Solidity is a statically typed language, which means that the type of each variable (state and local) needs to be specified.

There are 3 types of variables in Solidity

• local

  • declared inside a function

  • not stored on the blockchain

• state

  • declared outside a function

  • stored on the blockchain

• global (provides information about the blockchain)

// SPDX-License-Identifier: MIT
pragma solidity ^0.7.3;

contract Variables {
    // State variables are stored on the blockchain.
    string public text = "Hello";
    uint public num = 123;

    function doSomething() public {
        // Local variables are not saved to the blockchain.
        uint i = 456;

        // Here are some global variables
        uint timestamp = block.timestamp; // Current block timestamp
        address sender = msg.sender; // address of the caller
    }
}