Functions: Reusable Code Blocks

A function bundles a set of instructions into a named, reusable block — write it once, then call it whenever you need it!

🧩Write It Once, Use It Again & Again

✏️1. DEFINE the function

# make a block called jump

function jump() {

bend knees

push off ground

land softly

}

You write the steps one time and give the block a name: jump().

▶️2. CALL it whenever

# use it as many times

# as you want!

jump()  # ⬆ hop 1

jump()  # ⬆ hop 2

jump()  # ⬆ hop 3

To call a function is to run it. No need to rewrite those 10 lines each time!

⚙️Inputs In, Answer Out

A parameter is the input a function expects. The value you actually hand it is the argument. When it finishes, it can send back a return value.

moveForward(5)

argument is 5 → moves 5 steps

moveForward(20)

argument is 20 → moves 20 steps

🪜Decomposition: Big Job → Small Blocks

🤖 Real-world clue: a vending machine is like a function — give it an input (code B4) and it hands back a snack. Press a TV remote button (a function!) again any time, without knowing how it works inside.

🔑Key Terms

🧩Function A named block of code that does a task and can be reused.

📥Parameter An input the function expects when it runs.

🎯Argument The actual value you pass in for a parameter.

📤Return Value The output a function sends back when it finishes.

▶️Call To run or use a function in your code.

🪜Decomposition Breaking a big problem into smaller, manageable parts.

⭐ Remember: write a function once, then call it as many times as you like — and break big problems into small functions to keep your code tidy!

✏️ Computer Science Anchor Chart · Functions: Reusable Code Blocks