Why gas efficiency saves money in Blockchain / Solidity - See It in Action

Why Gas Efficiency Saves Money

📖 Scenario: You are building a simple smart contract to understand how gas efficiency affects the cost of running blockchain transactions. Gas is the fee paid to execute operations on the blockchain. The less gas your contract uses, the less money you spend.

🎯 Goal: Create a smart contract that stores and updates a number. Then, calculate the gas used for updating the number and see how reducing operations saves gas and money.

📋 What You'll Learn

Create a smart contract with a state variable called storedNumber initialized to 0

Add a function called updateNumber that sets storedNumber to a new value

Add a helper variable called gasUsed to simulate gas consumption

Implement two versions of updateNumber: one with extra unnecessary steps and one optimized

Print the gas used by both versions to compare savings

💡 Why This Matters

🌍 Real World

Blockchain developers must write efficient smart contracts to save users money on transaction fees.

💼 Career

Understanding gas efficiency is essential for blockchain engineers, smart contract developers, and anyone working with decentralized applications.

1

Create the smart contract with a state variable

Create a Solidity contract called GasDemo with a public uint state variable named storedNumber initialized to 0.

Blockchain / Solidity

contract GasDemo {
    // Your code here
}

Need a hint?

Use uint public storedNumber = 0; inside the contract.

2

Add a helper variable to track gas used

Inside the GasDemo contract, add a public uint variable called gasUsed initialized to 0.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract GasDemo {
    uint public storedNumber = 0;
    // Your code here
}

Need a hint?

Declare uint public gasUsed = 0; inside the contract.

3

Add two versions of updateNumber function

Add two public functions inside GasDemo: updateNumberInefficient(uint newValue) and updateNumberEfficient(uint newValue). In updateNumberInefficient, set storedNumber to newValue and increment gasUsed by 15 units to simulate inefficiency. In updateNumberEfficient, set storedNumber to newValue and increment gasUsed by 5 units to simulate efficiency.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract GasDemo {
    uint public storedNumber = 0;
    uint public gasUsed = 0;

    // Your code here
}

Need a hint?

Define both functions with the exact names and update storedNumber and gasUsed as described.

4

Print gas used after calling both functions

Write a public view function called getGasUsedDifference that returns the difference in gas used between calling updateNumberInefficient and updateNumberEfficient. For simplicity, simulate calling both functions with newValue 10 and 20 respectively inside the function and return the difference 10 (which is 15 - 5). Then, write a print statement in comments showing the output 10.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract GasDemo {
    uint public storedNumber = 0;
    uint public gasUsed = 0;

    function updateNumberInefficient(uint newValue) public {
        storedNumber = newValue;
        gasUsed += 15; // 15 units simulating inefficiency
    }

    function updateNumberEfficient(uint newValue) public {
        storedNumber = newValue;
        gasUsed += 5; // less gas used
    }

    // Your code here
}

Need a hint?

Return the fixed difference 10 in the function as a simple simulation.