Difference between revisions of "C-and-C++/C3/Strings/English"

Learning Objectives

• What is a string.
• Declaration of a string.
• Initialization of a string.
• Few examples on string.

We will also see some common errors and their solutions.

System Requirements

• Ubuntu Operating System version 11.04
• gcc and g++ Compiler version 4.6.1

Introduction to strings

String is a sequence of characters, that is treated as a single data item.

Size of string = length of string + 1

Declaration of the String

Syntax:

char val[10];

The syntax for this is

char name_of_string[size];

char, name of string and size

char is the data type, name of the string is the string-name, and we can give the size here.

Eg: here we have declared a character string names with size 10

I have already typed the program, so I will open it.

Note that our file name is string.c

In this program, we will take a string as an input from the user and print it.

Let me explain the code now.

#include<string.h>

Here string.h includes the declarations, functions, constants of string handling utilities.

Whenever we work on string functions, we should include this header file.

char strname[30];

Here we are declaring the string strname' with size '30'.

printf("Enter the string\n");

scanf("%[^\n]s",strname);

We are using the caret sign and \n to include the spaces with the string.

printf("The string is %s\n", strname);

And this is our return statement.

On the terminal

Please open the terminal window by pressing Ctrl, Alt and T keys simultaneously on your keyboard.

gcc strdeclare.c str

>> press Enter

gcc space string.c space -o space str

And press Enter

./str

>> press Enter

./str

now press Enter

Talk To A Teacher >> press Enter

now press Enter.

Output

Initialization of the string

Syntax:

char strinitialize[30] = “star”;

(or)

char strinitialize[] = {'S', 't', 'r'};

Until now we discussed about the declaration of a string.

Now we are going to discuss how to initialize the string.

The syntax for this is

char var_name[size] = “string”;

Eg: Here we have declared a character string "names" with size 30 and the string is "Priya"

Another syntax is

char var_name[ ] = {'S', 't', 'r', 'i', 'n', 'g'}; within single quotes

eg: char names[10] = {'P', 'r', 'i', 'y', 'a'}; in single quotes

Switch back to our Editor. We will use the same example.

Type

strinitialize.c

Now save the file with the name strinitialize.c

char name[30] = "Talk To A Teacher";

Hence, on the 5th line, type

= and within double quotes “Spoken- Tutorial”;

Now, click on Save

printf("Enter the string\n");

scanf("%[^\n]s",strname);

Let us execute.

gcc strinitialize.c -o str1

To compile, type

gcc space stringintialize.c space -o space str2

Type

./str1

Now press Enter.

To execute, type ./str2

Output

Type

sting.h

Come back to our program

Suppose here we type the spelling of string as

sting

gcc strinitialize.c -o str1

./str1

We see a fatal error.

sting.h no such file or directory

compilation terminated

This is because the compiler is not able to find the header file with the name sting.h

Hence it is giving an error.

Let us fix the error.

Type r here.

Now click on Save.

Come back to our terminal.

Compile as before, execute as before.

Yes, it is working!

Type

int

Come back to our program.

Suppose, here, I will type int in place of char.

Now, click on Save .

Let us see what happens.

Come back to our terminal.

Compile as before.

We see an error.

Wide character array initialized from non-wide string

format %s expects argument of type 'char'

But argument 2 has type 'int'

This is because we used %s as the format specifier for string.

And we are initializing it with an integer data type int.

Type char here.

Click on Save.

Let us execute.

Compile as before, execute as before.

Come back to our program.

Type .cpp

We will edit the code here.

First, press shift, ctrl and S key simultaneously on your keyboard.

Now save the file with an extension .cpp

and click on Save.

iostream

#include <string>

Now click on Save.

Now we will delete this declaration.

string strname;

Type string space strname and a semicolon

Click on Save.

cout <<

Delete the closing bracket here.

Type

getline(cin, strname);

At the end, type a semicolon.

cout <<"The string is " <<strname <<"\n";

In place of

printf("The string is %s\n",strname);

Delete the format specifier and \n

Now delete the comma

Type two opening angle brackets, delete the bracket here.

Type two opening angle brackets and within the double quotes type \n

Since we do not use the format specifier in C++, the compiler should know that strname is a string variable.

Here we use getline to extract the characters from the input sequence.

It stores them as a string.

g++ string.cpp -o str1

g++ space string.cpp space -o space str3

and press Enter.

./str1

./str3

Press Enter.

I will enter as Talk To A Teacher

Now press Enter

"The string is Talk To A Teacher"

We can see that the output is similar to our C code.

Now come back to our slides.

In this tutorial we learnt

• Strings

• Declaration of a string

• eg: char strname[30]

• Initialization of a string

• eg: char strname[30] = “Talk To A Teacher”

Assignment

Write a program to print a string using the 2^nd syntax

About the Spoken Tutorial Project

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

Spoken Tutorial Workshops

Conducts workshops using spoken tutorials

Gives certificates to those who pass an online test

For more details, Please write to

contact@spoken-tutorial.org

Acknowledgement

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

Thank You for joining.