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Time Narration
00:01 Welcome to the spoken tutorial on First C program.
00:05 In this tutorial, we will learn
00:08 How to write a simple C program
00:11 How to compile it
00:13 How to execute it We will also explain some common errors and their solutions.
00:18 To record this tutorial, I am using
00:21 Ubuntu operating system version 11.10 and gcc Compiler version 4.6.1 on Ubuntu.
00:31 To practice this tutorial,
00:33 You should be familiar with Ubuntu Operating System and an Editor.
00:38 Some editors are vim and gedit.
00:42 I will use 'gedit' in this tutorial.
00:45 For relevant tutorials please visit our website which is as shown. http://spoken-tutorial.org
00:51 Let me tell you how to write a C program through an example.
00:55 Open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard.
01:07 Now let's open the text editor. So, at the prompt, type
01:12 “gedit” space “talk” dot “c” space “&” sign.
01:20 We use ampersand (&) to free up the prompt.
01:24 Please note that all the C files will have extension “.c”(dot C).
01:30 Now Press Enter,
01:32 the text editor has opened.
01:36 Let us start to write a program.
01:39 Type double slash “//” space
01:42 “My first C program”.
01:48 Here, double slash is used to comment the line.
01:52 Comments are used to understand the flow of program.
01:56 It is useful for documentation.
01:58 It gives us information about the program.
02:01 The double slash is called as single line comment.
02:07 Now press Enter.
02:09 Type (hash) “#include” space opening bracket , closing bracket.
02:17 It is always a good practice to complete the brackets first, and then start writing inside it.
02:24 Now Inside the bracket, type“stdio” “(dot).” “h” .
02:30 stdio.h is a header file.
02:33 A program must contain this header file when it uses standard input/output functions.
02:41 Now press Enter.
02:43 type “int” space “main” opening bracket, closing bracket.
02:50 main is a special function.
02:52 It denotes that the execution of the program begins from this line.
02:58 The opening bracket and closing bracket is called as parenthesis.
03:04 Parenthesis followed by main is to tell the user that main is a function.
03:11 Here the int main function takes no arguments.
03:15 It returns a value of type integer.
03:18 We will learn about data types in another tutorial.
03:23 Now Let us switch to the slides to know more about main function. Let us go to the next slide.
03:29 Every program should have one main() function.
03:33 There should NOT be more than one main function.
03:36 Otherwise the compiler cannot locate the beginning of the program.
03:41 The empty pair of parentheses indicates that main has no arguments.
03:46 The concept of arguments will be discussed in detail in the upcoming tutorials.
03:52 Now let us come back to our program.
03:55 Press Enter.
03:58 Type opening curly bracket “{”.
04:00 The opening curly bracket marks the beginning of the function main.
04:04 Then Type closing curly bracket “}”.
04:08 The closing curly bracket indicates the end of the function main.
04:13 Now Inside the bracket press Enter twice,
04:16 move the cursor one line up.
04:20 Indentation makes the code easier to read.
04:23 It also helps to locate errors faster.
04:25 So let us give three space here
04:29 And Type “printf” opening bracket closing bracket “()” .
04:34 printf is a standard C function to print the output on the terminal.
04:39 Here, inside the brackets, within the double quotes.
04:43 Anything within the double quotes, in the printf statement, will be printed on the terminal.
04:50 Type“Talk To a Teacher backslash n”.
04:59 Backslash n “\n” signifies newline.
05:03 As a result, after execution of the printf function, the cursor moves to the new line.
05:10 Every C statement must end with a semicolon “;”.
05:15 Hence, type it at the end of this line.
05:19 Semicolon acts as a statement terminator.
05:24 Now press Enter give three space here.
05:27 And type “return” space “0” and a semicolon.
05:34 This statement returns the integer zero.
05:38 An integer has to be returned for this function because the function type is int.
05:45 The return statement marks the end of executable statements.
05:51 We will learn more about the returned values in another tutorial.
05:55 Now click on"Save" button to save the file.
