Mastering Blockchain Programming with Solidity

Contract state variables

In the implementation of ERC20, some basic state variables are needed. These state variables store the balance of each Ethereum account, the approved number of tokens and addresses, and the total supply of tokens.

Let's look at each of the state variables defined in the ERC20 token standard. You can refer to the ERC20 implementation code on GitHub at https://github.com/PacktPublishing/Mastering-Solidity/blob/master/Chapter07/contracts/ERC20.sol.