Input and Output: Talking to the World

A program that can't receive anything or show anything would be pretty lonely. Real programs constantly exchange information with the outside world. We have two words for this: input and output.

Input: information coming in

Input is any information that goes into a program. Examples you use every day:

• Typing your password into a login box.
• Tapping a button in an app.
• Speaking to a voice assistant.
• A thermostat reading the room temperature.

All of these are inputs — ways the program receives something to work with.

Output: information going out

Output is any information the program sends out. Examples:

• A message appearing on your screen.
• A sound or song playing.
• A printed receipt.
• A light turning on.

The classic pattern: input, process, output

A huge number of programs follow one simple shape: take some input, process it (do something with it), then produce some output.

Here's a tiny pseudo-code example that asks for a name and greets the person:

ask "What is your name?" into name
show "Hello, " + name + "!"

Reading it as steps:

1. Input: ask the user for their name and store it in the variable name.
2. Process: build a greeting by joining "Hello, " with the name.
3. Output: show the greeting on the screen.

If you typed Maria, it would show: Hello, Maria!