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User Input

Definition of User Input:​

User input refers to the data that a user enters into a program, typically through the keyboard. This data can then be processed and used by the program. Most languages provide functions or methods to read this input.

C++​

Syntax for User Input:​

In C++, the std::cin object is used to read user input from the console.

  • Input is stored directly into a variable using the extraction operator >>.
  • For full-line input, std::getline() can be used (especially for strings with spaces).

Example​

#include <iostream>
#include <string>

int main() {
    std::string name;
    int age;

    // Ask the user for their name
    std::cout << "Enter your name: ";
    std::getline(std::cin, name);  // Read user input as a full line

    // Ask the user for their age
    std::cout << "Enter your age: ";
    std::cin >> age;  // Read user input as an integer

    // Display a message using the user's input
    std::cout << "Hello " << name << ", you are " << age << " years old." << std::endl;

    return 0;
}
 NOTE : Use std::getline() for reading strings with spaces. If mixing std::cin and std::getline(),
 be careful of leftover newline characters in the input buffer.

C#​

Syntax for User Input:​

In C#, the Console.ReadLine() method is used to read user input as a string.

  • To convert the input to other types, use methods like int.Parse(), Convert.ToInt32(), etc.

Example​

using System;

class Program
{
    static void Main()
    {
        // Ask the user for their name
        Console.Write("Enter your name: ");
        string name = Console.ReadLine();  // Read user input as a string

        // Ask the user for their age
        Console.Write("Enter your age: ");
        int age = int.Parse(Console.ReadLine());  // Convert the input to an integer

        // Display a message using the user's input
        Console.WriteLine($"Hello {name}, you are {age} years old.");
    }
}

Java​

Syntax for User Input:​

In Java, you typically use the Scanner class to take user input. You must import java.util.Scanner.

Example​

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        // Create a Scanner object to read user input
        Scanner scanner = new Scanner(System.in);

        // Ask the user for their name
        System.out.print("Enter your name: ");
        String name = scanner.nextLine();  // Read the user's name

        // Ask the user for their age
        System.out.print("Enter your age: ");
        int age = scanner.nextInt();  // Read the user's age

        // Display the message using the input
        System.out.println("Hello " + name + ", you are " + age + " years old.");
        
        // Close the scanner to prevent resource leaks
        scanner.close();
    }
}

Python​

Syntax for User Input:​

In Python, the input() function is used to get user input. By default, the input() function returns the input as a string. You can convert it to other types using int(), float(), etc.

Example​

# Ask the user for their name
name = input("Enter your name: ")

# Ask the user for their age
age = int(input("Enter your age: "))  # Convert input to integer

# Display the message using the user's input
print(f"Hello {name}, you are {age} years old.")

JavaScript​

Syntax for User Input:​

In JavaScript, the prompt() method is commonly used in browsers to take user input, returning the input as a string.

Example​

// Ask the user for their name
let name = prompt("Enter your name:");

// Ask the user for their age
let age = parseInt(prompt("Enter your age:"));  // Convert input to integer

// Display the message using the user's input
alert("Hello " + name + ", you are " + age + " years old.");

TypeScript​

Syntax for User Input:​

TypeScript does not directly support user input like prompt() in browser-based JS or readline in Node.js.

Alternative (in Node.js):

Example​

import * as readline from 'readline';

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

rl.question('Enter your name: ', (name) => {
  console.log(`Hello, ${name}`);
  rl.close();
});

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