Index

Chapter 3: State Variables & Integers

Great job! Now that we've got a shell for our contract, let's learn about how Solidity deals with variables.

State variables are permanently stored in contract storage. This means they're written to the Ethereum blockchain. Think of them like writing to a DB.

Example:

contract Example {
// This will be stored permanently in the blockchain
uint myUnsignedInteger = 100;
}

In this example contract, we created a uint called myUnsignedInteger and set it equal to 100.

Unsigned Integers:
uint
The uint data type is an unsigned integer, meaning its value must be non-negative. There's also an int data type for signed integers.
Note: In Solidity, uint is actually an alias for uint256, a 256-bit unsigned integer. You can declare uints with less bits — uint8, uint16, uint32, etc.. But in general you want to simply use uint except in specific cases, which we'll talk about in later lessons.

Put it to the test

Our Zombie DNA is going to be determined by a 16-digit number.
Declare a uint named dnaDigits, and set it equal to 16.

pragma solidity ^0.4.25;

contract ZombieFactory {

uint dnaDigits = 16;
//start here

}