Difference between revisions of "C-and-C++/C3/Strings/English-timed"
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Revision as of 17:26, 8 February 2015
| Time | Narration |
| 00:01 | Welcome to the spoken-tutorial on Strings in C and C++. |
| 00:06 | In this tutorial we will learn: |
| 00:08 | *What is a string. |
| 00:10 | *Declaration of a string. |
| 00:13 | *Initialization of a string. |
| 00:15 | *Few examples on string. |
| 00:17 | We will also see some common errors and their solutions. |
| 00:22 | To record this tutorial, I am using |
| 00:25 | Ubuntu Operating System version 11.04, |
| 00:29 | gcc and g++ Compiler version 4.6.1 . |
| 00:35 | Let us start with the introduction to strings. |
| 00:38 | String is a sequence of characters that is treated as a single data item. |
| 00:44 | Size of string = length of string + 1. |
| 00:49 | Let me tell you how to declare a string. |
| 00:52 | The syntax for this is |
| 00:55 | char name of string and size. |
| 00:59 | char is the data type, name of the string is the string name, and we can give the size here. |
| 01:06 | Eg: here we have declared a character string names with size 10. |
| 01:13 | Now we will see an example. |
| 01:15 | I have already typed the program, I will open it. |
| 01:19 | Note that our file name is string.c |
| 01:23 | In this program, we will take a string as an input from the user and print it. |
| 01:29 | Let me explain the code now. |
| 01:32 | These are our header files. |
| 01:34 | Here string.h includes the declarations, functions, constants of string handling utilities. |
| 01:43 | Whenever we work on string functions, we should include this header file. |
| 01:47 | This is our main() function. |
| 01:49 | Here we are declaring the string strname with size 30. |
| 01:55 | Here we are accepting a string from the user. |
| 01:58 | To read a string, we can use scanf() function with format specifier %s. |
| 02:05 | We are using the caret sign and \n to include the spaces with the string. |
| 02:11 | Then we print the string. |
| 02:13 | And this is our return statement. |
| 02:16 | Now click on Save. |
| 02:18 | Let us execute the program. |
| 02:20 | Please open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard. |
| 02:30 | To compile, type gcc space string.c space -o space str |
| 02:37 | And press Enter . |
| 02:40 | To execute, type ./str (dot slash str). |
| 02:43 | now press Enter. |
| 02:46 | Here it is displayed as Enter the string . |
| 02:49 | I will type Talk To A Teacher. |
| 02:56 | Now press Enter. |
| 02:58 | The output is displayed as The string is Talk To A Teacher. |
| 03:03 | Now let us switch back to our slides. |
| 03:06 | Until now we discussed about the declaration of a string. |
| 03:10 | Now we are going to discuss how to initialize the string. |
| 03:13 | The syntax for this is |
| 03:16 | char var_name[size] = “string”; |
| 03:20 | Eg: Here we have declared a character string “names”"' with size 10 and the string is “Priya”"' |
| 03:28 | Another syntax is |
| 03:31 | char var_name[ ] = {'S', 't', 'r', 'i', 'n', 'g'} within single quotes |
| 03:36 | eg: char names[10] = {'P', 'r', 'i', 'y', 'a'} in single quotes |
| 03:42 | Let me show you how to use the first syntax with an example. |
| 03:48 | Switch back to our Editor. We will use the same example. |
| 03:52 | First, press shift, ctrl and s keys simultaneously on your keyboard. |
| 03:58 | Now save the file with the name stringinitialize. |
| 04:03 | Now click on Save. |
| 04:06 | We are going to initialize the string. |
| 04:08 | Hence, at the 5th line, type |
| 04:11 | = and within the double quotes “Spoken-Tutorial”; |
| 04:20 | Now, click on Save . |
| 04:22 | Now remove these two lines, as we are only going to print the string. |
| 04:27 | Click on Save. |
| 04:30 | Let us execute. |
| 04:31 | Come back to our terminal. |
| 04:33 | To compile, type |
| 04:35 | gcc space stringinitialize.c space -o space str2 |
| 04:44 | Here we have str2 because we don't want to overwrite the output parameter str for the file string.c. |
| 04:54 | Now press Enter. |
| 04:56 | To execute, type ./str2 |
| 05:00 | The output is displayed as "The string is Spoken-Tutorial". |
| 05:06 | Now we will see some common errors which we can come across . |
| 05:09 | Come back to our program. |
| 05:11 | Suppose, here we type the spelling of string as sting. |
| 05:16 | Now click on Save. |
| 05:18 | Let us execute. |
| 05:19 | Come back to our terminal. |
| 05:21 | Now compile as before. |
| 05:23 | We see a fatal error. |
| 05:25 | sting.h: no such file or directory |
| 05:28 | compilation terminated |
