Writing Functions to Reuse a Block of Code

Hey there! I'm Byte, and today we're going to talk about one of the most powerful tricks in programming — functions. Imagine you bake cookies every day. Every single day you write out the same steps: preheat oven, mix ingredients, bake 12 minutes. That's exhausting and wasteful! A smarter cook writes the recipe once on a card, names it 'bakeCookies', and just reads from the card each time. Functions work exactly like that recipe card. A **function** packages a set of steps under a single name. Whenever your program needs those steps, it **calls** the function by name instead of repeating every line. Functions get even more powerful with **parameters** — slots where you plug in different values each time. Here's an example in Python: ``` def greet(name): print("Hello, " + name + "!") greet("Aisha") # prints: Hello, Aisha! greet("Marcus") # prints: Hello, Marcus! ``` The word `def` tells Python we are *defining* a function. `greet` is its name. `name` is the parameter — a placeholder that takes a different value every call. The indented line underneath is the **body**: the steps that run each time. Notice we wrote the printing logic only once, but used it twice with different names. If we ever want to change the greeting, we change it in one place and every call updates automatically. That's the superpower of functions: **write once, reuse many times**. Hint: When you call a function, think 'What value am I handing to the parameter?' — that value is called an **argument**. Arguments are values you supply at call time; they are not part of the function definition itself.