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Worked solutions

IB Computer Science SL · Paper 1

Computer Science, Standard Level

Session: November 2020
Marks: 70
Duration: 1 hour 30 min
Calculator: Not allowed
Questions: 9

Keep your copy of the paper open alongside. We don't reproduce the questions: each part below is labelled to match the November 2020 global paper, which your school or the IB can provide.

Practice mode

Hide our working until you've had a go.

Questions 1–6 · 25 marks

Question 1

3 marks

Word processor typing productivity and purpose of technical documentation

System fundamentals

(a)

2 marks

Mail merge / document templates: Automatically populates recipient names, addresses, and standardized salutations into pre-formatted layout fields from an external database or spreadsheet, eliminating manual repetitive retyping.

Mentor tip

Identify mail merge, autocorrect / text macros, or boilerplate templates.

(b)

1 mark

Provides developers, system administrators, and support engineers with detailed architectural specifications, API signatures, installation steps, and hardware dependencies to maintain, troubleshoot, or extend the software.

Mentor tip

State software maintenance, configuration, and troubleshooting for technical personnel.

Question 2

6 marks

Client-server architecture in airport check-in kiosks

Networks

(a)(i)

1 mark

A hardware terminal or software application that requests data, validation, or services from a central server across a network.

Mentor tip

State that a client initiates service requests to a central server.

(a)(ii)

1 mark

A centralized high-performance computer or software process that listens for client requests, manages centralized resources, and returns requested data or services.

Mentor tip

State that a server manages shared resources and services client requests.

(b)

4 marks

Flight database management: Queries flight manifests and passenger records to verify bookings and passport numbers sent from kiosks.
Real-time seat assignment concurrency: Updates seating charts and reserves chosen seats, enforcing transaction locks to prevent double-booking across simultaneous kiosk check-ins.
Boarding pass payload generation: Validates check-in completion and transmits digitized boarding pass data and barcode tokens back to the kiosk printer.

Mentor tip

Explain validating passenger credentials, preventing seat double-booking, and issuing boarding authorization.

Question 3

4 marks

Comparison of direct changeover and parallel running implementation

System fundamentals

4 marks

Direct Changeover:
- Process: The legacy system is decommissioned completely at a set date/time, and the new system takes over all operational responsibilities immediately.
- Trade-off: Incurs the lowest operating costs with zero duplication of effort, but presents catastrophic operational risk if unforeseen critical defects halt production.
Parallel Running:
- Process: Both legacy and new systems operate concurrently for a trial period, processing identical transaction data.
- Trade-off: Guarantees business continuity and provides a safe fallback if the new system fails, but doubles staffing workload and infrastructure operating expenses.

Mentor tip

Contrast operational risk and running expense across both methods.

Question 4

4 marks

CPU machine instruction cycle registers and decoding

Computer organisation

(a)

1 mark

The program is held in primary memory (RAM) while executing.

Mentor tip

State primary memory (RAM).

(b)

1 mark

The Control Unit (CU) of the central processing unit.

Mentor tip

State the Control Unit.

(c)

2 marks

Stores the memory address of the next instruction or data word to be fetched from or written to primary memory (RAM), driving the system address bus.

Mentor tip

Explain holding the target memory address for the address bus.

Question 5

4 marks

Bubble sort algorithm operational mechanics

Computational thinking, problem-solving and programming

4 marks

1) Pass initialization: The algorithm performs multiple sequential passes through the array elements.
2) Pairwise comparison: On each pass, it compares adjacent elements (e.g. A[I] and A[I + 1]).
3) Conditional swap: If the adjacent pair is in the wrong order (e.g. A[I] > A[I + 1] for ascending sort), their values are swapped using an auxiliary temporary variable.
4) Termination: Passes repeat, with the unsorted portion shrinking by one each pass, until a complete pass occurs with zero swaps, confirming the array is sorted.

