Why data location affects cost in Blockchain / Solidity - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the data storage location in a smart contract.

Blockchain / Solidity

contract Storage {
    string public data;
    function setData(string memory [1]) public {
        data = [1];
    }
}

Drag options to blanks, or click blank then click option'

Ainput

Bvalue

Clocation

Dinfo

Attempts:

3 left

💡 Hint

Common Mistakes

Using generic names like 'location' which don't clarify the data being stored.

The parameter name value is commonly used to represent the input data to be stored, which is important for clarity in smart contracts.

2fill in blank

medium

Complete the code to calculate gas cost based on data location.

Blockchain / Solidity

function calculateCost(uint256 [1]) public pure returns (uint256) {
    uint256 cost = [1] * 2000;
    return cost;
}

Drag options to blanks, or click blank then click option'

Aprice

Blocation

Csize

Damount

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'location' as a variable for size, which is confusing.

The variable size represents the amount of data, which affects gas cost.

3fill in blank

hard

Fix the error in the code that calculates cost for storing data in different locations.

Blockchain / Solidity

function getCost(string memory [1]) public pure returns (uint256) {
    if (keccak256(bytes([1])) == keccak256(bytes("storage"))) {
        return 5000;
    } else {
        return 1000;
    }
}

Drag options to blanks, or click blank then click option'

AdataLocation

BlocationData

Cdata

Dloc

Attempts:

3 left

💡 Hint

Common Mistakes

Using a parameter name that does not match the variable inside the function.

The parameter dataLocation clearly indicates the location of data, matching the comparison inside the function.

4fill in blank

hard

Fill both blanks to create a dictionary that maps data locations to their gas costs.

Blockchain / Solidity

mapping(string => uint256) public gasCosts = {
    "storage": [1],
    "memory": [2]
};

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A5000

B1000

C2000

D3000

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the gas costs between storage and memory.

Storage costs more gas (5000) than memory (1000) because storing data permanently is more expensive.

5fill in blank

hard

Fill all three blanks to complete the function that returns gas cost based on data location and size.

Blockchain / Solidity

function computeGasCost(string memory [1], uint256 [2]) public pure returns (uint256) {
    uint256 baseCost = (keccak256(bytes([1])) == keccak256(bytes("storage"))) ? [3] : 1000;
    return baseCost * [2];
}

Drag options to blanks, or click blank then click option'

AdataLocation

BdataSize

C5000

D3000

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter names or incorrect gas cost values.

The function uses dataLocation to check where data is stored, dataSize for the amount of data, and assigns a base cost of 5000 gas for storage.