06:00 It is a good habit to save files frequently.
06:03 This will protect you from sudden power failures.
06:05 It will also be useful in case the applications were to crash.
06:10 Let us now compile the program, come back to a terminal.
06:15 Type “gcc” space “talk.c” space hyphen “-o” space “myoutput”,
06:24 gcc is the compiler,
06:27 talk.c is our filename .
06:30 -o myoutput says that the executable should go to the file myoutput.
06:37 Now Press Enter.
06:39 We see that the program is compiled.
06:42 By typing ls space (hypen) -lrt, we can see that myoutput is the last file to be created.
06:54 To execute the program, type (dot slash)“./myoutput” , press Enter.
07:01 Here the output is displayed as “Talk To a Teacher”.
07:06 As I said before, return is the last statement to be executed.
07:10 Thus, after the return statement nothing will be executed. Let us try it out.
07:15 come back to our program.
07:17 After the return statement, let us include one more printf statement,
07:22 give space here, type printf opening bracket, closing bracket.
07:27 Inside the bracket within the double quotes type Welcome backslash n , at the end type a semicolon.
07:35 Now click on save.
07:37 Let us compile and execute come back to our terminal.
07:41 you can recall the previously entered commands by using up arrowkey.
07:46 That is what I did now.
07:51 We see that the second statement welcome is not executed.
07:58 Now come back to our program.
08:00 Let us write the 'Welcome' statement above the return statement.
08:06 Click on Save.
08:09 Let us compile and execute.
08:15 We see that the second printf statement welcome has also been executed.
08:23 Now let us see the common errors which we can come across. Come back to our program.
08:29 Suppose here I will miss the dot in “stdio.h”, click on Save.
08:36 Let us compile and execute .
08:41 We see that there is a fatal error at line no.2 in our talk.c file.
08:48 The compiler cannot find a header file with the name “stdioh”. Hence it is giving an error "no such file or directory".
08:59 And the compilation is terminated.
09:03 Let us now fix the error come back to a program. Reinsert the dot “.”, click on Save.
09:11 Let us compile and execute. Yes, it is working.
09:19 I will show you another common error.
09:22 Let us switch back to the program.
09:25 Now, suppose here I will miss the semicolon at the end of the line.
09:31 Click on Save. Let us compile and execute.
09:41 We see that there is an error at line no.6 in our talk.c file. that "expected ';' (semicolon) before 'printf'".
09:51 Come back to our program.
09:54 As I said before, semicolon acts as a statement terminator.
09:58 So it will search for it at the end of the line.5 and at the beginning of the line.6.
10:06 This is line 6.
10:09 This is the last place where you can put the semicolon.
10:12 Recall that the compiler also gives the error message on line 6.
10:18 Let us try what happens if we put the semicolon here.
10:23 Click on Save .
10:26 Let us Compile and execute.
10:30 Yes, it is working.
10:32 Now come back to our program. Let us type the semicolon here at the end of this line
10:40 as it is a conventional practice to type the semicolon at the end of the line.
10:46 Now click on Save.
10:49 Let us Compile and execute. Yes it is working.
10:54 Now let us go back to our slides.
10:57 As an Assignment
10:59 Write a program to print "Welcome to the World of C"
11:02 See what happens if “\n” is not included in the printf statement.
11:08 This brings us to the end of this tutorial.
11:12 Watch the video available at the link shown below,
11:15 It summarises the Spoken Tutorial project.
11:18 If you do not have good bandwidth, you can download and watch it.
11:22 The Spoken Tutorial Project Team
11:24 Conducts workshops using spoken tutorials.
11:28 Gives certificates to those who pass an online test.
11:31 For more details, please write to contact [at] spoken hyphen tutorial dot org
11:38 Spoken Tutorial Project is a part of the Talk to a Teacher project.
11:42 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
11:47 More information on this Mission is available at the link shown below:
11:51 This is Ashwini Patil from IIT Bombay signing off. Thank you for watching.