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Worked solutions

IB Computer Science HL · Paper 1

Computer Science, Higher Level

Session: May 2016
Marks: 100
Duration: 2 hours 10 min
Calculator: Not allowed
Questions: 15

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12 Q13 Q14 Q15

Keep your copy of the paper open alongside. We don't reproduce the questions: each part below is labelled to match the May 2016 global paper, which your school or the IB can provide.

Practice mode

Hide our working until you've had a go.

Questions 1–10 · 25 marks

Question 1

2 marks

Maintenance challenges of legacy systems

System fundamentals

(a)

2 marks

Define a legacy system as an outdated computing infrastructure or obsolete software architecture that remains critical to organizational operations.
Explain one maintenance problem: modifying or patching legacy code is exceptionally difficult and costly due to missing, out-of-date documentation, disorganized source code (spaghetti code), and a scarcity of programmers proficient in obsolete programming languages.

Mentor tip

Clarify that legacy systems use outdated technology and explicitly link to missing documentation or scarce programming expertise.

Question 2

2 marks

Role and mechanism of a failover system

System fundamentals

(a)

2 marks

Identify that a failover system maintains a redundant, standby secondary server or system constantly synchronized with the primary platform.
Describe how it operates: when a hardware fault, power disruption, or software crash disables the primary system, the failover mechanism seamlessly switches operations to the secondary system automatically, avoiding disruption to end users.

Mentor tip

Emphasize automatic takeover by a redundant standby system during primary failure to preserve availability.

Question 3

2 marks

Role of the Control Unit (CU) in the CPU

Computer organisation

(a)

2 marks

State the primary function of the Control Unit: fetching instructions from main memory (RAM) and decoding them into micro-operations and control signals.
Outline its coordination role: directing the timing and movement of data between CPU registers, the Arithmetic Logic Unit (ALU), and input/output interfaces across the control bus.

Mentor tip

Focus on instruction fetching/decoding and issuing synchronization control signals to CPU components.

Question 4

3 marks

Truth table construction for A XOR (B OR C)

Computer organisation

(a)

3 marks

Evaluate the sub-expression (B OR C) for all 8 input combinations of binary inputs A, B, and C.
Apply the exclusive-OR (XOR) operator between input A and the intermediate result (B OR C), outputting 1 if and only if exactly one operand is true:
Row 1: A=0, B=0, C=0 -> B OR C = 0 -> 0 XOR 0 = 0
Row 2: A=0, B=0, C=1 -> B OR C = 1 -> 0 XOR 1 = 1
Row 3: A=0, B=1, C=0 -> B OR C = 1 -> 0 XOR 1 = 1
Row 4: A=0, B=1, C=1 -> B OR C = 1 -> 0 XOR 1 = 1
Row 5: A=1, B=0, C=0 -> B OR C = 0 -> 1 XOR 0 = 1
Row 6: A=1, B=0, C=1 -> B OR C = 1 -> 1 XOR 1 = 0
Row 7: A=1, B=1, C=0 -> B OR C = 1 -> 1 XOR 1 = 0
Row 8: A=1, B=1, C=1 -> B OR C = 1 -> 1 XOR 1 = 0

A 00001111 B 00110011 C 01010101 B \lor C 01110111 A \oplus (B \lor C) 01111000

Mentor tip

Evaluate (B OR C) first as an intermediate column before applying the XOR operation with A.

Question 5

2 marks

Hexadecimal 3B representation in an 8-bit register

Computer organisation

(a)

2 marks

Convert hexadecimal digit 3 into 4-bit binary: 3_{16} = 0011_2.
Convert hexadecimal digit B (decimal 11) into 4-bit binary: B_{16} = 1011_2.
Concatenate the two 4-bit nibbles into an 8-bit byte: 00111011.

3 B_{16} = (00111011)_{2}

Mentor tip

Convert each hex character into its 4-bit nibble and ensure all 8 bits including leading zeros are present.