Mentor tip

Detail sequential passes, adjacent element comparisons, conditional swapping, and termination upon zero swaps.

Question 6

4 marks

Truth table evaluation for composite Boolean expression (A xor B) and not C

Computer organisation

4 marks

Expression: (A XOR B) AND (NOT C)
Inputs A, B, C across all 8 truth table rows:
- A=0, B=0, C=0 -> (0 XOR 0) = 0, NOT 0 = 1 -> 0 AND 1 = 0
- A=0, B=0, C=1 -> (0 XOR 0) = 0, NOT 1 = 0 -> 0 AND 0 = 0
- A=0, B=1, C=0 -> (0 XOR 1) = 1, NOT 0 = 1 -> 1 AND 1 = 1
- A=0, B=1, C=1 -> (0 XOR 1) = 1, NOT 1 = 0 -> 1 AND 0 = 0
- A=1, B=0, C=0 -> (1 XOR 0) = 1, NOT 0 = 1 -> 1 AND 1 = 1
- A=1, B=0, C=1 -> (1 XOR 0) = 1, NOT 1 = 0 -> 1 AND 0 = 0
- A=1, B=1, C=0 -> (1 XOR 1) = 0, NOT 0 = 1 -> 0 AND 1 = 0
- A=1, B=1, C=1 -> (1 XOR 1) = 0, NOT 1 = 0 -> 0 AND 0 = 0
Notice the expression evaluates to 1 strictly for input rows 010 and 100.

(A \oplus B) \land \neg C = 1 ⟺ (A \neq = B) \land (C = 0)

Mentor tip

Compute intermediate terms (A XOR B) and (NOT C) in separate columns before performing the logical AND.

Questions 7–9 · 45 marks

Question 7

15 marks

School LAN infrastructure, router role, throughput bottlenecks, and inventory algorithm

Networks
Computational thinking, problem-solving and programming

(a)

3 marks

Network boundary routing: Connects the internal school LAN to the external public Internet wide area network.
Packet forwarding by IP routing: Examines destination IP addresses on incoming data packets and consults routing tables to forward packets along the optimal physical path.
NAT and gateway services: Translates internal private IPv4 addresses into a public IP address (Network Address Translation) and filters unauthorized incoming traffic.

Mentor tip

Explain connecting LAN to WAN, packet forwarding via routing tables, and NAT translation.

(b)

4 marks

1) Network bandwidth saturation during peak periods: Simultaneous high-volume streaming, cloud software updates, or file downloads by hundreds of students and faculty exceed total available ISP uplink bandwidth.
2) Collisions and wireless channel congestion: Intense Wi-Fi traffic on overlapping radio channels creates packet collisions and signal interference, requiring frequent packet retransmissions.

Mentor tip

Identify peak bandwidth saturation and wireless radio channel interference.

(c)

4 marks

1) State-of-the-art perimeter firewall: Configured with strict packet filtering rules to block unauthorized inbound connection attempts and close vulnerable network ports.
2) Network segmentation with Virtual LANs (VLANs): Isolating sensitive administrative and student record servers on a restricted subnet segregated from student BYOD Wi-Fi traffic.

Mentor tip

Detail firewall access policies and VLAN network isolation.

(d)

4 marks

Algorithm steps to determine items needing replenishment:
1) Open and read the supplies inventory file sequentially until end of file.
2) For each supply record, extract ID, NAME, MAX_QTY, MIN_QTY, and REMAINING_QTY.
3) Evaluate condition: if REMAINING_QTY <= MIN_QTY then:
- Calculate order amount: ORDER_QTY = MAX_QTY - REMAINING_QTY.
- Output ID, NAME, and ORDER_QTY.
4) Close file after all records have been evaluated.

If REMAINING \leq MIN ⟹ ORDER_QTY = MAX - REMAINING

Mentor tip

Check if remaining quantity is at or below minimum, then compute the difference to maximum.

