Installation and Configuration
Programming Methodology

Save and Load a List of Numbers from a File in C++

In this exercise, you will create a C++ program that allows the user to input a list of numbers, save them to a text file, and then read and display those numbers from the file. This task will help you understand basic file operations such as writing to and reading from a file using C++. File I/O is an essential skill for storing data persistently in applications. You will use `ofstream` to write the numbers and `ifstream` to read them back. This kind of operation is often used in applications that require logging data or saving user input for later use.

Group

File Management in C++

Objective

1. Prompt the user to enter how many numbers they want to save.
2. Use a loop to collect the numbers from the user and store them in a file using `ofstream`.
3. After saving the numbers, reopen the file using `ifstream`.
4. Read the numbers from the file and display them on the console.
5. Make sure to close the file after each operation.

Implement a program that saves a list of numbers to a file and then reads them.

Example C++ Exercise

 Copy C++ Code 
#include <iostream>     // Include for standard I/O
#include <fstream>      // Include for file stream operations
using namespace std;

int main() {
    string fileName = "numbers.txt"; // File to store the numbers
    int count;                       // Number of values to enter

    // Ask user how many numbers they want to enter
    cout << "How many numbers do you want to save? ";
    cin >> count;

    ofstream outFile(fileName); // Open file for writing

    // Check if the file was opened successfully
    if (!outFile) {
        cout << "Error opening file for writing." << endl;
        return 1; // Exit with error
    }

    // Loop to write numbers to the file
    cout << "Enter " << count << " numbers:" << endl;
    for (int i = 0; i < count; ++i) {
        int num;
        cin >> num;
        outFile << num << " "; // Write each number followed by a space
    }

    outFile.close(); // Close the output file

    ifstream inFile(fileName); // Open file for reading

    // Check if the file was opened successfully
    if (!inFile) {
        cout << "Error opening file for reading." << endl;
        return 1; // Exit with error
    }

    // Read and display the numbers from the file
    cout << "Numbers read from file:" << endl;
    int num;
    while (inFile >> num) {
        cout << num << " "; // Output each number
    }

    inFile.close(); // Close the input file
    cout << endl;

    return 0; // End of program
}

 Output

How many numbers do you want to save? 4
Enter 4 numbers:
12
34
56
78
Numbers read from file:
12 34 56 78

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