Question 6

1 mark

Two iterations of ascending bubble sort

Computational thinking, problem-solving and programming

(a)

1 mark

Initial array: [9, 11, 3, 4, 5, 7, 1, 2].
Pass 1 (left-to-right adjacent comparisons and swaps):
Compare 9 and 11: no swap [9, 11, ...]. Compare 11 and 3: swap -> [9, 3, 11, ...]. Compare 11 and 4: swap -> [9, 3, 4, 11, ...]. Compare 11 and 5: swap -> [9, 3, 4, 5, 11, ...]. Compare 11 and 7: swap -> [9, 3, 4, 5, 7, 11, ...]. Compare 11 and 1: swap -> [9, 3, 4, 5, 7, 1, 11, ...]. Compare 11 and 2: swap -> [9, 3, 4, 5, 7, 1, 2, 11]. Largest element 11 is placed in final index.
Pass 2: Compare 9 and 3: swap -> [3, 9, 4, 5, 7, 1, 2, 11]. Compare 9 and 4: swap -> [3, 4, 9, 5, 7, 1, 2, 11]. Compare 9 and 5: swap -> [3, 4, 5, 9, 7, 1, 2, 11]. Compare 9 and 7: swap -> [3, 4, 5, 7, 9, 1, 2, 11]. Compare 9 and 1: swap -> [3, 4, 5, 7, 1, 9, 2, 11]. Compare 9 and 2: swap -> [3, 4, 5, 7, 1, 2, 9, 11].
Result after two complete iterations: 3, 4, 5, 7, 1, 2, 9, 11.

Mentor tip

In ascending bubble sort, each pass bubbles the next largest remaining value to the right.

Question 7

3 marks

Virtual machines as abstraction for multi-platform software testing

Resource management

(a)

3 marks

Explain virtual machine abstraction: A virtual machine creates an emulated, self-contained software representation of physical hardware and target operating systems, abstracting away the specific underlying host computer architecture.
Explain why this aids multi-platform testing: Developers can run multiple distinct guest operating systems (e.g., Linux, Windows, macOS) simultaneously on a single host computer, without purchasing multiple distinct physical machines.
Describe execution independence: Intermediate bytecode or target binaries run inside the standardized VM environment, which translates or interprets instructions to host CPU calls, ensuring consistent behavior across diverse deployment targets.

Mentor tip

Emphasize software emulation that abstracts host hardware, allowing multi-OS testing on a single physical machine.

Question 8

3 marks

Resource allocation in collaborative Voice over IP (VoIP)

Networks

(a)

3 marks

Outline how VoIP functions in nationwide office collaboration: Voice and video streams are digitized, packetized, and transmitted across IP data networks instead of dedicated public switched telephone circuits, enabling unified communications (video conferencing, desktop sharing, presence indicators).
Explain bandwidth resource management: Video and audio streaming require continuous, predictable network bandwidth. Without Quality of Service (QoS) bandwidth reservation, high traffic loads cause packet jitter, latency, and packet loss, disrupting real-time meetings.
Discuss routing and network segregation: Routers must prioritize voice packets ahead of bulk web traffic or downloads, or route VoIP over dedicated virtual local area networks (VLANs) to prevent internal congestion from degrading call clarity.

Mentor tip

Address both the communication method (packetized audio/video) and specific resource constraints such as bandwidth and router QoS.

Question 9

4 marks

Operating system multitasking functions

Resource management

(a)

4 marks

Function 1 - Processor Management (CPU Scheduling): The operating system schedules CPU time slices across active processes using round-robin or priority preemptive scheduling algorithms, giving users the perception of simultaneous program execution.
Detail process isolation and context switching: The scheduler manages interrupts, saves register contents, and switches process states (Ready, Running, Blocked) cleanly without race conditions.
Function 2 - Memory Management: The operating system allocates distinct memory partitions or address spaces to each concurrent process to prevent unauthorized memory overwriting between applications.
Detail virtual memory handling: If multiple executing programs exceed physical RAM capacity, the OS manages paging to secondary storage swap space to sustain multitasking without application crashes.

Mentor tip

Select processor scheduling and memory allocation as the two key OS functions, elaborating on time slicing and process memory isolation.

Question 10

3 marks

Ethical considerations of workplace CCTV surveillance

System fundamentals

(a)

3 marks

State the organizational rationale vs privacy tension: Employers have a legitimate interest in safeguarding physical premises, company assets, and employee safety, but this must balance against the fundamental privacy rights and mental well-being of staff.
Provide an example of surveillance misuse: Constant, invasive camera monitoring of individual worker movements, social interactions, or productivity micro-behaviors can generate an atmosphere of distrust, harassment, or intimidation.
Explain preventive policies and controls: Management must establish clear, transparent surveillance policies defining camera locations (strictly prohibiting private spaces like restrooms), specifying retention periods, restricting video access to vetted security personnel, and barring unauthorized managerial use.

Mentor tip

Structure the discussion with the balance of rights, a concrete risk of surveillance abuse, and explicit organizational safeguards.

