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

Title of script: First C program

Author: Ashwini Patil

Keywords: C Program, stdio.h, printf(), int main(), Video Tutorial

Visual Cue	Narration
Slide 1	Welcome to the spoken tutorial on First C program.
Slide 2 Learning Objectives	In this tutorial you will learn To write a simple C program To compile it To execute it We will also explain some common errors and their solutions.
Slide 3 System Requirements	To record this tutorial, I am using Ubuntu operating system version 11.10 and gcc Compiler 4.6.1 on Ubuntu
Slide 4 Prerequisites	To practice this tutorial, You should be familiar with Ubuntu Operating System an Editor Some editors are vim and gedit I will use gedit in this tutorial For relevant tutorials please visit our website: http://spoken-tutorial.org
Open the terminal Open the terminal using Ctrl + Alt + T simultaneously	Let me tell you how to write a C program through an example Open the terminal by pressing Ctrl, Alt and T keys simultaneously
At the command prompt type: gedit talk.c &	Now let's open the text editor. So, at the prompt, type “gedit” space “talk” dot “c” space [ampersand] “&” We use ampersand (&) to free up the prompt
Highlight the .c extension	Please note that all the C files have the extension dot “c”
	Now Press Enter
	Now the text editor has opened
	Let us write a program
	Type double slash “//” space “My first C program”.
	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.
	Now press Enter
Type #include <>	Type hash “#include” space opening angle bracket “<”, closing angle bracket “>”
	It is always a good practice to complete the brackets first, and then start writing inside it
Type #include <stdio.h>	Inside the bracket, type “stdio” dot”.” “h”
Highlight stdio.h	stdio.h is a header file A program must contain this header file when it uses standard input/output functions.
Move cursor to the end of the line.	Move the cursor to the end of the line and press Enter .
Type int main()	Then type “int” space “main” opening bracket and closing bracket “()”.
Highlight main	Function main is a special function used by C It denotes that the execution of the program begins from this line The opening bracket and the closing bracket is called as parenthesis.
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 It returns a value of type integer.
	We will learn about data types in another tutorial.
Switch to the slides	Let us switch to the slides to know more about the main function.
Slide 5	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.
Switch to the editor	Now let us go back to our program.
Type {	Type the opening curly brace “{” The opening curly bracket marks the beginning of the function main.
Type }	Type the closing brace “}” The closing curly bracket indicates the end of the function main.
Press Enter twice within the braces Move the cursor one line up	Inside the braces press Enter twice, and then move the cursor one line up
Give a space	Indentation makes the code easier to read It also helps to locate errors faster So let us give three space here
Type printf()	Type “printf” and opening bracket and closing bracket “()” printf is a standard C function to print the output on the terminal
Highlight the text in the double quotes printf("Talk To a Teacher\n");	Here inside the brackets, type within double quotes, Anything within the double quotes in the printf statement will be pritned on the terminal. Type “Talk To a Teacher backslash n”
Highlight \n	Backslash n “\n” signifies newline As a result, after execution of the printf function, the cursor moves to a new line
Type semicolon (;)	Every C statement must end with a semicolon “;” Hence, type it at the end of this line. Semicolon acts as a statement terminator.
	Now press Enter give three space here
Type return 0;	Now type “return” space “0” and a semicolon “;”
	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.
Click on 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.
Type gcc talk.c -o myoutput	Let us now compile the program Please open the terminal Type “gcc” space “talk.c” space hyphen “-o” space “myoutput”
Highlight or point to each component of the statement	gcc is the compiler talk.c is the filename on compilation gcc creates an executable -o myoutput says that the executable should go to the file myoutput Press Enter.
Type ls -lrt	We see that the program is compiled By typing ls -lrt, we can see that myoutput is the last file to be created
Type ./myoutput	To execute the program, type dot slash “./myoutput” and press Enter.
	Here the output is displayed as “Talk To a Teacher”.
Type return 0;	As I said before, return is the last statement to be executed Thus after the return statement nothing will be executed Let us try it out.
Switch to the editor	Let us come back to our program.
Type printf("Welcome \n");	After the return statement, let us include one more printf statement type printf("Welcome \n");
Click on Save icon.	Now save it.
Type gcc talk.c -o myoutput Type ./myoutput	Let us compile and run the program as before gcc talk.c -o myoutput ./myoutput.
	We see that the second statement 'Welcome' is not executed.
Press up arrow key	On the terminal, you can recall the previously entered commands by using up arrow That is what I did now We see that the statements after return are not executed
Shift printf("Welcome \n"); above return 0;	Now come back to our program Let us write the 'Welcome' statement above the return statement
Click on Save	Save it
On the terminal, use up arrow to get “gcc talk.c -o myoutput” and press Enter.	Let us compile and execute We see that the second printf statement also has been executed
Errors	Now let us see the common errors which we can come across Let's switch to the editor
Type <stdio.h>	Suppose we miss the dot “.” in <stdio.h> I will retain rest of the code as it is
Click on Save Switch to the terminal	save the program Let us go to the terminal
On the terminal, use up arrow to get “gcc talk.c -o myoutput” and press Enter.	Now compile the program using the command we used before We see that There is a fatal error in our talk.c file at line no.1 and column no.18 The compiler cannot find a header file with the name “stdioh” hence the compilation is terminated.
Reinsert the dot “.”	Let us fix the error we made on the header file Reinsert the dot “.”
Click on Save	Save it
On the terminal, use up arrow to get “gcc talk.c -o myoutput” and press Enter.	Let us now execute it It is working.
Switch back to gedit	I will show you another common error Let us switch back to the editor
Type: printf("Talk To a Teacher\n")	Now, suppose that we miss the semicolon at the end of printf() statement.
Click on Save	Save it Switch to the terminal.
Type clear and press Enter	I will clear the terminal by typing “clear” command.
On the terminal, use up arrow to get “gcc talk.c -o myoutput” and press Enter.	Now compile the program using command that we have used before. And press Enter.
Point to line no. 5 and column no. 1 on the screen	we see an error message at line no.5 and column no.1 in talk.c file.
	As i said before semicolon acts as a statement terminator So it will search for it at the end of the line and also at the beginning of the next line.
Bring the cursor to line 5	Now come back to our program This is line 5
Point to the location	This is the last place where you can put the semicolon Recall that the compiler also gives the error message on line 5.
Put the semicolon at the beginning of line 6	Let us try what happens if we put the semicolon in the next line.
Click on Save	Save it
On the terminal, use up arrow to get “gcc talk.c -o myoutput” and press Enter.	Compile it and execute it
Back to the editor Put semicolon back in original location	Let us now fix the error
Click on Save	Click on Save
On the terminal, use up arrow to get “gcc talk.c -o myoutput” and press Enter.	Now execute it It is working
Slide 7 Assignment	As an Assignment Write a program to print "Welcome to the World of C" See what happens if we do not write “\n” in the printf statement.
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, please write to contact [at] spoken hyphen tutorial dot org
lide 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
Remain on previous slide No slide for this part	This is Ashwini Patil from IIT Bombay. Thank you for joining.

Contributors and Content Editors

Ashwini, PoojaMoolya