← IGCSE Computer Science Paper 1

Digital ledger

A ledger stored electronically instead of on paper. Records are kept as data on computers, so they are easy to search and copy. Digital currency uses one to track who owns what.

Part of: IGCSE Computer Science 0478 — 5.2 Digital Currency — Module 13

Understanding Digital ledger in IGCSE Computer Science Paper 1

What it does: The list holds one record as data: sender, receiver and amount. This shows that records in a digital ledger are stored as data. Copying data takes a single command, whereas copying a paper ledger would mean rewriting every page by hand.

Common mistakes: A Python list has no add() method. A new record is put on the end of the digital ledger with append(), so the line should be ledger.append("Ava>Ben 5"). A tuple () cannot be changed, so new records cannot be appended to it. A digital ledger that grows needs a list, so it should be ledger = [].

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

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Learning
Duo
Which statement describes a digital ledger?
A ledger stored electronically, with records kept as data on computersA ledger written by hand in a book and kept in a safe
Matches
A digital ledger is a book where records are written by hand with a pen
↓
This describes a paper ledger. A digital ledger is stored electronically, so its records are kept as data on computers.
Applying
Meanings
Term
digital ledger
Meaning
A ledger stored electronically instead of on paper. Records are kept as data on computers, so they are easy to search and copy. Digital currency uses one to track who owns what.
Practice
DECLARE ledger : ARRAY[1:3] OF STRING
Testing
Gaps
[1] ← "Ava pays Ben 5"
Check Answer
Spots
1ledger = []
2ledger.add("Ava>Ben 5")

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Quick Questions

1. Which statement describes a digital ledger?
A. A ledger stored electronically, with records kept as data on computers ✓
B. A ledger written by hand in a book and kept in a safe
A digital ledger does the same job as a paper ledger, but the records are stored as data on computers instead of on paper.
2. What is the main job of a digital ledger?
A. To print new coins and notes
B. To keep a record of transactions ✓
A ledger, whether on paper or digital, is a record of transactions. A digital ledger does not create physical money.
3. Which is an advantage of a digital ledger over a paper ledger?
A. Records are easy to search and copy ✓
B. Records can only be read by one person in one room
Data on a computer can be searched in seconds and copied easily. Finding one entry in a paper book takes much longer.
4. How are records kept in a digital ledger?
A. As ink on pages
B. As data stored on computers ✓
In a digital ledger each record is stored as data. Ink on pages describes a paper ledger.
5. Why does digital currency need a digital ledger?
A. To track who owns what ✓
B. To turn the currency into physical coins
Digital currency has no coins or notes to hold. A digital ledger records transactions so everyone can work out who owns what.

Match the Pairs

digital ledger → A ledger stored electronically as data on computers instead of on paper
ledger.search("Ava") → Finds every record that mentions Ava in a digital ledger
A digital ledger stores each record as data, such as a row in a table, rather than as handwriting on paper → ledger = [["Ava", "Ben", 5]]
Because the records are data, a digital ledger can be copied easily to another computer → backup = ledger.copy()
A digital ledger is a book where records are written by hand with a pen → This describes a paper ledger. A digital ledger is stored electronically, so its records are kept as data on computers.
Digital currency does not need a ledger because there are no coins or notes to track → Digital currency still needs a ledger. With no physical coins or notes, a digital ledger is how the system tracks who owns what.

Key Term

digital ledger
A ledger stored electronically instead of on paper. Records are kept as data on computers, so they are easy to search and copy. Digital currency uses one to track who owns what.

Fill in the Blanks

1. ledger[1] ← "Ava pays Ben 5"
Hint: Type the name of the variable that stores the digital records.
2. OUTPUT ledger[1]
Hint: Type the index number of the first record, since pseudocode arrays start counting here.
3. IF ledger[2] = "Ben pays Cy 3" THEN OUTPUT "Found" ENDIF
Hint: Type the keyword that starts the code run when a searched record matches.
4. backup ← ledger OUTPUT backup[1]
Hint: Type the assignment operator that copies the records into the new variable.
5. owner ← ledger[3] OUTPUT "Coin 7 is owned by " & owner
Hint: Type the variable that holds the ownership record read from the ledger.

Spot the Error

Question 1
A ledger = []
B ledger.add("Ava>Ben 5")
C print(len(ledger))
Line B — A Python list has no add() method. A new record is put on the end of the digital ledger with append(), so the line should be ledger.append("Ava>Ben 5").
Question 2
A ledger = ()
B ledger.append("Zoe>Leo 3")
C print(ledger[0])
Line A — A tuple () cannot be changed, so new records cannot be appended to it. A digital ledger that grows needs a list, so it should be ledger = [].
Question 3
A ledger = []
B ledger.append("Mia>Noah 2")
C ledger.append("Noah>Isla 1")
D print(ledger.len())
Line D — Lists do not have a len() method. To count the records stored in the digital ledger, use the len() function: print(len(ledger)).
Question 4
A ledger = ["A>B 5" "B>Z 2"]
B for rec in ledger:
C if "B" in rec:
D print(rec)
Line A — The comma between the two records is missing. Items in a list must be separated by commas so each record is stored separately and can be searched.
Question 5
A ledger = ["A>B 5"]
B backup = ledger.copy()
C print(backup = ledger)
Line C — A single = assigns a value and cannot be used inside print() to compare. To check that the copy matches the original ledger, use ==.

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