Questions 11–15 · 75 marks

Question 11

15 marks

University examination record system upgrade

System fundamentals

(a)

2 marks

Identify aspect 1: Access permissions and security control — establishing strict authorization hierarchies (e.g., student read-only access for personal transcripts vs exam officer administrative write access).
Identify aspect 2: Data volume, archiving schedules, and storage scalability — accommodating rapid record expansion for current students while archiving two-year-old student papers and preserving historical numerical grades.

Mentor tip

Highlight access privileges and data volume/frequency of access between current and past student records.

(b)

3 marks

Explain direct observation: Analysts directly shadow office staff as they interact with the existing system during everyday administrative routines.
Detail benefits of first-hand insight: It reveals practical workflows, data bottlenecks, user operational errors, and actual usage patterns that staff might overlook or underreport in questionnaires.
Explain how this shapes requirements: Direct qualitative evidence exposes unstated pain points, ensuring the proposed system retains effective current features while rectifying inefficiency and validation flaws.

Mentor tip

Direct observation provides unbiased, first-hand evidence of real user workflows and systemic bottlenecks.

(c)

3 marks

State the purpose of creating a prototype: Presenting a functional early model to the examination office to validate core workflows, forms, and user interfaces before full-scale coding begins.
Explain feedback and iterative refinement: Allowing administrative staff to test navigation, identify missing requirements, and suggest adjustments early, significantly lowering redesign costs.
Accelerate consensus and development: Ensuring technical developers and end-user stakeholders share an identical understanding of system specifications before committing resources.

Mentor tip

Explain that prototypes elicit early user feedback, clarify functional requirements, and prevent costly late-stage revisions.

(d)

4 marks

Problem 1 - Data loss and corruption during transfer: Moving extensive exam records and student grades across network protocols or storage drives introduces risks of incomplete transmissions, corrupted fields, or packet drops, leaving academic records truncated or invalid.
Discussion 1: Resolving data corruption requires robust validation algorithms (such as hash checksum verification), pre-migration database backups, and data integrity audits before decommissioning legacy databases.
Problem 2 - Incompatibility of database formats and data structures: Legacy databases may use obsolete field encodings, deprecated data types, or proprietary schemas that do not map directly into the modern database schema.
Discussion 2: Resolving format mismatches requires writing and thoroughly testing Extraction, Transformation, and Loading (ETL) scripts, which can lead to project delays and elevated implementation costs if exceptions occur.

Mentor tip

Name data loss/corruption and schema/format incompatibility, discussing consequences and validation requirements for each.

(e)

3 marks

Outline the economic cost of parallel running: The organization must finance duplicate infrastructure, running both old servers and new hardware concurrently.
Explain staffing and operational expenses: Staff must enter all grades and examination records twice into both systems to verify parity, demanding substantial overtime wages or temporary staffing.
Discuss risk mitigation value: Although operationally expensive, this investment eliminates the catastrophic economic liability of complete university data loss or operational shutdown should the new system fail unexpectedly.

Mentor tip

Focus on duplicate operational costs (staffing, power, dual entry) balanced against catastrophic failure insurance.

Question 12

15 marks

College campus network and access policies

Networks

(a)

4 marks

Explain reliability of wireless transmission: Wi-Fi signals fluctuate based on physical distance from the access point, attenuation through building walls, electromagnetic interference from surrounding electronic appliances, and radio channel saturation when many students connect simultaneously.
Explain reliability of Ethernet transmission: Wired connections provide consistent, dedicated bandwidth with physical shielding inside twisted-pair cabling, making data transmission stable and immune to external radio interference.
Compare physical vulnerability: Ethernet links remain reliably connected provided cables and physical RJ-45 ports remain undamaged, whereas Wi-Fi experiences intermittent signal drops due to dynamic environmental interference.

Mentor tip

Contrast Wi-Fi susceptibility to radio interference, wall attenuation, and user density with the shielded stability of wired Ethernet.

(b)

4 marks

Feature 1 - Strong End-to-End Encryption: All payload packets traveling through the public internet are encrypted using symmetric ciphers (e.g., AES) so that any packet intercepted by a third party remains indecipherable.
Feature 2 - Tunneling and Encapsulation: VPN protocols (e.g., IPsec, OpenVPN) encapsulate entire original packets inside new IP headers with secure outer routing, concealing internal college IP addresses and packet metadata from eavesdroppers.
Feature 3 - Mutual Authentication: Both the client and the campus VPN gateway must authenticate using credentials, multi-factor tokens, or digital certificates before an authorized communication tunnel is established.

