← IGCSE Computer Science Paper 1

Blocks of transactions

A group of transaction records saved together with a time-stamp as one unit of the blockchain. When a block is full it is closed, and new transactions go into a new block.

Part of: IGCSE Computer Science 0478 — 5.2 Digital Currency — Module 19

Understanding Blocks of transactions in IGCSE Computer Science Paper 1

What it does: The list holds three transaction records, all saved together as one block. Once the block is full it is closed, so a new block is started to hold the next transactions. Each block has a time-stamp that shows when it was saved. Passwords are never stored in a block. The blockchain is the whole chain of blocks, and each block stores several transactions together.

Common mistakes: The closing bracket is missing. It should be block.add(transaction1) so the first transaction is added to the block. Once a block is full it must be closed, not opened. The line should be block.close().

Class: _____________________  ·  Name: _____________________  ·  Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add Blocks of transactions to a class →

This module's key terms are also in a printable crossword (Modules 510–519) and word search (Modules 510–546).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning
Duo
Which statement describes a block in a blockchain?
A group of transaction records saved together as one unitA single coin that is stored in a digital wallet
Matches
Every transaction is saved in its own blockchain instead of in a block
↓
A blockchain is made of many blocks, and each block holds a group of transactions. Transactions are not each saved in a separate blockchain.
Applying
Meanings
Term
block
Meaning
A group of transaction records saved together with a time-stamp as one unit of the blockchain. When a block is full it is closed, and new transactions go into a new block.
Practice
block7 ← NEW BLOCK
Testing
Gaps
block.()
Check Answer
Spots
1block ← new Block()
2block.add(transaction1

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

The 'Pufferfish' badge — Error Handler, one of Cloodit's 106 collectible badges
Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy
Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games
Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print
Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. Which statement describes a block in a blockchain?
A. A group of transaction records saved together as one unit ✓
B. A single coin that is stored in a digital wallet
A block holds a group of transaction records. It is one unit of the blockchain, not a coin.
2. How many transactions can one block hold?
A. Only ever one transaction
B. Several transactions ✓
A block groups several transactions together, so they can be saved as one unit.
3. What is saved with the transaction records in a block?
A. A time-stamp ✓
B. The password of every user
Each block has a time-stamp that shows when it was saved. Passwords are never stored in a block.
4. What does the time-stamp of a block show?
A. The total value of all the coins in the world
B. The date and time the block was saved ✓
The time-stamp records when the block was created and saved. It does not show a total value.
5. What happens when a block is full?
A. It is closed and no more transactions are added ✓
B. It keeps growing so more transactions can be added
A full block is closed. Its records are saved as one unit and no more can be added.

Match the Pairs

block → A group of transaction records saved together, with a time-stamp, as one unit of the blockchain
block_timestamp → The date and time recorded for the whole block when its group of transactions was saved
Several transactions can be stored together in one block → block = [transaction1, transaction2, transaction3]
When a block is full it is closed, and new transactions go into a new block → if block_full: close(block); block = new_block()
Every transaction is saved in its own blockchain instead of in a block → A blockchain is made of many blocks, and each block holds a group of transactions. Transactions are not each saved in a separate blockchain.
A full block is reopened so extra transactions can be added to it → A full block is closed and is not reopened. New transactions must go into a new block.

Key Term

block
A group of transaction records saved together with a time-stamp as one unit of the blockchain. When a block is full it is closed, and new transactions go into a new block.

Fill in the Blanks

1. IF block.isFull THEN block.close() ENDIF
Hint: Type the method that closes a block once it is full
2. block.timestamp ← NOW() block.add(transaction1) block.add(transaction2)
Hint: Type the property that stores when the block was saved
3. IF block.isFull THEN newBlock ← NEW Block() newBlock.add(transaction4)
Hint: Type the method that puts a transaction into the new block
4. block.add(transaction1) block.add(transaction2) block.add(transaction3)
Hint: Type the variable for the one block that holds several transactions
5. IF block.count >= 3 THEN block.close() block ← NEW Block()
Hint: Type the operator that checks the block count has reached its limit

Spot the Error

Question 1
A block ← new Block()
B block.add(transaction1
C block.add(transaction2)
D block.timestamp ← now()
Line B — The closing bracket is missing. It should be block.add(transaction1) so the first transaction is added to the block.
Question 2
A WHILE block.count < 5
B block.add(nextTransaction)
C ENDWHILE
D block.open()
Line D — Once a block is full it must be closed, not opened. The line should be block.close().
Question 3
A IF block.isFull() THEN
B block.close()
C block.reopen()
D ENDIF
Line C — New transactions go into a new block after the full block is closed. A closed block is never reopened. The line should be block ← new Block().
Question 4
A block ← new Block()
B block.timestamp = now()
C block.add(transaction1)
Line B — In this pseudocode, assignment uses the ← arrow, not =. It should be block.timestamp ← now().
Question 5
A FOR i ← 1 TO 3
B block.add(transaction[i])
C NEXT j
D OUTPUT block.count
Line C — The loop variable is i, so the loop must end with NEXT i. This adds several transactions to one block.

Student with a class code? Join your class →