C++ Count, Cin, endl

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Basic Input and Output (I/O)

In C++, input and output (I/O) operations are fundamental for interacting with users and handling data. These operations utilize streams, which provide a way to process sequences of bytes.

Key Concepts of C++ I/O

1. Streams: A stream is a flow of data. In C++, streams are used to handle input and output operations. There are different types of streams for different purposes:

     • Input Stream: Handles data coming into the program (e.g., std::cin).

     • Output Stream: Handles data going out of the program (e.g., std::cout).

2. Stream Operations:

     • Input Operation: Reads data from an input stream.

     • Output Operation: Writes data to an output stream.

Important Header Files for I/O

1. <iostream>:

• Purpose: Defines objects for standard I/O operations.

Key Components:

‣ std::cin: Standard input stream (e.g., keyboard input).

‣ std::cout: Standard output stream (e.g., console output).

‣ std::cerr: Standard error stream (e.g., error messages).

2. <iomanip>:

• Purpose: Provides facilities for formatted I/O operations.

Key Functions:

‣ std::setw(int width): Sets the width of the next input/output field.

‣ std::setprecision(int precision): Sets the decimal precision for floating-point numbers.

3. <fstream>:

• Purpose: Handles file input and output.

• Key Classes:

‣ std::ifstream: Input file stream (for reading files).

‣ std::ofstream: Output file stream (for writing to files).

‣ std::fstream: File stream (for both reading and writing).

I/O Library Header Files

cout (Standard Output Stream)

• Definition: cout is an instance of the ostream class and is used for outputting data to the standard output device, typically the console.

• Header File: <iostream>

• Operator: The stream insertion operator (<<) is used with cout to send data to the output stream.

• Buffering: cout is buffered, meaning that output is collected in a buffer and written to the console in chunks rather than character-by-character. This improves performance, especially with multiple output operations.

Example:

#include <iostream>
using namespace std;

int main() {
    int age = 25;
    double height = 5.9;
    cout << "Age: " << age << std::endl;
    cout << "Height: " << height << " feet" << std::endl;
    return 0;
}

Output:

Age: 25
Height: 5.9 feet

cin (Standard Input Stream)

‣ Definition: cin is an instance of the istream class and is used for inputting data from the standard input device, typically the keyboard.

‣ Header File: <iostream>

‣ Operator: The stream extraction operator (>>) is used with cin to extract data from the input stream and store it in a variable.

‣ Buffering: cin is also buffered, which means input is collected in a buffer and processed in chunks. Input operations are typically blocking, meaning the program waits for the user to provide input before continuing.

Example:

#include <iostream>
using namespace std;

int main() {
    int age;
    cout << "Enter your age: ";
    cin >> age;
    cout << "You entered: " << age << std::endl;
    return 0;
}

Output:

Enter your age: 10 You entered: 10

endl (End of Line)

• Definition: endl is a manipulator of the ostream class that inserts a newline character (\n) into the output stream and flushes the stream.

• Header File: <iostream>

• Function: endl not only adds a newline character but also ensures that the buffer is flushed immediately. This is useful for ensuring that output is displayed promptly.

Example:

#include <iostream>
using namespace std;

int main() {
    cout << "Line 1" << std::endl;
    cout << "Line 2" << std::endl;
    cout << "Line 3" << std::endl;
    return 0;
}

Output:

Line 1 Line 2 Line 3

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