Mentor tip

Select encryption and tunneling/authentication as the two security features, explaining how each prevents unauthorized inspection.

(c)

1 mark

Identify one essential security protocol technology for VPN implementation: IPsec (Internet Protocol Security), TLS (Transport Layer Security), or SSL (Secure Sockets Layer).

Mentor tip

State a recognized tunneling/security protocol such as IPsec, TLS, or SSL.

(d)

6 marks

Advantage 1: Universal device synchronization and collaboration — cloud platforms allow students to co-edit shared project documents simultaneously across personal smartphones, home PCs, and college laptops without manual file copying.
Advantage 2: Modern feature availability and zero maintenance — commercial web services update continuously with advanced toolsets and abundant cloud storage exceeding what the college internal IT department can provision.
Disadvantage 1: Data sovereignty, security, and confidentiality risks — uploading sensitive research, student projects, or personal identification to third-party cloud servers exposes student data to external platform data breaches or unclear intellectual property terms.
Disadvantage 2: Academic misconduct and compliance issues — public blogs and unmonitored external platforms can facilitate plagiarism, defamatory postings, or cyberbullying outside the moderation and safeguarding purview of college IT policy.

Mentor tip

Balance collaborative flexibility and ubiquitous access against institutional compliance, data ownership, and moderation challenges.

Question 13

15 marks

Automated car park ticketing and tariff management

Abstract data structures
Resource management
Computational thinking, problem-solving and programming

(a)

2 marks

Explain dynamic memory allocation: The number of vehicles in the car park fluctuates constantly throughout the day; a linked list dynamically allocates and deallocates memory node-by-node without needing a pre-allocated fixed-capacity array.
Explain efficient node insertion: New ticket records can be appended or linked in constant time O(1) as cars arrive without needing to shift contiguous memory blocks.

Mentor tip

Link dynamic sizing and efficient runtime insertion to the unpredictable number of cars entering the facility.

(b)

2 marks

Part (i) - Concurrent processes: Raising the entrance barrier and raising the exit barrier simultaneously, or a customer paying at an automatic payment kiosk while the entrance barrier is being raised for an incoming vehicle.
Part (ii) - Non-concurrent processes: Updating the central available spaces display counter simultaneously by an entry process (decrementing) and an exit process (incrementing) without mutual exclusion, or simultaneously modifying the pointers of the shared linked list.

Mentor tip

Physical barrier movements on separate gates can happen concurrently; modifying shared counters or list pointers concurrently causes race conditions.

(c)

1 mark

Identify the validation check: The exit terminal must verify that the ticket has been paid and that the elapsed time between payment and exit does not exceed the allowed threshold of 10 minutes:
Condition: (CurrentTime - PaidAt <= 10) AND (PaidOn == CurrentDate).

Elapsed Minutes = CurrentTime - PaidAt \leq 10

Mentor tip

State that elapsed time since payment must be within the 10-minute departure window.

(d)

3 marks

Step 1 - Process the leaving vehicle first at the exit: Check exit ticket -> raise exit barrier -> increment car park display counter (spaces available increases).
Step 2 - Prioritizing exit prevents deadlocks: By registering the newly freed space before admitting an incoming car, the display reflects accurate capacity.
Step 3 - Process incoming vehicle at the entrance: Check display > 0 -> issue entry ticket -> decrement car park display counter -> raise entrance barrier.

Mentor tip

Show that the exit sequence precedes the entry sequence so the display counter increments before decrementing, preventing false full-capacity lockouts.

(e)

2 marks

Identify memory implication: Leaving paid and exited ticket objects in the linked list causes the data structure to grow indefinitely, consuming increasing amounts of RAM over time.
Identify search latency implication: Linear sequential searching across an ever-growing linked list degrades ticket lookup efficiency from O(k) for active cars to O(N) over historical records, slowing barrier response times.

Mentor tip

Explain that failing to remove historical records causes memory bloat and degrades sequential search latency.

