Difference between revisions of "C-and-Cpp/C2/First-Cpp-Program/English-USA"
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Latest revision as of 14:52, 10 April 2015
| Time | Narration |
| 00:02 | Welcome to the spoken tutorial on First C++ program. |
| 00:07 | In this tutorial I am going to explain, |
| 00:10 | *How to write a C++ program |
| 00:13 | *How to compile it |
| 00:14 | *How to execute it |
| 00:17 | We will also explain some common errors and their solution. |
| 00:22 | To record this tutorial, I am using Ubuntu operating system version 11.10 and |
| 00:29 | G++ Compiler version 4.5.2 on Ubuntu. |
| 00:35 | To practice this tutorial, |
| 00:37 | You should be familiar with Ubuntu Operating System and an Editor |
| 00:44 | Some editors are 'vim' and 'gedit'. |
| 00:48 | I am using 'gedit' in this tutorial. |
| 00:50 | For relevant tutorial please visit our website which is as shown. |
| 00:56 | Let me tell you how to write a C++ program through an example. |
| 01:01 | Open the terminal Window using Ctrl, Alt and T keys simultaneously on your keyboard. |
| 01:09 | To open the text editor, type on the terminal. |
| 01:13 | “gedit” space “talk” dot “.cpp” space ampersand “&” sign. |
| 01:21 | We use the “&” to free up the prompt. |
| 01:25 | Please note that all the C++ files will have the extension “.cpp”. |
| 01:31 | Now Press Enter, |
| 01:33 | the text editor has opened. |
| 01:35 | Let us start to write a program. |
| 01:38 | Type double slash “//” space “My first C++ program”. |
| 01:44 | Here, double slash is used to comment the line. |
| 01:49 | Comments are used to understand the flow of program. |
| 01:52 | It is useful for documentation. |
| 01:55 | It gives us information about the program. |
| 01:59 | The double slash is called as single line comment. Now press Enter. |
| 02:05 | Type (hash) “#include”, space, opening angle bracket, closing angle bracket . |
| 02:13 | It is a good practice to complete the brackets first, and then start writing inside it. |
| 02:20 | Now Inside the bracket, type “iostream” . |
| 02:23 | Here iostream is a header file. |
| 02:26 | This file includes the declaration of standard input output functions in C++. Now press Enter. |
| 02:35 | Type “using” space “namespace” space “std” and a semicolon “;” . |
| 02:45 | The using statement informs the compiler that you want to use the std namespace. |
| 02:52 | The purpose of namespace is to avoid name collisions. |
| 02:56 | It is done by localizing the names of identifiers. |
| 03:00 | It creates a declarative region and defines a scope. |
| 03:05 | Anything defined within a namespace is in the SCOPE of that namespace. |
| 03:11 | Here std is the namespace in which entire standard C++ library is declared. Now press Enter. |
| 03:20 | Type “int” space “main” opening bracket, closing bracket . |
| 03:26 | main is a special function. |
| 03:30 | It denotes that the execution of the program begins from this line. |
| 03:34 | The opening and the closing bracket is called as Parenthesis. |
| 03:39 | Parenthesis followed by main tells the user that main is a function. |
| 03:45 | Here, the int main() function takes no arguments and returns a value of type integer. |
| 03:52 | We will learn about data types in another tutorial. |
| 03:56 | Now let us switch to the slides to know more about main function. |
| 04:02 | Every program should have one main function. |
| 04:04 | There should NOT be more than one “main” function. |
| 04:09 | Otherwise the compiler cannot locate the beginning of the program. |
| 04:13 | The empty pair of parentheses indicates that main has no arguments. |
| 04:19 | The concept of arguments will be discussed in the upcoming tutorials. |
| 04:24 | Now come back to our program. Press Enter. |
| 04:29 | Type opening curly bracket “{”. |
| 04:32 | The opening curly bracket marks the beginning of the function main(). |
| 04:37 | Then Type closing curly bracket “}”. |
| 04:40 | The closing bracket indicates the end of the function main(). |
| 04:45 | Now, inside the bracket press enter twice. |
| 04:49 | Move the cursor one line up. |
| 04:51 | Indentation makes the code easier to read. |
| 04:54 | It also helps to locate errors faster. |
| 04:58 | So let us give a space here. |
| 05:01 | And type “cout” space two opening angle bracket '. |
| 05:07 | Here cout is a standard C++ function to print the output on the terminal. |
| 05:14 | Now after the brackets, type within double quotes. |
