Why handling value is core to blockchain - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why is value handling essential in blockchain?

Which of the following best explains why handling value is core to blockchain technology?

A Because blockchain speeds up internet connections by handling data packets efficiently.

B Because blockchain enables secure and transparent transfer of digital assets or money without a middleman.

C Because blockchain is mainly used to store large files securely.

D Because blockchain is designed to create complex graphics for video games.

💡 Hint

Think about what blockchain is mostly used for in real life.

Blockchain's main power is to securely move and track digital value like money or assets without needing banks or middlemen.

❓ Predict Output

intermediate

What is the output of this simple blockchain value transfer simulation?

Consider this Python code simulating a simple blockchain transaction ledger. What will be printed?

Blockchain / Solidity

ledger = []

# Add initial balance
ledger.append({'address': 'Alice', 'balance': 100})
ledger.append({'address': 'Bob', 'balance': 50})

# Alice sends 30 to Bob
for entry in ledger:
    if entry['address'] == 'Alice':
        entry['balance'] -= 30
    elif entry['address'] == 'Bob':
        entry['balance'] += 30

print(ledger)

A SyntaxError

B [{'address': 'Alice', 'balance': 100}, {'address': 'Bob', 'balance': 50}]

C [{'address': 'Alice', 'balance': 70}, {'address': 'Bob', 'balance': 80}]

D [{'address': 'Alice', 'balance': 130}, {'address': 'Bob', 'balance': 20}]

💡 Hint

Think about how balances change after a transfer.

Alice's balance decreases by 30, Bob's increases by 30, so their balances become 70 and 80 respectively.

🔧 Debug

advanced

Identify the error in this blockchain value update code

What error will this code produce when trying to update balances in a blockchain ledger?

Blockchain / Solidity

ledger = [{'address': 'Alice', 'balance': 100}, {'address': 'Bob', 'balance': 50}]

for entry in ledger:
    if entry['address'] == 'Alice':
        entry['balance'] = entry['balance'] - 30
    elif entry['address'] == 'Bob':
        entry['balance'] += '30'

print(ledger)

A KeyError: 'balance'

B SyntaxError: invalid syntax

C No error, output: [{'address': 'Alice', 'balance': 70}, {'address': 'Bob', 'balance': 80}]

D TypeError: unsupported operand type(s) for +=: 'int' and 'str'

💡 Hint

Look carefully at the types used in the addition operation.

The code tries to add a string '30' to an integer balance, causing a TypeError.

📝 Syntax

advanced

Which option correctly defines a blockchain transaction function?

Which of these Python function definitions correctly handles a transaction by deducting from sender and adding to receiver?

A

def transfer(sender, receiver, amount):
    sender['balance'] = sender['balance'] - amount
    receiver['balance'] = receiver['balance'] + amount
    return sender, receiver

B

def transfer(sender, receiver, amount):
    sender['balance'] -= amount
    receiver['balance'] += amount

C

def transfer(sender, receiver, amount):
    sender.balance -= amount
    receiver.balance += amount

D

def transfer(sender, receiver, amount):
    sender['balance'] = sender['balance'] + amount
    receiver['balance'] = receiver['balance'] - amount

💡 Hint

Check for correct syntax and logic for transferring value.

Option A correctly updates balances and returns updated accounts. Option A misses return, C uses dot notation on dict, D reverses logic.

🚀 Application

expert

How many transactions are recorded after this blockchain simulation?

Given this code simulating a blockchain ledger with transactions, how many transactions are recorded in the ledger after running?

Blockchain / Solidity

ledger = []

# Genesis block
ledger.append({'block': 0, 'transactions': []})

# Add transactions
ledger[0]['transactions'].append({'from': 'Alice', 'to': 'Bob', 'amount': 50})
ledger[0]['transactions'].append({'from': 'Bob', 'to': 'Charlie', 'amount': 20})

# Add new block
ledger.append({'block': 1, 'transactions': [{'from': 'Charlie', 'to': 'Alice', 'amount': 10}]})

A 3

B 1

C 2

D 4

💡 Hint

Count all transactions inside all blocks.

Block 0 has 2 transactions, block 1 has 1 transaction, total 3 transactions.