(f)

5 marks

Calculate the date difference between arrival date (AD) and payment date (PD).
If the stay spans across dates (PD != AD):
Compute excess days: XD = PD - AD. Apply overnight daily cap: Total = XD * 60.00 EUR (or XD * 30.00 EUR per day). For consecutive days as specified in the rules, stay across two consecutive days costs 60.00 EUR.
Else (stay is within the same calendar day), compute parking duration DRN in minutes from arrival time to payment time:
Case 1: DRN <= 30 -> Fee = RULES[0][0] = 0.50 EUR.
Case 2: 30 < DRN <= 120 -> Fee = RULES[0][1] = 3.00 EUR.
Case 3: 120 < DRN <= 150 -> Fee = RULES[0][1] + RULES[1][0] = 3.00 + 5.00 = 8.00 EUR.
Case 4: 150 < DRN <= 240 -> Fee = RULES[0][1] + RULES[1][1] = 3.00 + 15.00 = 18.00 EUR.
Case 5: DRN > 240 -> Fee = RULES[1][2] = 30.00 EUR.
Output the calculated total fee.

Fee = ⎩ ⎨ ⎧ 60.00 0.50 3.00 8.00 18.00 30.00 if PaidDate > ArrivalDate if DRN \leq 30 if 30 < DRN \leq 120 if 120 < DRN \leq 150 if 150 < DRN \leq 240 if DRN > 240

Mentor tip

Check multi-day stays first before evaluating same-day duration brackets against the RULES table.

Question 14

15 marks

Mobile app restaurant location and review analytics

Computational thinking, problem-solving and programming
Control systems
Abstract data structures
System fundamentals

(a)

1 mark

Locate Zone [2] in the RESULTS table (the zone furthest from the user).
Sum all restaurants across the three price categories for Zone [2]: 2 + 3 + 1 = 6 restaurants.

2 + 3 + 1 = 6

Mentor tip

Sum the row values across Zone [2] in the RESULTS matrix: 2 + 3 + 1 = 6.

(b)

4 marks

Step 1 - GPS Trilateration: The smartphone GPS receiver captures atomic time-stamped radio signals from at least 3 (preferably 4) orbital GPS satellites, solving geometric sphere equations to determine exact user coordinates (latitude, longitude).
Step 2 - Map coordinate projection: The smartphone application plots the user coordinate at the center of the local geographic map scaled to current screen zoom levels.
Step 3 - Concentric zone calculation: The app computes Euclidean or Haversine distance radii from the center coordinate.
Step 4 - Display rendering: The system renders concentric boundary circles for Zone 0, Zone 1, and Zone 2 around the user position on the digital map overlay.

Mentor tip

Detail trilateration from satellite signals to establish user coordinates, followed by drawing radial concentric circles on the map.

(c)

5 marks

Initialize tracking variables: MAX_LIKES = -1, BEST_RESTAURANT = "".
Traverse collection LIKES sequentially while LIKES.hasNext():
Read four consecutive items per restaurant: ZONE = LIKES.getNext(), NUM_LIKES = LIKES.getNext(), NAME = LIKES.getNext(), RATING = LIKES.getNext().
Check if ZONE == 1: if true and NUM_LIKES > MAX_LIKES, update MAX_LIKES = NUM_LIKES and BEST_RESTAURANT = NAME.
After completing traversal across the collection, output BEST_RESTAURANT.

Mentor tip

Step through the collection four elements per entity (zone, likes, name, rating) and maintain the maximum likes for Zone 1.

(d)

3 marks

Construct three separate binary search trees (BST_0, BST_1, BST_2), one dedicated to each distance zone.
Populate BSTs from LIKES: Parse the collection in 4-tuples; use the zone identifier to route the entry to the corresponding tree, inserting a node with key = NUM_LIKES and value = restaurant data (inserting smaller keys in left subtree, larger keys in right subtree).
Traverse each tree in-order (or reverse in-order for descending popularity) to generate an ordered list for each zone, then concatenate the three lists in sequence: Zone 0, then Zone 1, then Zone 2.

Mentor tip

Build one binary search tree per zone keyed on likes, then perform in-order traversals and concatenate the resulting lists.

(e)

2 marks

Identify disadvantage: Online customer reviews can be biased, malicious, or fabricated.
Elaborate on business impact: Competitors or disgruntled individuals can post fake negative reviews, while reputation marketing firms create artificial positive ratings, distorting authentic consumer perception and damaging restaurant revenue without fair recourse.

Mentor tip

Explain that online review systems are vulnerable to fake or unverified feedback that unfairly distorts business reputation.

Question 15

15 marks

Fibonacci recursion tracing and iterative optimization

Computational thinking, problem-solving and programming
Abstract data structures

(a)

1 mark

Generate Fibonacci sequence terms starting from F_0 = 0, F_1 = 1:
F_0=0, F_1=1, F_2=1, F_3=2, F_4=3, F_5=5, F_6=8, F_7=13, F_8=21.
The 8th term is 21.

