Types define representable values and operations, not economic meaning.
LET’S PICTURE IT
A form can require a yes/no answer in one field and a whole number in another.
SEE IT FOR YOURSELF
A valid counter call, step by stepStep 1 / 4
This example begins with count zero and a request to call increment(). No real contract is deployed.
This example begins with count zero and a request to call increment(). No real contract is deployed.Execution follows the code’s input and permission rules. A website button is not the access-control mechanism.The function reads zero, calculates zero plus one, and writes one to persistent storage.The accepted state contains count one. Later reads can inspect it. Events are emitted only if the code implements them.
Animated local teaching model. No wallet, RPC or live blockchain data. Some labels and hashes are abbreviated for readability.
Booleans express conditions
bool values are true or false. They can control branches or record flags. A variable called active does not enforce a permission unless code actually checks it.
Integer widths define ranges
Unsigned integers represent non-negative values, while signed integers include negative values. Widths come in supported bit sizes, with uint as a shorthand for uint256.
Arithmetic has rules
Modern Solidity normally checks overflow and underflow outside unchecked blocks. Integer division discards the fractional component according to the type’s rules, so precision and rounding remain design choices.
Units need separate specification
A uint256 could mean Wei, a token quantity, a counter or a timestamp. Type correctness alone does not prove a caller supplied the intended unit or range for the application.
Read the example
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;
contract LearningExample {
bool public active = true;
uint256 public count = 7;
function setActive(bool next) external {
active = next;
}
}
This intentionally open toy setter demonstrates types, not a production authorization policy.
QUICK CHECK · NO PRESSURE
Does uint256 automatically mean Wei?
The application defines the unit; the type defines numeric representation.