C-and-C++/C3/Strings/English-timed
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Revision as of 20:32, 15 February 2015 by Sandhya.np14 (Talk | contribs)
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 an 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. |