Question 8

15 marks

Website usability, concurrency security in OS, and customer data ethics

System fundamentals
Computer organisation
Resource management

(a)

2 marks

Navigation intuitiveness: Clear, hierarchical menu structure, consistent breadcrumb trails, and effective search functionality.
Visual readability and accessibility: Legible font sizes, strong color contrast between text and background, and responsive layout scaling across mobile and desktop devices.

Mentor tip

Identify navigation structure and visual readability / accessibility contrast.

(b)

2 marks

Color vision deficiencies (color blindness): Relying solely on color (such as red/green status indicators) prevents individuals with protanopia or deuteranopia from distinguishing interface states without accompanying text or icon cues.

Mentor tip

Explain color blindness or visual impairment challenges with poor contrast.

(c)(i)

1 mark

In primary memory (RAM) within the server's database process memory space / dynamic cache.

Mentor tip

State primary memory (RAM) or database cache buffer.

(c)(ii)

4 marks

Virtual memory space isolation: The OS assigns independent, private address spaces to distinct user session processes, utilizing hardware memory management units (MMU) to prevent one process from reading or overwriting another process's memory blocks.
Record-level concurrency locking: The database engine and OS enforce transactional locks (mutexes) so that when a customer modifies their profile, that specific record is locked, preventing race conditions or data corruption from simultaneous concurrent writes.

Mentor tip

Explain MMU process memory isolation and database record-level locking mechanisms.

(d)

6 marks

Violation of user trust and informed consent: Customers submitted sensitive personal attributes (date of birth, gender, email address) with the expectation of purchasing goods, not having their personal data commodified and monetized.
Unwanted profiling and harassment: Sharing customer data enables third-party advertisers to build invasive behavioral profiles, subjecting customers to targeted marketing, spam, and potential algorithmic discrimination.
Heightened breach and leak exposure: Transferring data to third parties expands the attack surface, increasing the likelihood of data leaks or credential exploitation beyond the company's direct cybersecurity controls.

Mentor tip

Discuss breach of informed consent, invasive commercial profiling, and third-party data vulnerability risks.

Question 9

15 marks

Student athletic collection membership and sports registration algorithms

Computational thinking, problem-solving and programming

(a)

1 mark

The array SNAMES is not sorted in alphabetical order; binary search strictly requires a pre-sorted dataset to perform interval bisection.

Mentor tip

State that SNAMES is unsorted.

(b)

4 marks

Construct subprogram isIn(X, COL):
1) COL.resetNext() to initialize collection iterator.
2) loop while COL.hasNext():
- ITEM = COL.getNext()
- if ITEM == X then return TRUE
3) end loop.
4) return FALSE.

subprogram isIn (X, COL) COL.resetNext () loop while COL.hasNext () if COL.getNext () = X then return TRUE end if end loop return FALSE end subprogram

Mentor tip

Iterate through the collection; return TRUE upon match, and return FALSE if loop finishes.

(c)

3 marks

Algorithm to count students enrolled in both TENNIS and FOOTBALL:
1) Initialize CONFLICT_COUNT = 0.
2) TENNIS.resetNext().
3) loop while TENNIS.hasNext():
- ID = TENNIS.getNext()
- if isIn(ID, FOOTBALL) then CONFLICT_COUNT = CONFLICT_COUNT + 1
4) Output CONFLICT_COUNT.

CONFLICT_COUNT = 0 TENNIS.resetNext () loop while TENNIS.hasNext () I D = TENNIS.getNext () if isIn (I D, FOOTBALL) then CONFLICT_COUNT = CONFLICT_COUNT + 1 end if end loop output CONFLICT_COUNT

Mentor tip

Iterate through TENNIS collection and call isIn(ID, FOOTBALL) on each ID.

