Introduction

Goal of the Tutorial

This tutorial aims to provide a comprehensive understanding of the architecture of decentralized applications (dApps). By the end of this guide, you would have a complete understanding of the three fundamental layers that make up dApps, namely, the blockchain layer, the contract layer, and the application layer.

Learning Outcomes

• You will understand what dApps are.
• You will gain knowledge about the three-layer architecture of dApps.
• You will learn how these layers interact with each other.
• You will view and understand practical code examples.

Prerequisites

Basic knowledge of blockchain technology and familiarity with a programming language, preferably JavaScript, would be beneficial but not necessary.

Step-by-Step Guide

1. Understanding dApps

Decentralized applications, or dApps, are applications that run on a P2P network of computers rather than a single computer. Unlike traditional applications, they are open-source, autonomous, and have their data stored on a blockchain.

2. The Three-Layer Architecture

The structure of a dApp can be broken down into three layers:

1. Blockchain Layer: This is the foundational layer that provides a decentralized database for the dApp. It is responsible for handling transactions and ensuring data consistency across all nodes in the network.

2. Contract Layer: This layer contains the business logic of the dApp, defined in smart contracts. These are self-executing contracts with the terms of the agreement directly written into code.

3. Application Layer: This is the user interface of the dApp. It is responsible for interacting with the user and displaying data.

Code Examples

1. Smart Contract Example (Solidity)

// SPDX-License-Identifier: MIT
pragma solidity ^0.7.4;

contract SimpleStorage {
    uint storedData;

    function set(uint x) public {
        storedData = x;
    }

    function get() public view returns (uint) {
        return storedData;
    }
}

This is a simple smart contract written in Solidity, Ethereum's programming language. It consists of a contract SimpleStorage that contains a single unsigned integer storedData. The contract includes two functions: set() to store a value and get() to retrieve that value.

Summary

In this tutorial, we have covered the basics of dApps and their three-layer architecture. We've also looked at a simple smart contract coded in Solidity.

Next Steps

To further your understanding of dApps, start exploring different types of blockchain platforms like Ethereum, Tron, and EOS. Try building your own simple dApps.

Additional resources

Here are some resources for further reading:
1. Ethereum's official Solidity documentation: https://solidity.readthedocs.io/
2. Truffle Suite for dApp development: https://www.trufflesuite.com/
3. OpenZeppelin for reusable smart contracts: https://openzeppelin.com/

Practice Exercises

1. Exercise 1: Try to write a simple smart contract in Solidity for a voting system.
2. Exercise 2: Try to design a simple user interface for a dApp.
3. Exercise 3: Try to integrate the user interface with the smart contract you wrote in exercise 1.

These exercises should give you a practical understanding of dApp architecture. Good luck with your learning journey!