Types of Ethereum Smart Contracts

ERC-20

The ERC-20 standard token is the base due to which many other tokens have appeared. Before the advent of ERC-20, all cryptocurrencies were unique, which complicated the interaction between wallets, projects, exchanges, etc. Its creation made it possible to standardize the issuance of other tokens. To make their token, programmers no longer need to write complex code, just describe only 6 functions:

Total Supply, which determines the total number of tokens. Upon reaching the maximum, the smart contract ceases to issue them.
balance0f is responsible for the initial transfer of tokens to any address.
transfer - transfer of tokens to individual users.
transfer From - transfer tokens from one user to another.
approve is used to check the smart contract for the possibility of transferring tokens.
allowance is responsible for guaranteeing the availability of a sufficient number of tokens for a particular user to forward them to another address.

ERC-223

ERC-223 tokens are often referred to as an improved version of the ERC-20 protocol. When implementing ERC-223, the function ERC-20 - approve was changed. In this standard, when sending funds to the wrong address, the smart contract returns them to the sender.

ERC-827

Tokens of this standard are the main competitor of ERC-20, while they have more informative functionality. ERC-827 allows you to send not only a certain amount of cryptocurrency, but also transaction data. This standard allows parties to confirm the transaction to a third party, despite the fact that it will not have access to the private key and the security of the blockchain will not be compromised. Token functionality is described in less than 100 lines of code.

ERC-948

The ERC-948 standard token was proposed in March 2018 by Kevin Oukoki. It has a model for managing e-commerce subscriptions. For example, you have a monthly subscription to Netflix. When using ERC-948 tokens, your subscription will be paid within the prescribed period if the appropriate funds are available. Unlike ERC-20, which, when used in this way, will monthly ask the user to confirm the subscription.

ERC-777

This standard is designed to solve several problems. Firstly, it implemented the token Received function, which allows not to use the reapproval approval function, which reduces the transaction time by half. Secondly, its functionality allows you to mark suspicious and incompatible addresses. In addition, the ERC-777 solved the incompatibility problem by using the backward compatibility method, which made it cross-standard compatible on the Ethereum platform.

ERC-721

These tokens were created specifically for an online game. They were first used in the game CryptoKitties, where each of the tokens has its own characteristics. Each of the presented cats is a separate ERC-721 token. As it becomes clear, they were created for collecting.

ERC-821 and ERC-875

They are a continuation of the ERC-721 standard.

ERC-821 implements the function of using more specific naming, so as not to cause confusion between different types of collectibles.

ERC-875 proposed the ability to send multiple NFTs (non-fungible tokens) in one transaction, by assigning each of them a personal index. The standard also provides for secure sending and exchange of tokens, as is the case with ERC-721.