(d)

7 marks

Algorithm to identify students without any chosen sport:
1) Initialize UNREGISTERED_COUNT = 0.
2) loop I from 0 to 99 across all 100 students in SID:
- ID = SID[I]
- HAS_SPORT = isIn(ID, BASKETBALL) or isIn(ID, TENNIS) or isIn(ID, FOOTBALL)
- if not HAS_SPORT then:
* output SNAMES[I]
* UNREGISTERED_COUNT = UNREGISTERED_COUNT + 1
3) After loop terminates:
- if UNREGISTERED_COUNT == 0 then output 'All students have chosen a sport.'

UNREGISTERED_COUNT = 0 loop I from 0 to 99 I D = SID [I] HAS_SPORT = isIn (I D, BASKETBALL) \lor isIn (I D, TENNIS) \lor isIn (I D, FOOTBALL) if not HAS_SPORT then output SNAMES [I] UNREGISTERED_COUNT = UNREGISTERED_COUNT + 1 end if end loop if UNREGISTERED_COUNT = 0 then output "All students have chosen a sport." end if

Mentor tip

Check student ID across all three collections using OR logic; display confirmation message if count remains zero.

Our analysis

Where the marks are

Each part sorted by the topic it mostly tests. Computational thinking, problem-solving and programming carries the most marks on this paper.

Computational thinking, problem-solving and programming23 marks · 33%
Q5, Q7, Q9
System fundamentals17 marks · 24%
Q1, Q3, Q8
Networks17 marks · 24%
Q2, Q7
Computer organisation9 marks · 13%
Q4, Q6, Q8
Resource management4 marks · 6%
Q8

Mentor insights

Traps to watch for

01
Logic precedence in compound Boolean expressions · Q6
Parentheses ensure A XOR B is evaluated first. For (A XOR B) to be 1, A and B must differ. AND NOT C requires C to be 0.
02
Binary search precondition on arrays · Q9
Binary search cannot be performed on an unsorted array. Because SNAMES is unordered, a linear sequential search must be used instead.
03
Resetting collection iterators before traversal · Q9
Before executing a loop while COL.hasNext(), you must call COL.resetNext() to reset the cursor to the beginning of the collection.

Solutions and tips are GeorgeTheTutor's own; the questions are not reproduced here. Not affiliated with or endorsed by the International Baccalaureate Organization.

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Worked solutions

IB Computer Science SL · Paper 1

Computer Science, Standard Level

Session: November 2020
Marks: 70
Duration: 1 hour 30 min
Calculator: Not allowed
Questions: 9

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Keep your copy of the paper open alongside. We don't reproduce the questions: each part below is labelled to match the November 2020 global paper, which your school or the IB can provide.

Practice mode

Hide our working until you've had a go.

Questions 1–6 · 25 marks

Question 1

3 marks

Word processor typing productivity and purpose of technical documentation

System fundamentals

(a)

2 marks

Mentor tip

Identify mail merge, autocorrect / text macros, or boilerplate templates.

(b)

1 mark

Mentor tip

State software maintenance, configuration, and troubleshooting for technical personnel.

Question 2

6 marks

Client-server architecture in airport check-in kiosks

Networks

(a)(i)

1 mark

A hardware terminal or software application that requests data, validation, or services from a central server across a network.

Mentor tip

State that a client initiates service requests to a central server.

(a)(ii)

1 mark

A centralized high-performance computer or software process that listens for client requests, manages centralized resources, and returns requested data or services.

Mentor tip

State that a server manages shared resources and services client requests.

(b)

4 marks

Flight database management: Queries flight manifests and passenger records to verify bookings and passport numbers sent from kiosks.
Real-time seat assignment concurrency: Updates seating charts and reserves chosen seats, enforcing transaction locks to prevent double-booking across simultaneous kiosk check-ins.
Boarding pass payload generation: Validates check-in completion and transmits digitized boarding pass data and barcode tokens back to the kiosk printer.

Mentor tip

Explain validating passenger credentials, preventing seat double-booking, and issuing boarding authorization.

