Input and Output (I/O) Basics

Input and Output (I/O) is how programs interact with the world around them. Input is any information your program receives, and output is any information it sends out. Understanding I/O is a foundational skill in programming, paving the way for working with files, user interfaces, and network communications.

Objectives

By the end of this lesson, you will:

  • Understand what Input and Output (I/O) mean in programming.
  • Learn how to use basic input and output functions in Python and JavaScript.
  • Prepare to explore File I/O in the next lesson.

1. What is I/O?

I/O stands for Input and Output:

  • Input: Data that the program receives from a user, a file, or another program.
  • Output: Data that the program sends to the screen, a file, or another program.

Think of I/O as a conversation between your program and its environment.

Example Scenarios:

  • Input: A user types their name into a program.
  • Output: The program displays a personalized greeting.

2. Input and Output in Python

Python provides simple and powerful ways to handle I/O.

2.1 Input in Python

The input() function lets you collect data from the user:

# Get input from the user
data = input("What is your name? ")
print("Hello, " + data + "!")

2.2 Output in Python

Use the print() function to display data:

# Output a message
print("Welcome to the world of programming!")

2.3 Formatting Output in Python

Python makes it easy to format output using f-strings:

name = "Alex"
age = 12
print(f"My name is {name} and I am {age} years old.")

3. Input and Output in JavaScript

JavaScript handles I/O in a slightly different way, often working with web browsers or environments like Node.js.

3.1 Input in JavaScript

Use the prompt() function in a browser to get input:

// Get input from the user
const name = prompt("What is your name?");
console.log("Hello, " + name + "!");

In Node.js, you can use the readline module for input:

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

rl.question("What is your name? ", function (name) {
  console.log(`Hello, ${name}!`);
  rl.close();
});

3.2 Output in JavaScript

JavaScript uses console.log() for output:

// Output a message
console.log("Welcome to the world of programming!");

4. Practice Activities

Activity 1: Greeting Program

Write a program that asks the user for their favorite color and then prints a message using that color.

  • Python Example:

    color = input("What is your favorite color? ")
print(f"Wow, {color} is a beautiful color!")

  • JavaScript Example:

    const color = prompt("What is your favorite color?");
console.log(`Wow, ${color} is a beautiful color!`);

Activity 2: Temperature Conversion

Create a program that:

  1. Asks the user for a temperature in Celsius.
  2. Converts it to Fahrenheit.
  3. Prints the result.

  • Python Example:

    celsius = float(input("Enter temperature in Celsius: "))
fahrenheit = (celsius * 9/5) + 32
print(f"{celsius}C is equal to {fahrenheit}F.")

  • JavaScript Example:

    const celsius = parseFloat(prompt("Enter temperature in Celsius:"));
const fahrenheit = (celsius * 9) / 5 + 32;
console.log(`${celsius}C is equal to ${fahrenheit}F.`);

5. What’s Next?

Now that you’ve learned the basics of Input and Output, you’re ready to explore File I/O. In the next lesson, we’ll learn how to read from and write to files, unlocking even more possibilities for interacting with data.

Happy coding!