Programming fundamentals: think before writing code

The smallest model

Every program receives information, transforms it, and produces a result. Write those three parts before choosing a language.

A variable names data; a type limits meaningful operations; a function encapsulates a transformation.

• Input: what the program needs.
• Process: the applied rules.
• Output: the observable result.

function calculateTotal(price, quantity) {
  const subtotal = price * quantity;
  return subtotal * 1.21;
}

Control flow

A condition chooses a path. A loop repeats a rule. Use them when the domain needs them, not to show that you know the syntax.

function canEnter(age, hasTicket) {
  if (age < 18) return false;
  return hasTicket;
}

Functions people can understand

A good function has a concrete name, explicit inputs, and a predictable output. If it needs a very long explanation, it probably does more than one thing.