to a's value.
05:15 Type return 0; and close the ending curly bracket.
05:21 Click on Save.
05:24 Switch back to the terminal.
05:27 To compile, type the following on the terminal; gcc space incrdecr dot c space minus o space incr. Press Enter.
05:42 To execute, type ./incr. Press Enter.
05:52 This is the output when you print a--.
05:56 This is the output when you print --a.
05:59 So, now we see how the increment and decrement operator work.
06:05 If we want to write the same program in C++,
06:07 I can make a few changes to the above C code.
06:10 Let me go back to the editor.
06:13 Here is the C++ file with the necessary code.
06:16 Notice that the header is different from the C file header.
06:20 We have the using namespace statement also.
06:24 Also note that the output statement in C++ is cout.
06:28 So, apart from these differences, the two codes are very similar.
06:33 Save the file. The file is saved with an extension .cpp.
06:40 Let's compile the code.
06:42 Open the terminal and type g++ space incrdecr dot cpp space minus o space incr. Press Enter.
07:00 To execute, type ./ incr (dot slash incr). Press Enter.
07:07 The output is displayed on the screen.
07:10 So, we see the output is identical to the C program.
07:15 We now have the concept of typecasting.
07:17 It is implemented the same way in both C and C++.
07:22 Typecasting is used to make a variable of one type, act like another type.
07:27 Typecasting is done by enclosing the data type, you want, within parentheses.
07:33 This cast is put in front of the variable you want to cast.
07:38 This typecast is valid for one single operation only.
07:42 Now a' will behave as a float variable, for a single operation.
07:47 Here is an example that I have already created.
07:50 I shall now explain the code.
07:54 We first declare variables a and b as integers and c as float.
08:00 a is assigned the value of 5. b is assigned the value of 2.
08:06 We will perform operations on a and b.
08:10 We divide a by b. The result of division is stored in c.
08:14 We have used %.2f to denote a precision of 2 decimal places.
08:20 The result displayed will be 2.00 against the expected result of 2.50.
08:25 The fractional part has been truncated as both the operands a and b are integers.
08:31 To perform real division, one of the operands will have to be typecast to float.
08:35 Here we are typecasting a to float. c now holds the value of real division.
08:41 Now the result of real division is displayed. The answer is 2.50 as expected.
08:47 Type return 0; and close the ending curly bracket.
08:51 Click on Save. Save the file with .c (dot c) extension.
08:55 I have saved my file as typecast.c.
08:59 Open the terminal.
09:01 To compile, type gcc space typecast dot c space minus o space type. Press Enter.
09:17 To execute, type ./type. Press Enter.
09:25 The output is displayed on the screen.
09:27 Looking at the two values we see the effects of typecasting.
09:32 We will summarize the tutorial now.
09:34 In this tutorial we learnt-
09:36 how to use the increment and decrement operators,
09:40 we learnt about the forms, Postfix and Prefix,
09:44 also we learnt about typecasting and how it is used.
09:47 As an assignment:
09:49 Write a program to solve the following expression, a divided by b plus c divided by d.
09:56 The values of a, b, c and d are taken as input from the user.
10:01 Use typecasting to perform real division.
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10:55 This is Ritwik Joshi from IIT Bombay.Thank you for joining.
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