Question 3

4 marks

Comparison of direct changeover and parallel running implementation

System fundamentals

4 marks

Direct Changeover:
- Process: The legacy system is decommissioned completely at a set date/time, and the new system takes over all operational responsibilities immediately.
- Trade-off: Incurs the lowest operating costs with zero duplication of effort, but presents catastrophic operational risk if unforeseen critical defects halt production.
Parallel Running:
- Process: Both legacy and new systems operate concurrently for a trial period, processing identical transaction data.
- Trade-off: Guarantees business continuity and provides a safe fallback if the new system fails, but doubles staffing workload and infrastructure operating expenses.

Mentor tip

Contrast operational risk and running expense across both methods.

Question 4

4 marks

CPU machine instruction cycle registers and decoding

Computer organisation

(a)

1 mark

The program is held in primary memory (RAM) while executing.

Mentor tip

State primary memory (RAM).

(b)

1 mark

The Control Unit (CU) of the central processing unit.

Mentor tip

State the Control Unit.

(c)

2 marks

Stores the memory address of the next instruction or data word to be fetched from or written to primary memory (RAM), driving the system address bus.

Mentor tip

Explain holding the target memory address for the address bus.

Question 5

4 marks

Bubble sort algorithm operational mechanics

Computational thinking, problem-solving and programming

4 marks

1) Pass initialization: The algorithm performs multiple sequential passes through the array elements.
2) Pairwise comparison: On each pass, it compares adjacent elements (e.g. A[I] and A[I + 1]).
3) Conditional swap: If the adjacent pair is in the wrong order (e.g. A[I] > A[I + 1] for ascending sort), their values are swapped using an auxiliary temporary variable.
4) Termination: Passes repeat, with the unsorted portion shrinking by one each pass, until a complete pass occurs with zero swaps, confirming the array is sorted.

Mentor tip

Detail sequential passes, adjacent element comparisons, conditional swapping, and termination upon zero swaps.

Question 6

4 marks

Truth table evaluation for composite Boolean expression (A xor B) and not C

Computer organisation

4 marks

Expression: (A XOR B) AND (NOT C)
Inputs A, B, C across all 8 truth table rows:
- A=0, B=0, C=0 -> (0 XOR 0) = 0, NOT 0 = 1 -> 0 AND 1 = 0
- A=0, B=0, C=1 -> (0 XOR 0) = 0, NOT 1 = 0 -> 0 AND 0 = 0
- A=0, B=1, C=0 -> (0 XOR 1) = 1, NOT 0 = 1 -> 1 AND 1 = 1
- A=0, B=1, C=1 -> (0 XOR 1) = 1, NOT 1 = 0 -> 1 AND 0 = 0
- A=1, B=0, C=0 -> (1 XOR 0) = 1, NOT 0 = 1 -> 1 AND 1 = 1
- A=1, B=0, C=1 -> (1 XOR 0) = 1, NOT 1 = 0 -> 1 AND 0 = 0
- A=1, B=1, C=0 -> (1 XOR 1) = 0, NOT 0 = 1 -> 0 AND 1 = 0
- A=1, B=1, C=1 -> (1 XOR 1) = 0, NOT 1 = 0 -> 0 AND 0 = 0
Notice the expression evaluates to 1 strictly for input rows 010 and 100.

(A \oplus B) \land \neg C = 1 ⟺ (A \neq = B) \land (C = 0)

Mentor tip

Compute intermediate terms (A XOR B) and (NOT C) in separate columns before performing the logical AND.

Questions 7–9 · 45 marks

Question 7

15 marks

School LAN infrastructure, router role, throughput bottlenecks, and inventory algorithm

Networks
Computational thinking, problem-solving and programming

(a)

3 marks

Network boundary routing: Connects the internal school LAN to the external public Internet wide area network.
Packet forwarding by IP routing: Examines destination IP addresses on incoming data packets and consults routing tables to forward packets along the optimal physical path.
NAT and gateway services: Translates internal private IPv4 addresses into a public IP address (Network Address Translation) and filters unauthorized incoming traffic.