F_{8} = 21

Mentor tip

Ensure index matching starting at F_0 = 0 up to F_8 = 21.

(b)

3 marks

Trace recursive calls for fibo(4):
Level 1: fibo(4) = fibo(3) + fibo(2)
Level 2: fibo(3) expands to fibo(2) + fibo(1); fibo(2) expands to fibo(1) + fibo(0)
Level 3: Left fibo(2) expands to fibo(1) + fibo(0)
Substitute base cases: fibo(1) = 1, fibo(0) = 0:
Left subtree: fibo(3) = (1 + 0) + 1 = 2
Right subtree: fibo(2) = 1 + 0 = 1
Final summation: fibo(4) = 2 + 1 = 3.

fibo (4) = fibo (3) + fibo (2) = (fibo (2) + fibo (1)) + (fibo (1) + fibo (0)) = ((fibo (1) + fibo (0)) + 1) + (1 + 0) = ((1 + 0) + 1) + 1 = 3

Mentor tip

Show the full expansion tree down to base cases fibo(1)=1 and fibo(0)=0 before summing up to 3.

(c)

6 marks

Construct iterative algorithm to calculate the Nth Fibonacci number in O(N) time and O(1) space:
Pseudocode:
fiboIterative(N)
if N == 0 then return 0
if N == 1 then return 1
PREV2 = 0
PREV1 = 1
CURRENT = 0
loop I from 2 to N
CURRENT = PREV1 + PREV2
PREV2 = PREV1
PREV1 = CURRENT
end loop
return CURRENT
end fiboIterative

Mentor tip

Handle base cases 0 and 1, initialize two tracking variables, loop from 2 to N, and update variables iteratively.

(d)

3 marks

Construct procedure to output the first N terms of the Fibonacci sequence using fibo():
outputFirstN(N)
loop I from 0 to N - 1
output(fibo(I))
end loop
end outputFirstN
Each iteration calls fibo(I) and outputs the generated term.

Mentor tip

Set up a loop from index 0 to N-1, calling fibo(I) and outputting the result in sequence.

(e)

2 marks

Explain call stack push: Each time a recursive function call occurs, a new stack activation frame containing local variables, parameters, and the return address is pushed onto the system call stack.
Explain call stack pop: When a base case is reached, the function completes execution, returning its computed value and popping the activation frame off the stack to resume execution in the calling routine.

Mentor tip

Describe pushing activation frames (return address and local variables) on invocation, and popping frames upon return.

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 programming26 marks · 26%
Q6, Q13, Q14, Q15
System fundamentals24 marks · 24%
Q1, Q2, Q10, Q11, Q14
Networks18 marks · 18%
Q8, Q12
Resource management12 marks · 12%
Q7, Q9, Q13
Abstract data structures9 marks · 9%
Q13, Q14, Q15
Computer organisation7 marks · 7%
Q3, Q4, Q5
Control systems4 marks · 4%
Q14

Mentor insights

Traps to watch for

01
Boolean operator precedence in A XOR (B OR C) · Q4
The OR expression inside parentheses must be evaluated first. Only rows where A and (B OR C) differ in truth value produce an output of 1.
02
Car park ticket linked list accumulation · Q13
Leaving paid tickets in the linked list degrades lookup times from O(1) or O(active) to O(N) linear scans across all historic entries, and risks memory exhaustion.
03
Exponential call overhead in naive recursive Fibonacci · Q15
Tracing fibo(4) requires 9 total function calls due to repeated recalculation of identical subproblems (fibo(2) is calculated twice), demonstrating why dynamic programming or iteration is superior.

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 HL · Paper 1

Computer Science, Higher Level

Session: May 2016
Marks: 100
Duration: 2 hours 10 min
Calculator: Not allowed
Questions: 15

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12 Q13 Q14 Q15

Keep your copy of the paper open alongside. We don't reproduce the questions: each part below is labelled to match the May 2016 global paper, which your school or the IB can provide.

Practice mode

Hide our working until you've had a go.

Questions 1–10 · 25 marks

Question 1

2 marks

Maintenance challenges of legacy systems

System fundamentals

(a)

2 marks

Define a legacy system as an outdated computing infrastructure or obsolete software architecture that remains critical to organizational operations.
Explain one maintenance problem: modifying or patching legacy code is exceptionally difficult and costly due to missing, out-of-date documentation, disorganized source code (spaghetti code), and a scarcity of programmers proficient in obsolete programming languages.

