Understanding the Strings in C++

In this lesson, you will learn

• C-style strings
• C++ std::string class

In C++, strings can be created in two main ways: using C-style strings (character arrays) and using the C++ std::string class. Let’s go through both methods with examples.

1. C-Style Strings (Character Arrays)

In C++, C-style strings (character arrays) can be created in various ways. Here are the different methods:

1. Direct Initialization

You can directly initialize a character array with a string literal. The compiler automatically adds the null terminator ('\0').

Example:

#include<iostream>

int main() {
    // Direct initialization with a string literal
    char str[] = "Hello, World!";
    
    std::cout << "C-style string: " << str << std::endl;
    return 0;
}

Explanation:

• The character array str is automatically sized to include the null terminator ('\0').
• The string literal "Hello, World!" is stored in the array str.

2. Character-by-Character Initialization

You can manually assign each character to specific positions in the array and ensure you include the null terminator at the end.

Example:

#include<iostream>

int main() {
    // Character-by-character initialization
    char str[6]; // Array size must be at least 6 (5 characters + 1 null terminator)
    str[0] = 'H';
    str[1] = 'e';
    str[2] = 'l';
    str[3] = 'l';
    str[4] = 'o';
    str[5] = '\0'; // Null terminator
    
    std::cout << "C-style string: " << str << std::endl;
    return 0;
}

Explanation:

• The array size must be specified, and it should be large enough to hold the characters and the null terminator.
• You need to manually place the null terminator ('\0') to indicate the end of the string.

3. Partial Initialization

You can partially initialize a character array and leave the rest uninitialized. However, you must include the null terminator manually.

Example:

#include<iostream>

int main() {
    // Partial initialization
    char str[10] = {'H', 'e', 'l', 'l', 'o', '\0'};
    
    std::cout << "C-style string: " << str << std::endl;
    return 0;
}

Explanation:

• The first five elements are initialized with characters, and the sixth element is the null terminator.
• The remaining elements of the array remain uninitialized but are irrelevant because the string ends at the null terminator.

4. String Copy using strcpy

You can create an empty character array and then copy a string into it using the strcpy function from the C library.

Example:

#include<iostream>
#include<cstring>  // Include the C string library

int main() {
    // Creating an empty character array
    char str[20];
    
    // Copying a string using strcpy
    strcpy(str, "Hello, World!");
    
    std::cout << "C-style string: " << str << std::endl;
    return 0;
}

Explanation:

• strcpy is used to copy the string "Hello, World!" into the character array str.
• The array str should be large enough to hold the copied string and the null terminator.

2. C++ Style String(Using string class)

C++ provides a std::string class in the Standard Library, which simplifies string manipulation by automatically handling memory management and providing various functions for string operations.

Example: Creating String in C++

#include<iostream>
#include<string>
using namespace std;

int main() {
    // Creating a C++ string
    string str1 = "Hello, World!";
    
    // You can also declare an empty string and assign a value later
    string str2;
    str2 = "Hello";
    
    // Concatenating strings
    string str3 = str2 + ", C++!";

    //Creates a copy of another string
    string str4 = str3;

    //Creates a string with multiple repetitions of a character
    string str5(5, 'A');  // "AAAAA"
    
    // Printing C++ strings
    cout << "C++ string 1: " << str1 <<endl;
    cout << "C++ string 2: " << str2 <<endl;
    cout << "Concatenated C++ string: " << str3 <<endl;
    cout << "Copy String: " << str4 <<endl;
    cout << "Repetitions of a character: " << str5 <<endl;

    return 0;
}

Output

C++ string 1: Hello, World!
C++ string 2: Hello
Concatenated C++ string: Hello, C++!
Copy String: Hello, C++!
Repetitions of a character: AAAAA

Key Differences between C-Style and C++ Style Strings

Here’s a summary table that outlines the key differences between C-style strings and C++-style strings.

End of the lesson….enjoy learning

Student Ratings and Reviews

Submit a Review