A string is a collection of characters. There are two types of strings commonly used in C++ :
- Strings that are objects of string class (The Standard C++ Library String Class)
- C-strings (C-style Strings)
C-strings
In C programming, the collection of characters is stored in the form of arrays. This is also supported in C++ programming. Hence, it's called C-strings.
C-strings are arrays of type char terminated with a null character, that is, \0 (ASCII value of null character is 0).
How to define a C-string?
char str[] = "C++";
In the above code, str is a string and it holds 4 characters.
Although "C++" has three characters, the null character \0 is added to the end of the string automatically.
Alternative ways of defining a string
char str[4] = "C++";
char str[] = {'C','+','+','\0'};
char str[4] = {'C','+','+','\0'};
Like arrays, it is not necessary to use all the space allocated for the string. For example:
char str[100] = "C++";
Example 1: C++ String to Read a Word
C++ program to display a string entered by user.
#include <iostream>
using namespace std;
int main()
{
char str[100];
cout << "Enter a string: ";
cin >> str;
cout << "You entered: " << str << endl;
cout << "\nEnter another string: ";
cin >> str;
cout << "You entered: " << str << endl;
return 0;
}
Output
Enter a string: C++ You entered: C++ Enter another string: Programming is fun. You entered: Programming
Notice that, in the second example, only "Programming" is displayed instead of "Programming is fun".
This is because the extraction operator >> works as scanf() in C and considers a space " " as a terminating character.
Example 2: C++ String to read a line of text
C++ program to read and display an entire line entered by the user.
#include <iostream>
using namespace std;
int main()
{
char str[100];
cout << "Enter a string: ";
cin.get(str, 100);
cout << "You entered: " << str << endl;
return 0;
}
Output
Enter a string: Programming is fun. You entered: Programming is fun.
To read the text containing blank space, cin.get function can be used. This function takes two arguments.
The first argument is the name of the string (address of the first element of the string), and the second argument is the maximum size of the array.
In the above program, str is the name of the string and 100 is the maximum size of the array.
String Object
In C++, you can also create a string object for holding strings.
Unlike using char arrays, string objects have no fixed length and can be extended as per your requirement.
Example 3: C++ string using string data type
#include <iostream>
using namespace std;
int main()
{
// Declaring a string object
string str;
cout << "Enter a string: ";
getline(cin, str);
cout << "You entered: " << str << endl;
return 0;
}
Output
Enter a string: Programming is fun. You entered: Programming is fun.
In this program, a string str is declared. Then, the string is asked from the user.
Instead of using cin>> or cin.get() function, you can get the entered line of text using getline().
getline() function takes the input stream as the first parameter, which is cin and str as the location of the line to be stored.
Passing String to a Function
Strings are passed to a function in a similar way arrays are passed to a function.
#include <iostream>
using namespace std;
void display(char *);
void display(string);
int main()
{
string str1;
char str[100];
cout << "Enter a string: ";
getline(cin, str1);
cout << "Enter another string: ";
cin.get(str, 100, '\n');
display(str1);
display(str);
return 0;
}
void display(char s[])
{
cout << "Entered char array is: " << s << endl;
}
void display(string s)
{
cout << "Entered string is: " << s << endl;
}
Output
Enter a string: Programming is fun. Enter another string: Really? Entered string is: Programming is fun. Entered char array is: Really?
In the above program, two strings are asked to enter. These are stored in str and str1 respectively, where str is a char array and str1 is a string object.
Then, we have two functions display() that outputs the string onto the string.
The only difference between the two functions is the parameter.
The first display() function takes the char array as a parameter, while the second takes the string as a parameter.
This process is known as function overloading. Learn more about Function Overloading.
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