C++ File Extensions Explained: A Beginner's Guide

C++ works with file I/O (input/output) operations in this programming language. Let's cover a simple example of how to read from and write to files in C++.

Reading from a File

To read from a file in C++, you typically follow these steps:

1. Include necessary libraries:

cpp

#include <iostream>
#include <fstream> // For file I/O operations
#include <string>        

2. Open a file for reading:

cpp                                                                   std::ifstream inputFile("input.txt");
if (!inputFile) {
    std::cerr << "Error opening file." << std::endl;
    return 1;
}        

3. Read the data from the file:

std::string line;
while (std::getline(inputFile, line)) {
    std::cout << line << std::endl; // Output each line to the console
}        

4. Close the file (automatically done when 'inputFile' goes out of scope):

inputFile.close();
        

Writing to a File

To write to a file in C++, you can use similar steps:

1. Open a file for writing:

std::ofstream outputFile("output.txt");
if (!outputFile) {
    std::cerr << "Error opening file." << std::endl;
    return 1;
}        

2. Write data to the file:

outputFile << "Hello, File!" << std::endl;
outputFile << "This is written to a file." << std::endl;        

3. Close the file (automatically done when 'outputFile' goes out of scope):

outputFile.close();
        

Putting it Together

Here's a simple example that reads from an 'input.txt' file and writes to an 'output.txt' file:

#include <iostream>
#include <fstream>
#include <string>

int main() {
    // Reading from input.txt and writing to output.txt
    std::ifstream inputFile("input.txt");
    std::ofstream outputFile("output.txt");

    if (!inputFile || !outputFile) {
        std::cerr << "Error opening files." << std::endl;
        return 1;
    }

    std::string line;
    while (std::getline(inputFile, line)) {
        outputFile << line << std::endl; // Write each line to output.txt
    }

    std::cout << "File copy complete." << std::endl;

    inputFile.close();
    outputFile.close();

    return 0;
}
        

In this example, 'input.txt' is read line by line, and each line is written to output.txt. Error handling is included to check if files are opened successfully. Always ensure that you handle file operations with proper error checking and close files when done.

This example should give you a good starting point for working with files in C++. Feel free to expand and modify it based on your needs and further learning objectives!