Mentor tip

Clarify that legacy systems use outdated technology and explicitly link to missing documentation or scarce programming expertise.

Question 2

2 marks

Role and mechanism of a failover system

System fundamentals

(a)

2 marks

Identify that a failover system maintains a redundant, standby secondary server or system constantly synchronized with the primary platform.
Describe how it operates: when a hardware fault, power disruption, or software crash disables the primary system, the failover mechanism seamlessly switches operations to the secondary system automatically, avoiding disruption to end users.

Mentor tip

Emphasize automatic takeover by a redundant standby system during primary failure to preserve availability.

Question 3

2 marks

Role of the Control Unit (CU) in the CPU

Computer organisation

(a)

2 marks

State the primary function of the Control Unit: fetching instructions from main memory (RAM) and decoding them into micro-operations and control signals.
Outline its coordination role: directing the timing and movement of data between CPU registers, the Arithmetic Logic Unit (ALU), and input/output interfaces across the control bus.

Mentor tip

Focus on instruction fetching/decoding and issuing synchronization control signals to CPU components.

Question 4

3 marks

Truth table construction for A XOR (B OR C)

Computer organisation

(a)

3 marks

Evaluate the sub-expression (B OR C) for all 8 input combinations of binary inputs A, B, and C.
Apply the exclusive-OR (XOR) operator between input A and the intermediate result (B OR C), outputting 1 if and only if exactly one operand is true:
Row 1: A=0, B=0, C=0 -> B OR C = 0 -> 0 XOR 0 = 0
Row 2: A=0, B=0, C=1 -> B OR C = 1 -> 0 XOR 1 = 1
Row 3: A=0, B=1, C=0 -> B OR C = 1 -> 0 XOR 1 = 1
Row 4: A=0, B=1, C=1 -> B OR C = 1 -> 0 XOR 1 = 1
Row 5: A=1, B=0, C=0 -> B OR C = 0 -> 1 XOR 0 = 1
Row 6: A=1, B=0, C=1 -> B OR C = 1 -> 1 XOR 1 = 0
Row 7: A=1, B=1, C=0 -> B OR C = 1 -> 1 XOR 1 = 0
Row 8: A=1, B=1, C=1 -> B OR C = 1 -> 1 XOR 1 = 0

A 00001111 B 00110011 C 01010101 B \lor C 01110111 A \oplus (B \lor C) 01111000

Mentor tip

Evaluate (B OR C) first as an intermediate column before applying the XOR operation with A.

Question 5

2 marks

Hexadecimal 3B representation in an 8-bit register

Computer organisation

(a)

2 marks

Convert hexadecimal digit 3 into 4-bit binary: 3_{16} = 0011_2.
Convert hexadecimal digit B (decimal 11) into 4-bit binary: B_{16} = 1011_2.
Concatenate the two 4-bit nibbles into an 8-bit byte: 00111011.

3 B_{16} = (00111011)_{2}

Mentor tip

Convert each hex character into its 4-bit nibble and ensure all 8 bits including leading zeros are present.

Question 6

1 mark

Two iterations of ascending bubble sort

Computational thinking, problem-solving and programming

(a)

1 mark

Initial array: [9, 11, 3, 4, 5, 7, 1, 2].
Pass 1 (left-to-right adjacent comparisons and swaps):
Compare 9 and 11: no swap [9, 11, ...]. Compare 11 and 3: swap -> [9, 3, 11, ...]. Compare 11 and 4: swap -> [9, 3, 4, 11, ...]. Compare 11 and 5: swap -> [9, 3, 4, 5, 11, ...]. Compare 11 and 7: swap -> [9, 3, 4, 5, 7, 11, ...]. Compare 11 and 1: swap -> [9, 3, 4, 5, 7, 1, 11, ...]. Compare 11 and 2: swap -> [9, 3, 4, 5, 7, 1, 2, 11]. Largest element 11 is placed in final index.
Pass 2: Compare 9 and 3: swap -> [3, 9, 4, 5, 7, 1, 2, 11]. Compare 9 and 4: swap -> [3, 4, 9, 5, 7, 1, 2, 11]. Compare 9 and 5: swap -> [3, 4, 5, 9, 7, 1, 2, 11]. Compare 9 and 7: swap -> [3, 4, 5, 7, 9, 1, 2, 11]. Compare 9 and 1: swap -> [3, 4, 5, 7, 1, 9, 2, 11]. Compare 9 and 2: swap -> [3, 4, 5, 7, 1, 2, 9, 11].
Result after two complete iterations: 3, 4, 5, 7, 1, 2, 9, 11.

