Ethereum Virtual Machine (EVM) in Blockchain / Solidity - Mini Project: Build & Apply

Understanding Ethereum Virtual Machine (EVM) Basics

📖 Scenario: You are learning how the Ethereum Virtual Machine (EVM) executes smart contracts. To understand this, you will create a simple Solidity contract that stores and retrieves a number. This simulates how data is stored and accessed on the blockchain through the EVM.

🎯 Goal: Build a simple Solidity smart contract that stores a number and allows reading it back. This will help you understand how the EVM handles contract storage and function calls.

📋 What You'll Learn

Create a Solidity contract named SimpleStorage

Add a state variable storedNumber of type uint

Add a function storeNumber that takes a uint parameter and saves it to storedNumber

Add a function retrieveNumber that returns the current value of storedNumber

Print the retrieved number after storing it

💡 Why This Matters

🌍 Real World

Smart contracts on Ethereum use the EVM to store and manage data securely and transparently. Understanding how to store and retrieve data is fundamental to building decentralized applications.

💼 Career

Blockchain developers must know how to write Solidity contracts that interact with the EVM. This project builds foundational skills for creating and testing smart contracts.

1

Create the Solidity contract and state variable

Write a Solidity contract named SimpleStorage. Inside it, declare a state variable called storedNumber of type uint to hold a number.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract SimpleStorage {
    // Declare storedNumber here
}

Need a hint?

Use contract SimpleStorage { } to start the contract and uint storedNumber; to declare the variable.

2

Add a function to store a number

Inside the SimpleStorage contract, add a public function named storeNumber that takes a uint parameter called num and assigns it to storedNumber.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract SimpleStorage {
    uint storedNumber;

    // Add storeNumber function here
}

Need a hint?

Define function storeNumber(uint num) public { storedNumber = num; } inside the contract.

3

Add a function to retrieve the stored number

Add a public view function named retrieveNumber inside SimpleStorage that returns the current value of storedNumber as a uint.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract SimpleStorage {
    uint storedNumber;

    function storeNumber(uint num) public {
        storedNumber = num;
    }

    // Add retrieveNumber function here
}

Need a hint?

Use function retrieveNumber() public view returns (uint) { return storedNumber; } to read the stored number.

4

Test storing and retrieving a number

Write a script or test code that creates an instance of SimpleStorage, calls storeNumber(42), then calls retrieveNumber() and prints the returned value.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract SimpleStorage {
    uint storedNumber;

    function storeNumber(uint num) public {
        storedNumber = num;
    }

    function retrieveNumber() public view returns (uint) {
        return storedNumber;
    }
}

// Call storeNumber(42) and print retrieveNumber() result
// Your code here

Need a hint?

After deploying, call storeNumber(42) then retrieveNumber() to see 42 returned.