Why functions define contract behavior in Blockchain / Solidity - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Solidity function call?

Consider this Solidity contract snippet. What will be the output when getBalance() is called after deploying the contract?

Blockchain / Solidity

contract Wallet {
    uint private balance = 100;

    function getBalance() public view returns (uint) {
        return balance;
    }
}

A 0

B 100

C Compilation error

D Function does not return a value

💡 Hint

Look at the initial value of balance and the return statement.

The function getBalance() returns the private variable balance which is initialized to 100. So the output is 100.

🧠 Conceptual

intermediate

Why do functions define contract behavior in blockchain?

Which of the following best explains why functions define contract behavior in blockchain smart contracts?

A Functions specify the actions and rules the contract can perform and enforce.

B Functions store the contract's data permanently on the blockchain.

C Functions are only used to initialize contract variables once.

D Functions automatically generate user interfaces for the contract.

💡 Hint

Think about what functions do in programming and how contracts interact with users.

Functions in smart contracts define what actions the contract can perform and the rules it enforces. They are the core of contract behavior.

🔧 Debug

advanced

Identify the error in this Solidity function affecting contract behavior

What error will occur when calling withdraw(uint amount) in this contract?

Blockchain / Solidity

contract Bank {
    uint public balance = 50;

    function withdraw(uint amount) public returns (uint) {
        if(amount <= balance) {
            balance -= amount;
        }
        return balance;
    }
}

A No error, function works correctly

B Runtime error: insufficient balance

C Compilation error: missing visibility specifier

D Compilation error: function declared void but returns a value

💡 Hint

Check the function return type and the return statement.

The function withdraw is declared without a return type but tries to return balance. This causes a compilation error.

📝 Syntax

advanced

Which option correctly defines a payable function in Solidity?

Choose the correct syntax for a function that can receive Ether payments.

A function deposit() public pay { /* code */ }

B function deposit() payable { /* code */ }

C function deposit() public payable { /* code */ }

D function deposit() public payable returns (uint) { /* code */ }

💡 Hint

Remember the keyword to allow a function to receive Ether and the required visibility.

The correct syntax requires the payable keyword and a visibility specifier like public. Option C is correct.

🚀 Application

expert

What is the value of 'count' after calling 'increment()' three times?

Given this contract, what is the value of count after calling increment() three times?

Blockchain / Solidity

contract Counter {
    uint public count = 0;

    function increment() public {
        count += 1;
    }
}

A Compilation error

B 0

C 1

D 3

💡 Hint

Each call to increment() adds 1 to count.

Starting from 0, calling increment() three times adds 1 each time, resulting in 3.