Mentor tip

Explain connecting LAN to WAN, packet forwarding via routing tables, and NAT translation.

(b)

4 marks

1) Network bandwidth saturation during peak periods: Simultaneous high-volume streaming, cloud software updates, or file downloads by hundreds of students and faculty exceed total available ISP uplink bandwidth.
2) Collisions and wireless channel congestion: Intense Wi-Fi traffic on overlapping radio channels creates packet collisions and signal interference, requiring frequent packet retransmissions.

Mentor tip

Identify peak bandwidth saturation and wireless radio channel interference.

(c)

4 marks

1) State-of-the-art perimeter firewall: Configured with strict packet filtering rules to block unauthorized inbound connection attempts and close vulnerable network ports.
2) Network segmentation with Virtual LANs (VLANs): Isolating sensitive administrative and student record servers on a restricted subnet segregated from student BYOD Wi-Fi traffic.

Mentor tip

Detail firewall access policies and VLAN network isolation.

(d)

4 marks

Algorithm steps to determine items needing replenishment:
1) Open and read the supplies inventory file sequentially until end of file.
2) For each supply record, extract ID, NAME, MAX_QTY, MIN_QTY, and REMAINING_QTY.
3) Evaluate condition: if REMAINING_QTY <= MIN_QTY then:
- Calculate order amount: ORDER_QTY = MAX_QTY - REMAINING_QTY.
- Output ID, NAME, and ORDER_QTY.
4) Close file after all records have been evaluated.

If REMAINING \leq MIN ⟹ ORDER_QTY = MAX - REMAINING

Mentor tip

Check if remaining quantity is at or below minimum, then compute the difference to maximum.

Question 8

15 marks

Website usability, concurrency security in OS, and customer data ethics

System fundamentals
Computer organisation
Resource management

(a)

2 marks

Navigation intuitiveness: Clear, hierarchical menu structure, consistent breadcrumb trails, and effective search functionality.
Visual readability and accessibility: Legible font sizes, strong color contrast between text and background, and responsive layout scaling across mobile and desktop devices.

Mentor tip

Identify navigation structure and visual readability / accessibility contrast.

(b)

2 marks

Mentor tip

Explain color blindness or visual impairment challenges with poor contrast.

(c)(i)

1 mark

In primary memory (RAM) within the server's database process memory space / dynamic cache.

Mentor tip

State primary memory (RAM) or database cache buffer.

(c)(ii)

4 marks

Virtual memory space isolation: The OS assigns independent, private address spaces to distinct user session processes, utilizing hardware memory management units (MMU) to prevent one process from reading or overwriting another process's memory blocks.
Record-level concurrency locking: The database engine and OS enforce transactional locks (mutexes) so that when a customer modifies their profile, that specific record is locked, preventing race conditions or data corruption from simultaneous concurrent writes.

Mentor tip

Explain MMU process memory isolation and database record-level locking mechanisms.

(d)

6 marks

Violation of user trust and informed consent: Customers submitted sensitive personal attributes (date of birth, gender, email address) with the expectation of purchasing goods, not having their personal data commodified and monetized.
Unwanted profiling and harassment: Sharing customer data enables third-party advertisers to build invasive behavioral profiles, subjecting customers to targeted marketing, spam, and potential algorithmic discrimination.
Heightened breach and leak exposure: Transferring data to third parties expands the attack surface, increasing the likelihood of data leaks or credential exploitation beyond the company's direct cybersecurity controls.

Mentor tip

Discuss breach of informed consent, invasive commercial profiling, and third-party data vulnerability risks.

Question 9

15 marks

Student athletic collection membership and sports registration algorithms

Computational thinking, problem-solving and programming

(a)

1 mark

The array SNAMES is not sorted in alphabetical order; binary search strictly requires a pre-sorted dataset to perform interval bisection.

