Question

Suppose that infile is an ifstream variable and it is associated with the file that contains the following data: 27306 savings \(7503.35 .\) Write the \(\mathrm{C}++\) statement(s) that reads and stores the first input in the int variable acctNumber, the second input in the string variable accountType, and the third input in the double variable balance.

Short answer

Use `infile >> acctNumber >> accountType >> balance;` to read data.

Step-by-step solution

Include Necessary Headers

To use file streams in C++, include the necessary header at the beginning of your program. Include `#include ` since you are dealing with file input operations.

Declare and Open File Stream

You'll need to declare the ifstream variable `infile` and associate it with the file that contains your data. ```cpp std::ifstream infile("data.txt"); ``` Replace `"data.txt"` with the actual file name if it's different.

Declare Variables to Store Data

Declare the variables needed to store each piece of data extracted from the file. You need an `int` for `acctNumber`, a `string` for `accountType`, and a `double` for `balance`. ```cpp int acctNumber; std::string accountType; double balance; ```

Read Data from the File

Use the `>>` operator to read the data from the `infile` stream into the variables you declared. This operator will automatically skip any whitespace, such as spaces or newlines. ```cpp infile >> acctNumber >> accountType >> balance; ```

Close the File Stream

After reading the needed data, close the file stream using the `close` method to free up system resources. ```cpp infile.close(); ```

Key concepts

fstream

The `` header in C++ is an essential component when dealing with files. When you include this header, you can handle file operations like opening, closing, reading, and writing data to files. This capability is crucial for programs that need to store or retrieve information beyond the duration of the program’s execution.

With ``, you have the flexibility to work with both input and output files. This header provides the tools to manage data not only from files on your desktop but from various storage mechanisms. This gives C++ its powerful file manipulation abilities.

ifstream

`ifstream` is an input file stream class used explicitly for reading data from files. When you declare a variable of type `ifstream`, you establish a connection between your program and a file for input operations. This class is part of the `` header and offers several methods and operators to facilitate file reading.

To start using an `ifstream`, declare an object like `std::ifstream infile;` and link it to your file using `infile.open("filename.txt");`. You can also directly associate a file at the time of declaration. The benefit of using `ifstream` is its ability to handle text and binary files smoothly and securely.

file input

File input refers to the process of reading data from a file into your program. This operation is done using streams that permit data flow between a file and the program. Streams are crucial in file handling as they abstract the complexity involved in managing file data.

The standard way to read data from a file in C++ is by using the extraction operator `>>`. This operator reads data from the `ifstream` stream and stores it into a variable, making it accessible within your program. File input is essential because it allows variables within a program to be initialized with values stored externally.

variable declaration

In C++, variables need to be declared before they are used, specifying the type of data they can hold. Variable declaration involves defining a variable's type and optionally initializing it. This ensures that the program knows what kind of data it will work with.

For the given problem, you will declare three variables: `int acctNumber;`, `std::string accountType;`, and `double balance;`. Each declaration sets aside memory for storing integers, strings, and floating-point numbers, respectively. Proper variable declaration is fundamental in ensuring that the data from the file is stored and manipulated correctly.

data extraction

Data extraction in C++ through `ifstream` involves reading data from a file and storing it into variables. This is commonly done using the extraction operator `>>`, which parses the input stream and converts it to the specified variable type.

During data extraction, the extraction operator automatically trims whitespace and interprets data accurately, making it versatile for varying data formats. In the original problem, `infile >> acctNumber >> accountType >> balance;` is used to extract an integer, a string, and a floating-point number sequentially from the file. Understanding data extraction is key to any C++ program aimed at processing or analyzing external data.