C-and-C++/C2/First-C++-Program/English

Title of script: First C++ program

Author: Ashwini Patil

Keywords: iostream, namespace, int main(), cout, .cpp

Visual Cue	Narration
Slide 1	Welcome to the spoken tutorial on First C++ program.
Slide 2 Learning Objectives	In this tutorial I am going to explain, How to write a C++ program How to compile it How to execute it We will also explain some common errors and their solution.
Slide 3 System Requirements	To record this tutorial, I am using Ubuntu operating system version 11.10 and G++ Compiler version 4.5.2 on Ubuntu.
Slide 4 Prerequisites	To practice this tutorial, You should be familiar with Ubuntu Operating System and an Editor Example vim, gedit I am using gedit in this tutorial For relevant tutorial Please visit our website: http://spoken-tutorial.org
Open the Terminal Open the terminal using Ctrl + Alt + T	Let me tell you how to write a C++ program through an example Open terminal Window using Ctrl, Alt and T keys simultaneously on your keyboard.
gedit talk.cpp &	To open the text editor, type “gedit” space “talk” dot “.cpp” space ampersand “&”.
Highlight &	We use the “&” to free up the prompt.
Highlight .cpp	Please note that all the C++ files will have the extension “.cpp”
	Press Enter Now the text editor has opened.
	Let us start to write a program.
//My first C++ program	Type double slash “//” space “My first C++ program”.
Highlight //	Here, double slash is used to comment the line Comments are used to understand the flow of program It is useful for documentation It gives us information about the program The double slash is called as single line comment.
Type #include <>	Type hash “#include” space opening angle bracket “<” closing angle bracket “>” .
Type #include <iostream>	Inside the bracket, type “iostream” .
	move the cursor at the end of line Press Enter.
	It is always a good practice to complete the brackets first, and then start writing inside it Here iostream is a header file This file includes the declaration of basic standard input output library in C++.
Type using namespace std;	Type “using” space “namespace” space “std” and a semicolon “;” .
	Press Enter.
Highlight using Highlight namespace Highlight std	The using statement informs the compiler that you want to use the std namespace The purpose of namespace is to avoid name collisions It is done by localizing the names of identifiers It creates a declarative region and defines a scope Anything defined within a namespace is in the SCOPE of that namespace std is the namespace in which entire standard C++ library is declared.
Type int main()	Type “int” space “main” opening bracket “(” closing bracket “)” .
	press Enter.
Highlight main()	Function main is a special function It denotes that the execution of the program begins from this line.
Highlight ()	Parenthesis followed by main is to tell the user that main is a function.
Highlight int main()	Here the int main function takes no arguments and returns a value of type integer.
	We will learn about data types in another tutorial.
	Let us switch to the slides to know more about the main function.
	Every program will have only one main function There should NOT be more than one “main” function Otherwise the compiler cannot locate the beginning of the program The empty pair of parentheses indicates that main has no arguments The concept of arguments will be discussed in detail in the upcoming tutorials.
Type {	Type opening curly bracket “{” This bracket marks the beginning of the function main.
Type }	Type closing curly bracket “}” The closing bracket indicates the end of the function main Inside the bracket press enter twice Move the cursor one line up.
	Indentation makes the code easier to read It also helps to locate errors faster Thus give a single space here.
Type cout <<	type “cout” space two opening angle bracket “<<” space .
Highlight cout<<	Here cout is a standard C++ function to print the output And << is an output operator.
Type cout << “Talk to a teacher\n”	Here after the brackets, type within the double quotes “Talk to a teacher backslash \n”.
Highlight “”	Anything within the double quotes in the cout << statement will be printed.
Highlight \n	\n signifies newline As a result, after execution of the cout function, the cursor moves to the new line.
Type “;”	Every C++ statement must end with a semicolon Hence type it at the end of this line.
Highlight ;	Semicolon acts as a statement terminator.
Type return 0;	Type “return” space “0” and a semicolon “;”.
Highlight return 0; Highlight int	This statement returns the integer zero An integer has to be returned for this function Because the function type is int The return statement marks the end of executable statements We will learn more about the returned values in another tutorial.
Save	Now click on the “Save” button to save the file It is a good habit to save files frequently This will protect you from sudden power failures It will also be useful in case the applications were to crash.
Compile	Let us now compile the program.
Type g++ talk.cpp -o output	Please open the terminal Type “g++” space “talk.cpp” space hyphen “-o” space “output”.
Highlight g++ Highlight talk.cpp Highlight -o output	g++ is the compiler used to compile C++ programs talk.cpp is the filename on compilation g++ creates an executable -o output says that the executable should go to the file output.
	We see that the program is compiled.
Type ls -lrt	By typing ls -lrt, we can see that output is the last file to be created.
Type ./output	To execute the program, type dot slash “./output” Press Enter.
Highlight Talk to a teacher	Here the output is displayed as “Talk to a teacher”.
Errors	Now let us see the common errors which we can come across Please switch to the editor.
{	Suppose we miss the { I will retain rest of the code as it is.
	save the program.
	Let us execute it again Let us go to the terminal
	Now compile and run the program using the command we used before.
Highlight error Highlight Line no.7 Highlight talk.cpp Highlight {	we see that there is an error at line no.7 in our talk.cpp file Expected curly bracket at the end of input.
	Come back to out program.
	As i said before the closing curly bracket marks the end of the function main Hence reinsert the bracket .
	Save it.
	Let us execute it You can recall the previously entered commands by using up arrow That is what I did now Yes it is working.
Error 2	I will show you another common error Let us switch back to the editor.
	Now, suppose here we missed std.
	Save it.
Highlight error Highlight Line no.3 and 6 Highlight talk.cpp Highlight ; Highlight cout	Compile and run it as before We see that there are errors at line no 3 and 6 in our talk.cpp file expected identifier before semicolon and cout was not declared in this scope.
	As cout is the standard C++ library function and the entire C++ library function is defined under std namespace Hence it is giving an error.
	Let us fix the error Come back to our program type std.
	Save it.
	Let us execute it Yes it is working.
	As an assignment, Write a program to print your name and city We used single line comment in this tutorial Now just try to give multiline comment Hint: /*.................. .....................*/
Slide 8 About the Spoken Tutorial Project	Watch the video available at the link shown http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial It summarises the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it.
Slide Number 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, 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 watching

Contributors and Content Editors

Ashwini, PoojaMoolya