Question

Write the definition for a void function called text_to_screen that has one formal parameter called \(f\) ile_stream that is of type ifstream. The precondition and postcondition for the function are as follows: //Precondition: The stream file_stream has been connected //to a file with a call to the member function open. //Postcondition: The contents of the file connected to //file_stream have been copied to the screen character by //character, so that the screen output is the same as the //contents of the text in the file. //(This function does not close the file.)

Short answer

Answer: The purpose of the text_to_screen function is to display the contents of a text file connected to the ifstream parameter on the screen.

Step-by-step solution

Function Header Definition

First, define the function header according to the given exercise. The function should be called text_to_screen and it should take one ifstream parameter called \(f\) ile_stream. ```cpp void text_to_screen(ifstream& file_stream); ```

Implement the Function Body

In the function body, read the contents of the file connected to the ifstream and display them on the screen. Since this is a void function, there is no need to return a value. ```cpp void text_to_screen(ifstream& file_stream) { char ch; // Loop through the file_stream and read the characters while (file_stream.get(ch)) { // Print each character to the screen cout << ch; } } ``` Now the complete function definition for the text_to_screen function looks like: ```cpp void text_to_screen(ifstream& file_stream) { char ch; // Loop through the file_stream and read the characters while (file_stream.get(ch)) { // Print each character to the screen cout << ch; } } ```

Key concepts

ifstream in C++

The ifstream object in C++ is an input stream class that allows us to work with files. It stands for 'input file stream' and is used to read data from files on your computer. When using ifstream, the first thing you typically do is to associate it with a file on your system using the open() function.

• An ifstream must be connected to a file before attempting to read from it.
• Upon opening a file, you can read its content using methods such as get(), >>, and getline().
• It is important to always check if the file was successfully opened before trying to read to avoid errors.

Remember, you can think of ifstream as a bridge between your C++ program and the file you wish to read. It’s like having a conversation in which the file speaks to your program through ifstream. Managing the stream correctly ensures that the data flows smoothly from the file to your application.

File I/O

File I/O, which stands for File Input/Output, in C++ refers to the operations that allow a program to read from and write to files. These operations are essential to handle data persistence, enabling programs to store results or read previously written data.

Here are some key points:

• File I/O is performed using stream classes like ifstream for input (reading files), ofstream for output (writing to files), and fstream for both.
• To perform file I/O, a file stream must be opened, the desired operations conducted (read/write), and then the stream must be closed.
• The C++ Standard Library includes several functions and methods that simplify the handling of files, such as open(), close(), eof() (end-of-file), fail(), and more.

In the context of the exercise, the file I/O refers to reading a file character by character, echoing each character to the screen, which is a common operation to display a file's contents directly in the console output.

Function Implementation

Function implementation in C++ involves defining the behavior or the actions that the function should perform when it is called. Every function is declared with a specific purpose, which is fulfilled through its implementation.
In the case of our exercise, the text_to_screen function is a void function, meaning it does not return any value. Instead, its purpose is to perform an action: reading text from a file and displaying it to the screen.

Key aspects of function implementation include:

• The function signature—its return type, name, and parameters—set the blueprint for the function.
• The function body, enclosed in braces {}, contains the code that dictates the function’s behavior.
• Local variables used within the function, such as the 'ch' character in our example, are only accessible within the scope of the function.
• Control structures within the function (like loops or conditionals) determine how the function processes data and reacts under different conditions.

It is advisable to write functions that perform clear, concise tasks, which enhances readability and maintainability of the code. In the exercise solution, the implementation of text_to_screen clearly focuses on a singular task – displaying file contents onto the screen.