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

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 Type casting.
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 lets 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. 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 multiline 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 its a postfix expression.
04:47	The next statement prints a's value as o.
04:51	A's value has now being decremeted 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 being 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 works.
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.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 a 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 parenthesis.
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 integer 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 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 learn't 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.

Contributors and Content Editors

Ashwini, Devisenan, Jyotisolanki, Krupali, PoojaMoolya, Pratik kamble, Sandhya.np14