In C++, strings are used to represent sequences of characters. They can be handled using two primary types: C-style strings and C++ std::string class strings. Understanding both types is essential for effective string manipulation in C++.

1. C-style Strings

C-style strings are arrays of characters terminated by a null character ('\0'). They are part of the C language and can be used in C++ as well. Here’s how they work:

• Declaration: You can declare a C-style string using an array of characters.
• Initialization: Strings can be initialized with string literals.
• Null Terminator: The null character signifies the end of the string.

Example of C-style Strings

#include <iostream>

int main() {
    // Declare and initialize a C-style string
    char str[20] = "Hello, World!";

    // Output the string
    std::cout << str << std::endl; // Output: Hello, World!

    // Accessing individual characters
    std::cout << "First character: " << str[0] << std::endl; // Output: H

    return 0;
}

2. Working with C-style Strings

C-style strings require functions from the <cstring> library for various operations, such as copying, concatenation, and comparison.

Common C-style String Functions

• strlen: Returns the length of the string.
• strcpy: Copies one string to another.
• strcat: Concatenates two strings.
• strcmp: Compares two strings.

Example Using C-style String Functions

#include <iostream>
#include <cstring>

int main() {
    char str1[20] = "Hello";
    char str2[20] = " World!";

    // Concatenate str1 and str2
    strcat(str1, str2);
    std::cout << "Concatenated string: " << str1 << std::endl; // Output: Hello World!

    // Length of the string
    std::cout << "Length of the string: " << strlen(str1) << std::endl; // Output: 13

    // Compare two strings
    if (strcmp(str1, "Hello World!") == 0) {
        std::cout << "Strings are equal." << std::endl;
    } else {
        std::cout << "Strings are not equal." << std::endl;
    }

    return 0;
}

3. C++ std::string Class

The std::string class is part of the C++ Standard Library and provides a more robust and flexible way to handle strings. It manages memory automatically, eliminating the need for manual memory management that comes with C-style strings.

Features of std::string

• Dynamic Size: std::string can grow or shrink dynamically as needed.
• Member Functions: It comes with a variety of member functions for string manipulation, including concatenation, comparison, and searching.
• No Null Terminator: It manages the null terminator internally, simplifying usage.

Example of std::string

#include <iostream>
#include <string>

int main() {
    // Declare and initialize a std::string
    std::string str = "Hello, World!";

    // Output the string
    std::cout << str << std::endl; // Output: Hello, World!

    // Concatenation
    str += " How are you?";
    std::cout << "After concatenation: " << str << std::endl; // Output: Hello, World! How are you?

    // Length of the string
    std::cout << "Length of the string: " << str.length() << std::endl; // Output: 30

    // Accessing individual characters
    std::cout << "First character: " << str[0] << std::endl; // Output: H

    // Finding a substring
    size_t pos = str.find("World");
    if (pos != std::string::npos) {
        std::cout << "\"World\" found at position: " << pos << std::endl; // Output: 7
    }

    // Substring extraction
    std::string sub = str.substr(7, 5); // Extract "World"
    std::cout << "Substring: " << sub << std::endl; // Output: World

    return 0;
}

4. Common Operations with std::string

Here are some common operations you can perform with std::string:

• Concatenation: Use the + operator or += to concatenate strings.
• Length: Use the length() or size() member functions to get the length of the string.
• Accessing Characters: Use indexing (e.g., str[0]) to access individual characters.
• Finding Substrings: Use the find() method to locate a substring within the string.
• Extracting Substrings: Use the substr() method to extract a portion of the string.