Why Solidity is the language of Ethereum in Blockchain / Solidity - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a simple Solidity contract named MyContract.

Blockchain / Solidity

contract [1] {
    // contract code
}

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AMyContract

BEthereum

CSolidity

DBlockchain

Attempts:

3 left

💡 Hint

Common Mistakes

Using reserved words like 'Solidity' or 'Ethereum' as contract names.

Using lowercase or invalid characters in the contract name.

The contract name must be a valid identifier. Here, MyContract is the correct name.

2fill in blank

medium

Complete the code to declare a public state variable of type uint named count.

Blockchain / Solidity

contract Counter {
    [1] public count;
}

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Abool

Buint

Cstring

Daddress

Attempts:

3 left

💡 Hint

Common Mistakes

Using string for numeric values.

Using bool which only holds true or false.

The uint type is used for unsigned integers in Solidity, suitable for counting.

3fill in blank

hard

Fix the error in the function declaration to make it a public function that increments count.

Blockchain / Solidity

contract Counter {
    uint public count;
    function increment() [1] {
        count += 1;
    }
}

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Aprivate

Bexternal

Cpublic

Dinternal

Attempts:

3 left

💡 Hint

Common Mistakes

Using private or internal which restrict access.

Omitting the visibility keyword entirely.

The function must be public to be called from outside the contract.

4fill in blank

hard

Fill both blanks to create a mapping from address to uint named balances and a function to update it.

Blockchain / Solidity

contract Wallet {
    mapping([1] => [2]) public balances;

    function updateBalance(address user, uint amount) public {
        balances[user] = amount;
    }
}

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Aaddress

Buint

Cstring

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using string as key or value in mapping incorrectly.

Using bool which is not suitable for balances.

A mapping in Solidity links keys to values. Here, addresses map to unsigned integers.

5fill in blank

hard

Fill all three blanks to create a function that returns the balance of a given address.

Blockchain / Solidity

contract Wallet {
    mapping(address => uint) public balances;

    function getBalance([1] user) public view returns ([2]) {
        return balances[[3]];
    }
}

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Aaddress

Buint

Cuser

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter types like bool.

Returning the wrong type or using incorrect variable names.

The function takes an address parameter named user and returns a uint balance.