Why Ethereum enables programmable money in Blockchain / Solidity - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a simple Ethereum smart contract that stores a number.

Blockchain / Solidity

contract SimpleStorage {
    uint256 public [1];
}

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AstoredData

Bvalue

Cnumber

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using names that are too generic or reserved keywords.

The variable storedData is a common name used to store data in simple contracts.

2fill in blank

medium

Complete the code to create a function that sets the stored number.

Blockchain / Solidity

function set(uint256 x) public {
    [1] = x;
}

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AstoredData

Bdata

Cvalue

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not declared in the contract.

The function sets the value of the variable storedData to the input x.

3fill in blank

hard

Fix the error in the function to return the stored number correctly.

Blockchain / Solidity

function get() public view returns (uint256) {
    return [1];
}

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Avalue

BstoredData

Cnumber

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Returning a variable that is not declared or misspelled.

The function returns the value of storedData, which holds the stored number.

4fill in blank

hard

Fill both blanks to create a mapping that stores balances and a function to update it.

Blockchain / Solidity

mapping(address => uint256) public [1];

function updateBalance(address user, uint256 amount) public {
    [2][user] = amount;
}

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Abalances

Baccounts

Dledger

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the mapping and in the function.

The mapping balances stores the balance for each address, and the function updates it.

5fill in blank

hard

Fill all three blanks to create a function that transfers tokens between users.

Blockchain / Solidity

function transfer(address to, uint256 amount) public {
    require([1][msg.sender] >= amount, "Insufficient balance");
    [2][msg.sender] -= amount;
    [3][to] += amount;
}

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Abalances

Baccounts

Dledger

Attempts:

3 left

💡 Hint

Common Mistakes

Using different mapping names causing errors.

The function checks the sender's balance in balances, subtracts the amount, and adds it to the recipient's balance.