Performing Binary File I/O in C++

Tutorial 5 of 5

Performing Binary File I/O in C++

1. Introduction

In this tutorial, we will learn how to perform binary file Input/Output (I/O) operations in C++. Binary file I/O allows for a more efficient and precise way to store and retrieve data. By the end of this tutorial, you will be able to read from and write to binary files using C++.

Prerequisites: Basic knowledge of C++ programming and familiarity with basic file I/O operations.

2. Step-by-Step Guide

Binary files store data in a binary format, which is the same format in which the data is held in memory. Unlike text files, binary files are not human-readable. When we say binary files, it generally refers to data files that contain data, not readable characters.

To read and write in binary mode, the file stream objects have the member function open(), which accepts an additional argument for mode. The modes are defined in the ios class, which is the base class for all the file streams in C++. To open a file in binary mode, we use the ios::binary mode.

Reading from a Binary File

To read from a binary file, follow these steps:

Open the file in binary mode.
Read the data from the file.

Writing to a Binary File

To write to a binary file, follow these steps:

Open the file in binary mode.
Write the data to the file.

3. Code Examples

Example 1: Writing to a Binary File

#include <fstream>
#include <iostream>

int main() {
    int number = 12345;
    std::ofstream outputFile;

    // Open the file in binary mode
    outputFile.open("output.bin", std::ios::binary);

    // Write to the file
    outputFile.write((char*)&number, sizeof(number));

    outputFile.close();
    return 0;
}

This program writes an integer to a binary file. outputFile.write((char*)&number, sizeof(number)); writes the binary representation of number to the file.

Example 2: Reading from a Binary File

#include <fstream>
#include <iostream>

int main() {
    int number;
    std::ifstream inputFile;

    // Open the file in binary mode
    inputFile.open("output.bin", std::ios::binary);

    // Read from the file
    inputFile.read((char*)&number, sizeof(number));

    std::cout << "The number is: " << number << std::endl;

    inputFile.close();
    return 0;
}

This program reads an integer from a binary file. inputFile.read((char*)&number, sizeof(number)); reads the binary data from the file into number.

Expected Output for Example 2:

The number is: 12345

4. Summary

In this tutorial, we learned how to perform binary file I/O in C++. We learned how to write to and read from binary files using the write() and read() member functions of the fstream library.

5. Practice Exercises

For further practice, try the following exercises:

Write a program to write an array of integers to a binary file and then read it back.
Write a program to write a custom object to a binary file and then read it back.

Remember, practicing and experimenting is the key to learning programming. Good luck!