Mentor tip

State that SNAMES is unsorted.

(b)

4 marks

Construct subprogram isIn(X, COL):
1) COL.resetNext() to initialize collection iterator.
2) loop while COL.hasNext():
- ITEM = COL.getNext()
- if ITEM == X then return TRUE
3) end loop.
4) return FALSE.

subprogram isIn (X, COL) COL.resetNext () loop while COL.hasNext () if COL.getNext () = X then return TRUE end if end loop return FALSE end subprogram

Mentor tip

Iterate through the collection; return TRUE upon match, and return FALSE if loop finishes.

(c)

3 marks

Algorithm to count students enrolled in both TENNIS and FOOTBALL:
1) Initialize CONFLICT_COUNT = 0.
2) TENNIS.resetNext().
3) loop while TENNIS.hasNext():
- ID = TENNIS.getNext()
- if isIn(ID, FOOTBALL) then CONFLICT_COUNT = CONFLICT_COUNT + 1
4) Output CONFLICT_COUNT.

CONFLICT_COUNT = 0 TENNIS.resetNext () loop while TENNIS.hasNext () I D = TENNIS.getNext () if isIn (I D, FOOTBALL) then CONFLICT_COUNT = CONFLICT_COUNT + 1 end if end loop output CONFLICT_COUNT

Mentor tip

Iterate through TENNIS collection and call isIn(ID, FOOTBALL) on each ID.

(d)

7 marks

Algorithm to identify students without any chosen sport:
1) Initialize UNREGISTERED_COUNT = 0.
2) loop I from 0 to 99 across all 100 students in SID:
- ID = SID[I]
- HAS_SPORT = isIn(ID, BASKETBALL) or isIn(ID, TENNIS) or isIn(ID, FOOTBALL)
- if not HAS_SPORT then:
* output SNAMES[I]
* UNREGISTERED_COUNT = UNREGISTERED_COUNT + 1
3) After loop terminates:
- if UNREGISTERED_COUNT == 0 then output 'All students have chosen a sport.'

UNREGISTERED_COUNT = 0 loop I from 0 to 99 I D = SID [I] HAS_SPORT = isIn (I D, BASKETBALL) \lor isIn (I D, TENNIS) \lor isIn (I D, FOOTBALL) if not HAS_SPORT then output SNAMES [I] UNREGISTERED_COUNT = UNREGISTERED_COUNT + 1 end if end loop if UNREGISTERED_COUNT = 0 then output "All students have chosen a sport." end if

Mentor tip

Check student ID across all three collections using OR logic; display confirmation message if count remains zero.

Our analysis

Where the marks are

Each part sorted by the topic it mostly tests. Computational thinking, problem-solving and programming carries the most marks on this paper.

Computational thinking, problem-solving and programming23 marks · 33%
Q5, Q7, Q9
System fundamentals17 marks · 24%
Q1, Q3, Q8
Networks17 marks · 24%
Q2, Q7
Computer organisation9 marks · 13%
Q4, Q6, Q8
Resource management4 marks · 6%
Q8

Mentor insights

Traps to watch for

01
Logic precedence in compound Boolean expressions · Q6
Parentheses ensure A XOR B is evaluated first. For (A XOR B) to be 1, A and B must differ. AND NOT C requires C to be 0.
02
Binary search precondition on arrays · Q9
Binary search cannot be performed on an unsorted array. Because SNAMES is unordered, a linear sequential search must be used instead.
03
Resetting collection iterators before traversal · Q9
Before executing a loop while COL.hasNext(), you must call COL.resetNext() to reset the cursor to the beginning of the collection.

Solutions and tips are GeorgeTheTutor's own; the questions are not reproduced here. Not affiliated with or endorsed by the International Baccalaureate Organization.

Want someone to go through your paper with you?

Our maths mentors took these exams recently. One-to-one, they'll find where your marks are going and fix it before May.

Find your maths mentor More past papers