String in C++ Programming

String in C++

What is String in C++

A String is a sequence of characters. In C++ programming, a string can be created in two ways.

• By using C-Style Character String.
• By using standard String Class.

C-Style Character String

A C-Style Character String uses a Character Array to store sequence of characters.

char variable_name[size]

Here, size is the maximum number of characters that can be store in the character array.

char a[15];

The above character array can store a string up to 15 characters long. You can use any size that fits your requirement.

Declaration and Initialization of a Character Array in C++

In C++ programming a character array can be declared and initialized in 3 ways. Let's see all the three examples.

char data[]= {'H','E','L','L','O','\0'};

In Example 1, we have declared a character array named data and initialize it with the string HELLO. We put a null character (‘\0’) at the end, which specifies the end of the string. So, the actual size of the array is 6, including the null character.

char data[]= "HELLO";

In Example 2, we have used double quotes (") to initialize the word HELLO in the character array. Here we don’t have to specify the null character (‘\0’) because it is added automatically.

Thus, both the examples will look like as given in the picture below.

char data[10]= "HELLO";

In Example 3, we have mentioned the size 10 and then use the quotes (") to initialize the word HELLO in the character array. In this case the array will look like as given in the picture below.

Store Characters in a Character Array

We can store character in a character array using 3 methods:

• Store characters one by one.
• Store a single word string using cin statement.
• Store a multi-word string using cin.get() statement.
• Store a multi-word string using gets() function.

Let’s see all the examples one by one.

data[0]='H';
data[1]='E';
data[2]='L';
data[3]='L';
data[4]='O';
data[5]='\0';

#include <iostream>
#include <conio.h>

using namespace std;

int main()
{
    char data[20];

    cout<<"Enter Name ";
    cin>>data;
    return 0;
}

In example 2, we have used cin statement to take a single word string input from the user.

#include <iostream>
#include <conio.h>

using namespace std;

int main()
{
    char data[20];

    cout<<"Enter Full Name ";
    cin.get(data,20);
    return 0;
}

In example 3, we have used a cin.get() statement to take a multi-word string input from the user. In cin.get() statement, the first argument is the name of the character array and the second argument is the size of the character array.

#include <iostream>
#include <conio.h>
#include <stdio.h>

using namespace std;

int main()
{
    char data[20];

    cout<<"Enter Full Name ";
    gets(data);
    return 0;
}

In example 4, we have used gets() function to take multi-word string input from the user. To use the gets() function we have to include stdio.h header file in our program.

Display Characters from a Character Array

To display all characters from a character array we can use either cout statement or puts() function.

#include <iostream>
#include <conio.h>
#include <stdio.h>

using namespace std;

int main()
{
    char data[20];
    char city[20];

    cout<<"Enter Name ";
    gets(data);
    printf("Enter City ");
    gets(city);
    cout<<"Name: "<<data<<"  City: "<<city;
    return 0;
}

Enter Name Allen Smith
Enter City California
Name: Allen Smith  City: California

Note: In the above example, we have used the cout statement and insertion operator << to print the name and city on the same line on the screen.

#include <iostream>
#include <conio.h>
#include <stdio.h>

using namespace std;

int main()
{
    char data[20];
    char city[20];

    cout<<"Enter Name ";
    gets(data);
    printf("Enter City ");
    gets(city);
    cout<<"Name: ";
    puts(data);
    cout<<"City: ";
    puts(city);
    return 0;
}

Enter Name Allen Smith
Enter City California
Name: Allen Smith
City: California

Note: In the above example, the puts() function print the character array on the screen and then break the line automatically. Using puts() function, we cannot print multiple outputs on the same line. In order to do so, we have to use the cout statement instead of puts() function.

Access Individual Characters from a Character Array

We can access individual characters from a character array using for, while or do while loop.

#include <iostream>
#include <conio.h>
#include <stdio.h>

using namespace std;

int main()
{
    char data[20];
    int i;

    cout<<"Enter Name ";
    gets(data);

    for(i=0; data[i]!='\0'; i++)
    {
        cout<<data[i]<<endl;
    }
    return 0;
}

Enter Name Dremendo
D
r
e
m
e
n
d
o

In the above example, we have run a 'for loop' from 0 until we get null (‘\0’) and then print the individual characters on the screen using cout statement on separate lines.

Two Dimensional Character Array in C++

A Two Dimensional character array is used to store the list of strings. For example a list of country names, list of fruit names, etc.

char variable_name[row_size][column_size];

Here row_size is the number of rows we want to create in a 2D character array and, column_size is the number of maximum characters we want to store in each row.

char list[5][10];

The above 2D character array named list can store 5 strings having maximum 10 characters in each string.

Declaration and Initialization of a Two Dimensional Character Array in C++

In C++ programming a two dimensional character array can be declared and initialized in two ways. Let’s see both ways.

char list[5][10]= {"Apple", "Banana", "Cherry"};

char list[][10]= {"Apple", "Banana", "Cherry"};

Store and Access Strings in a Two Dimensional Character Array

We can store and access string in 2D character array using for loop. Let’s see the example given below.

#include <iostream>
#include <conio.h>
#include <stdio.h>

using namespace std;

int main()
{
    char list[3][10];
    int r;

    //store the name 3 fruits
    cout<<"Enter 3 fruits name"<<endl;
    for(r=0; r<3; r++)
    {
        gets(list[r]);
    }

    //access the name of 3 fruits from the array
    cout<<"\nNames of 3 fruits are"<<endl;
    for(r=0; r<3; r++)
    {
        cout<<list[r]<<endl;
    }
    return 0;
}

Enter 3 fruits name
Apple
Banana
Cherry

Names of 3 fruits are
Apple
Banana
Cherry                

Note: To store and access the above 2D character array we just need to specify the array name along with the row index in square brackets [ ] as shown in the above example.

Standard String Class

The string class type provided in the C++ as a part of the standard library can be used to store a string.

string str;

Here, str is the object of string class type.

string str="Hello World";

Here, we have declared a string type object str and initialize it with the string Hello World.

Input and Print String using getline() Function

We can use getline() function to take input in a string object, and print the string using cout statement. See the example given below.

#include <iostream>
#include <conio.h>

using namespace std;

int main()
{
    string str;
    cout<<"Enter any string"<<endl;
    getline(cin,str);
    cout<<"You have entered: "<<str;
}

Enter any string
Hello World
You have entered: Hello World

The getline() function requires two arguments, first an input stream and second the name of the string object in which we want to take input.

Access Individual Characters from String Object

We can access individual characters from a string object using at() function.

#include <iostream>
#include <conio.h>

using namespace std;

int main()
{
    string str;
    int i;

    cout<<"Enter a word ";
    getline(cin,str);

    for(i=0; i<str.size(); i++)
    {
        cout<<str.at(i)<<endl;
    }
    return 0;
}

Enter a word Hello
H
e
l
l
o

Here, we have first input a word from the keyboard. After that, we run a loop from 0 to less than the size of the string using size() function and then print all the individual characters on the screen using at() function.