| 05:18 | Anything within the double quotes, in the cout functions, will be printed. |
| 05:24 | Now inside a quote type“Talk to a teacher backslash n” (\n). |
| 05:31 | Here \n signifies newline. |
| 05:35 | As a result, after execution of the cout function, the cursor moves to the new line. |
| 05:41 | Every C++ statement must end with a semicolon. |
| 05:45 | Hence type it at the end of this line. |
| 05:48 | Semicolon acts as a statement terminator. Now press Enter. |
| 05:53 | Give a space here and Type “return” space “0” and a semicolon “;”. |
| 06:00 | This statement returns the integer zero. |
| 06:03 | An integer has to be returned for this function because the function type is int. |
| 06:10 | The return statement marks the end of executable statements. |
| 06:14 | We will learn more about the returned values in another tutorial. |
| 06:20 | Now click on “Save” button to save the file. |
| 06:23 | It is a good habit to save files frequently. |
| 06:26 | This will protect you from sudden power failures. |
| 06:30 | It will also be useful in case the applications were to crash. |
| 06:34 | Let us now compile the program. |
| 06:36 | Come back to our terminal. |
| 06:39 | Type “g++” space “talk.cpp” space hyphen “-o” space “output”. |
| 06:49 | Here g++ is the compiler used to compile C++ programs. |
| 06:55 | talk.cpp is our filename. |
| 06:59 | hyphen -o output says that the executable should go to the file "output". |
| 07:05 | Now press Enter. |
| 07:07 | We see that the program is compiled. |
| 07:10 | By typing ls space hyphen lrt, we can see that output is the last file to be created. |
| 07:19 | Let us execute a program, type “./output” (dot slash output). |
| 07:24 | And Press Enter. |
| 07:27 | Here the output is displayed as “Talk to a teacher”. |
| 07:30 | Now let us see the common errors which we can come across. |
| 07:35 | Switch back to our text editor. |
| 07:38 | Suppose here we miss the }(closing curly bracket) |
| 07:42 | now save the file. |
| 07:44 | Let us execute. Come back to our terminal. |
| 07:48 | Now compile and run the program using the command we used before. We see an error. |
| 07:55 | We see that there is an error at line no.7 in our talk.cpp file that "expected curly bracket at the end of input". |
| 08:07 | Now Come back to our text editor . |
| 08:09 | As I said before, the closing curly bracket marks the end of the function main |
| 08:14 | Hence re-insert the bracket here. Now Save the file. |
| 08:19 | Let us execute it again. |
| 08:21 | You can recall the previously entered commands by using up arrow key. |
| 08:26 | That is what I did now. |
| 08:30 | Yes, it is working. |
| 08:32 | I will show you another common error. |
| 08:35 | Let us switch back to our text editor. |
| 08:37 | Now, suppose here we missed std. |
| 08:41 | Let us save the file. |
| 08:44 | Come back to our terminal . |
| 08:46 | Let us compile . |
| 08:48 | We see that there is an error at line no.3 and line no.6 in our talk.cpp file. |
| 08:56 | That "expected identifier before 'semicolon' " and " 'cout' was not declared in this scope". |
| 09:05 | As cout is the standard C++ library function. |
| 09:09 | and the entire C++ library function is defined under std namespace . |
| 09:15 | Hence it is giving an error. |
| 09:18 | Let us now fix the error. |
| 09:19 | Come back to our Text editor. Type std here. |
| 09:23 | Let us save it. |
| 09:25 | Let us compile it again. |
| 09:29 | Yes, it is working. |
| 09:32 | As an assignment, |
| 09:33 | write a program to print your name and city. |
| 09:37 | We used single line comment in this tutorial. |
| 09:40 | Now just try to give a multiline comment. |
| 09:44 | Watch the video available at the link shown below. |
| 09:46 | It summarizes the Spoken Tutorial project. |
| 09:48 | If you do not have good bandwidth, you can download and watch it. |
| 09:53 | The Spoken Tutorial Project Team: |
| 09:55 | Conducts workshops using spoken tutorials. |
| 09:58 | Gives certificates to those who pass an online test. |
| 10:01 | For more details, please write to contact @spoken-tutorial.org |
| 10:10 | Spoken Tutorial Project is a part of the Talk to a Teacher project. |
| 10:14 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 10:20 | More information on this Mission is available at the link shown below. |
| 10:25 | This is Jean Bonnet from IIT Bombay signing off. |
| 10:28 | Thank you for watching. |