| 05:30 | Come back to our program. |
| 05:32 | This is because the compiler is not able to find the header file with the name sting.h . |
| 05:39 | Hence it is giving an error. |
| 05:41 | Let us fix the error. |
| 05:43 | Type r here. |
| 05:45 | Now click on Save. |
| 05:46 | Let us execute again. |
| 05:47 | Come back to our terminal. |
| 05:50 | Compile as before, execute as before. |
| 05:54 | Yes, it is working! |
| 05:56 | Now, let us see another common error. |
| 05:59 | Come back to our program. |
| 06:02 | Suppose, here I will type int in place of char. |
| 06:06 | Now, click on Save . |
| 06:07 | Let us see what happens. |
| 06:09 | Come back to our terminal. |
| 06:11 | Let me clear the prompt. |
| 06:15 | Compile as before. |
| 06:17 | We see an error. |
| 06:19 | Wide character array initialized from non-wide string . |
| 06:24 | format %s expects argument of type 'char' but argument 2 has type 'int'. |
| 06:32 | Come back to our program. |
| 06:36 | This is because we used %s as the format specifier for string. |
| 06:42 | And we are initializing it with an integer data type. |
| 06:47 | Let us fix the error. |
| 06:49 | Type char here. |
| 06:51 | Click on Save. |
| 06:53 | Let us execute. Come back to our terminal. |
| 06:56 | Compile as before, execute as before. |
| 07:00 | Yes, it is working! |
| 07:03 | Now we will see how to execute the same program in C++. |
| 07:08 | Come back to our program. |
| 07:11 | Let me open our file string.c. |
| 07:15 | We will edit the code here. |
| 07:18 | First, press shift, ctrl and S keys simultaneously on your keyboard. |
| 07:25 | Now save the file with an extension .cpp(dot cpp). |
| 07:29 | and click on Save. |
| 07:33 | Now we will change the header file as iostream. |
| 07:38 | Include the using statement. |
| 07:43 | Now click on Save. |
| 07:47 | Now we will delete this declaration. |
| 07:50 | And will declare a string variable. |
| 07:53 | Type string space strname and a semicolon. |
| 07:59 | Click on Save. |
| 08:02 | Replace the printf statement with the cout statement. |
| 08:07 | Delete the closing bracket here. |
| 08:11 | Delete the scanf statement and type getline opening bracket closing bracket within the brackets type(cin, strname) . |
| 08:24 | At the end, type a semicolon. |
| 08:28 | Now again, replace the printf statement with the cout statement. |
| 08:36 | Delete the format specifier and \n . |
| 08:40 | Now delete the comma |
| 08:42 | Type two opening angle brackets, delete the bracket here. |
| 08:49 | Type two opening angle brackets and within the double quotes type \n . |
| 08:54 | And click on Save. |
| 08:58 | Here we have declared a string variable 'strname' |
| 09:03 | Since we do not use the format specifier in C++, the compiler should know that 'strname' is a string variable. |
| 09:13 | Here we use getline to extract the characters from the input sequence. |
| 09:18 | It stores them as a string. |
| 09:22 | Now let us execute the program. Come back to our terminal. |
| 09:27 | Let me clear the prompt. |
| 09:30 | To compile, type |
| 09:32 | g++ space string.cpp space -o space str3 |
| 09:39 | and press Enter. |
| 09:41 | To execute, type ./str3 (dot slash str3). |
| 09:46 | Press Enter. |
| 09:47 | It is displayed as Enter the string. |
| 09:50 | I will enter as Talk To A Teacher . |
| 09:55 | Now press Enter. |
| 09:57 | The output is displayed as |
| 09:59 | "The string is Talk To A Teacher" |
| 10:03 | We can see that the output is similar to our C code. |
| 10:07 | Now come back to our slides. |
| 10:10 | Let us summarize. |
| 10:11 | In this tutorial we learnt: |
| 10:13 | *Strings |
| 10:14 | *Declaration of a string |
| 10:16 | eg: char strname[30] |
| 10:20 | *Initialization of a string |
| 10:21 | eg: char strname[30] = “Talk To A Teacher” |
| 10:26 | As an assignment, |
| 10:28 | write a program to print a string using the 2nd syntax. |
| 10:34 | Watch the video available at the link shown below. |
| 10:37 | It summarizes the Spoken Tutorial project. |
| 10:40 | If you do not have good bandwidth, you can download and watch it. |
| 10:44 | The Spoken Tutorial Project Team: |
| 10:46 | Conducts workshops using spoken tutorials. |
| 10:49 | Gives certificates to those who pass an online test. |
| 10:54 | For more details, please write to, contact@spoken-tutorial.org. |
| 11:01 | Spoken Tutorial Project is a part of Talk to a Teacher project. |
| 11:04 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 11:12 | More information on this Mission is available at the link shown below. |
| 11:16 | This is Ashwini Patil from IIT Bombay, signing off. |
| 11:20 | Thank You for watching. |
