C-and-C-Plus-Plus/C2/Scope-of-Variables-in-C-and-C-Plus-Plus/English

Title of script: Scope of variables

Author: Ashwini R. Patil

Keywords: Scope of variables, global variable, local variable, Video tutorial

Visual Cue	Narration
Slide 1	Welcome to the spoken tutorial on Scope of variables in C and C++.
Slide 2	In this tutorial we will learn, Scope of variable. Global variable. Local variable. We will do this with the help of example. We will also see some common errors and their solutions.
Slide 3	To record this tutorial, I am using Ubuntu Operating System version 11.04, gcc and g++ Compiler version 4.6.1 on Ubuntu
Slide 4	Let us start with the introduction to the scope of variables. It is the region of code within which the variable can be accessed. Depending on its type and place of declaration it is divided into two catagories: Global Variable. Local Variable.
Type: #include<stdio.h>	Let us see an example, I have already typed the code on the editor, So i will open it
Point the cursor scope.c	I have saved the file with the name scope.c. Let me explain the code now.
Highlight #include <stdio.h>	This is our header file.
Highlight int a=5; int b=2;	Here we have declared two global variables a and b. And we have initialized them by assigning value of 3 and 5. A global variable is available to all functions in your program. These are declared outside any functions above main() funtion. These have a Global scope.
Highlight void add()	Here we have declared a function add without arguments.
Highlight int c; c = a+b;	Then we have declared a local variable c. The sum of a and b will be stored in c. A local variable is available only to the function inside which it is declared. These variables are declared inside a block. These have local scope.
Highlight printf("Sum is %d\n",c);	Then we print the sum.
Highlight int main()	This is our main function.
Highlight add();	The add function is called and then executed.
Highlight return 0;	This is our return statement.
Click on save	Now Click on save.
	Let us execute the program.
Open the terminal Ctrl, Alt and T keys simultaneously	Please open the terminal by pressing Ctrl, Alt and T keys simultaneously
Type gcc scope.c -o sco To execute Type ./sco	To compile the program type, gcc scope.c -o sco To execute Type ./sco
Highlight Output	Here the output is displayed as Sum of a and b is 8
Click on save	Click on save. Let us execute.
On the terminal	Come back to our terminal. Now compile and execute as earlier.
Highlight Output	Here the output is displayed as Sum of a and b is 7
On the editor	NOW LET US SEE HOW TO EXECUTE THE SAME PROGRAM IN C++ Come back to our program
Go to File menu Click on Save as option Type .cpp	Now click on File menu. click on Save as option. Save the file with .cpp extension.
	Now let me change a few things here
Delete <stdio.h> Type <iostream>	First we will change the header file as iostream.
Type using namespace std;	We will include the using statement here.
	The function declaration in C++ is same as in C, So no need to change anything here.
Type cout <<	Now replace the printf statement with cout statement As we use cout<< function to print a line in C++.
Delete %d\n	We don't need the format specifier and '\n' here, So delete it.
Type <<	Now type two opening angle brackets here Then type sum two opening angle brackets again, and within the double quotes backslash n. Delete the closing bracket.
On the terminal	Let us compile. Come back to the terminal.
Type g++ scope.cpp -o sco1 Type ./sco1	Type, g++ scope.cpp -o sco1, and press Enter. To execute, Type, ./sco1
Highlight output	Here the output is displayed as, Sum of a and b is 9.
Errors Type int a = 2;	Now we will see some common errors which we can come across. Suppose here I will declare variable a again, Type int a = 2;
On the terminal	Click on save. Come back to the terminal.
Highlight Error	Let us compile, We see an error that declaration of int a shadows a parameter. a is a global variable. It has a global scope. We cannot declare the variable twice as it is already declared globally We can only declare variable a as a local variable now.
On the editor	Come back to the program. Let us fix the error.
Delete int a = 2;	Remove this declaration.
Click on save	Click on save.
On the terminal	Let us execute. Come back to our terminal.
	Let us compile and execute as before.
	Yes it is working. Now come back to our slides.
Slide 7	As an assignment, Write a program to print the difference of two numbers.
Slide 8 About the Spoken Tutorial Project	Watch the video available at the link shown . It summarises the Spoken Tutorial project. If you do not have good bandwidth, you can download and watch it.
Slide 9 Spoken Tutorial Workshops	The Spoken Tutorial Project Team, Conducts workshops using spoken tutorials . Gives certificates to those who pass an online test . For more details, please write to, contact@spoken-tutorial.org
Slide Number 10 Acknowledgement	Spoken Tutorial Project is a part of the Talk to a Teacher project. It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this Mission is available at: http://spoken-tutorial.org\NMEICT-Intro.
	This is Ashwini Patil from IIT Bombay signing off Thank You for joining.

Contributors and Content Editors

Ashwini, Chandrika