Type Checking

Type checking is the step in which a programming language confirms that each piece of data in a program is used in a way that fits its type, so that, for example, text is not mistakenly added to a number or an amount is not passed where an address is expected. Static type checking happens before the program runs, usually when code is compiled, and is used by languages such as Rust, Java and TypeScript. Dynamic type checking happens while the program runs, as in Python and plain JavaScript, which is more flexible but can let errors surface only in use. Strict type checking is especially valued in finance and blockchain, where a bug can move real money and deployed smart contracts are hard to change. Solidity is statically typed, and some newer contract languages use richer type systems to prevent whole classes of mistakes.