Character arrays in C++

Introduction

Character arrays let you store and work with text in C++. They are simple ways to hold words or sentences as a list of letters.

When you want to store a word or sentence in a fixed-size container.

When you need to manipulate text letter by letter.

When you want to pass text to functions that expect C-style strings.

When you want to learn how text is stored in memory at a low level.

When you want to avoid using more complex string classes for simple tasks.

Syntax

C++

char arrayName[size];

// Example:
char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};

The size must be enough to hold all characters plus the special '\0' character that marks the end of the text.

The '\0' character is called the null terminator and tells C++ where the text ends.

Examples

This array holds 5 letters but is missing the '\0' at the end, so it is not a proper C-style string.

C++

char word[5] = {'H', 'e', 'l', 'l', 'o'}; // No null terminator, not a proper string

This array holds the word "Hello" and ends with '\0' so C++ knows where the text ends.

C++

char word[6] = {'H', 'e', 'l', 'l', 'o', '\0'}; // Proper string with null terminator

This array represents an empty string because it only contains the null terminator.

C++

char empty[1] = {'\0'}; // Empty string with only null terminator

This is a shortcut to create a character array with the text "Hi!" and the null terminator.

C++

char greeting[] = "Hi!"; // Size is automatically set to 4 (3 letters + '\0')

Sample Program

This program creates a character array holding "Hello". It prints the word, changes the first letter to 'Y', then prints the new word "Yello". Finally, it prints each letter separately.

C++

#include <iostream>

int main() {
    // Create a character array to hold the word "Hello"
    char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};

    // Print the greeting
    std::cout << "Greeting: " << greeting << std::endl;

    // Change the first letter
    greeting[0] = 'Y';

    // Print the changed greeting
    std::cout << "Changed Greeting: " << greeting << std::endl;

    // Show each character one by one
    std::cout << "Characters: ";
    for (int i = 0; greeting[i] != '\0'; i++) {
        std::cout << greeting[i] << ' ';
    }
    std::cout << std::endl;

    return 0;
}

Important Notes

Time complexity to access or change a character is O(1) because you use the index directly.

Space complexity is fixed by the array size you declare.

Common mistake: forgetting the null terminator '\0' causes unexpected behavior when printing or using string functions.

Use character arrays when you want simple, fixed-size text storage without extra features of std::string.

Summary

Character arrays store text as a list of characters ending with a null terminator '\0'.

Always leave space for the null terminator to mark the end of the text.

You can change characters by accessing array positions directly.