File open and close operations in C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the fstream library in C++?

The fstream library provides classes and functions to perform file input and output operations, such as opening, reading, writing, and closing files.

beginner

How do you open a file for writing in C++?

You create an ofstream object and pass the file name to its constructor or use the open() method. For example: <br>std::ofstream file("example.txt");

beginner

Why is it important to close a file after opening it?

Closing a file releases the system resources associated with it and ensures that all data is properly saved and flushed from buffers to the file.

intermediate

What happens if you try to open a file that does not exist using ifstream?

The file will not open, and the ifstream object will be in a failed state. You can check this using is_open() or by testing the stream in a boolean context.

beginner

Show a simple C++ code snippet to open a file, write "Hello" to it, and then close it.

std::ofstream file("greeting.txt");
if (file.is_open()) {
    file << "Hello";
    file.close();
}

Which C++ class is used to read from a file?

A iostream

B ofstream

C ifstream

D fstream

The ifstream class is used specifically for reading from files.

What method do you use to check if a file was successfully opened?

A is_open()

B open()

C close()

D read()

The is_open() method returns true if the file is open.

What happens if you forget to close a file after writing?

A Data may not be saved properly

B File is deleted automatically

C Program crashes immediately

D Nothing happens

Not closing a file can cause data to remain in buffers and not be saved to disk.

Which header file must you include to use file streams in C++?

A <cstdio>

B <iostream>

C <fstream.h>

D <fstream>

The standard header for file streams is <fstream>.

How do you open a file for both reading and writing?

A Use <code>ifstream</code> only

B Use <code>fstream</code> with appropriate mode flags

C Use <code>ofstream</code> only

D Use <code>iostream</code>

The fstream class can open files for both reading and writing by specifying mode flags.

Explain the steps to open a file, write data, and close it in C++.

Think about the order of operations and the classes used.

What are the consequences of not closing a file after finishing file operations?

Consider what happens to data and system resources.