Mentor tip

In ascending bubble sort, each pass bubbles the next largest remaining value to the right.

Question 7

3 marks

Virtual machines as abstraction for multi-platform software testing

Resource management

(a)

3 marks

Explain virtual machine abstraction: A virtual machine creates an emulated, self-contained software representation of physical hardware and target operating systems, abstracting away the specific underlying host computer architecture.
Explain why this aids multi-platform testing: Developers can run multiple distinct guest operating systems (e.g., Linux, Windows, macOS) simultaneously on a single host computer, without purchasing multiple distinct physical machines.
Describe execution independence: Intermediate bytecode or target binaries run inside the standardized VM environment, which translates or interprets instructions to host CPU calls, ensuring consistent behavior across diverse deployment targets.

Mentor tip

Emphasize software emulation that abstracts host hardware, allowing multi-OS testing on a single physical machine.

Question 8

3 marks

Resource allocation in collaborative Voice over IP (VoIP)

Networks

(a)

3 marks

Outline how VoIP functions in nationwide office collaboration: Voice and video streams are digitized, packetized, and transmitted across IP data networks instead of dedicated public switched telephone circuits, enabling unified communications (video conferencing, desktop sharing, presence indicators).
Explain bandwidth resource management: Video and audio streaming require continuous, predictable network bandwidth. Without Quality of Service (QoS) bandwidth reservation, high traffic loads cause packet jitter, latency, and packet loss, disrupting real-time meetings.
Discuss routing and network segregation: Routers must prioritize voice packets ahead of bulk web traffic or downloads, or route VoIP over dedicated virtual local area networks (VLANs) to prevent internal congestion from degrading call clarity.

Mentor tip

Address both the communication method (packetized audio/video) and specific resource constraints such as bandwidth and router QoS.

Question 9

4 marks

Operating system multitasking functions

Resource management

(a)

4 marks

Function 1 - Processor Management (CPU Scheduling): The operating system schedules CPU time slices across active processes using round-robin or priority preemptive scheduling algorithms, giving users the perception of simultaneous program execution.
Detail process isolation and context switching: The scheduler manages interrupts, saves register contents, and switches process states (Ready, Running, Blocked) cleanly without race conditions.
Function 2 - Memory Management: The operating system allocates distinct memory partitions or address spaces to each concurrent process to prevent unauthorized memory overwriting between applications.
Detail virtual memory handling: If multiple executing programs exceed physical RAM capacity, the OS manages paging to secondary storage swap space to sustain multitasking without application crashes.

Mentor tip

Select processor scheduling and memory allocation as the two key OS functions, elaborating on time slicing and process memory isolation.

Question 10

3 marks

Ethical considerations of workplace CCTV surveillance

System fundamentals

(a)

3 marks

State the organizational rationale vs privacy tension: Employers have a legitimate interest in safeguarding physical premises, company assets, and employee safety, but this must balance against the fundamental privacy rights and mental well-being of staff.
Provide an example of surveillance misuse: Constant, invasive camera monitoring of individual worker movements, social interactions, or productivity micro-behaviors can generate an atmosphere of distrust, harassment, or intimidation.
Explain preventive policies and controls: Management must establish clear, transparent surveillance policies defining camera locations (strictly prohibiting private spaces like restrooms), specifying retention periods, restricting video access to vetted security personnel, and barring unauthorized managerial use.

Mentor tip

Structure the discussion with the balance of rights, a concrete risk of surveillance abuse, and explicit organizational safeguards.

Questions 11–15 · 75 marks

Question 11

15 marks

University examination record system upgrade

System fundamentals

(a)

2 marks

Identify aspect 1: Access permissions and security control — establishing strict authorization hierarchies (e.g., student read-only access for personal transcripts vs exam officer administrative write access).
Identify aspect 2: Data volume, archiving schedules, and storage scalability — accommodating rapid record expansion for current students while archiving two-year-old student papers and preserving historical numerical grades.

Mentor tip

Highlight access privileges and data volume/frequency of access between current and past student records.

(b)

3 marks

Explain direct observation: Analysts directly shadow office staff as they interact with the existing system during everyday administrative routines.
Detail benefits of first-hand insight: It reveals practical workflows, data bottlenecks, user operational errors, and actual usage patterns that staff might overlook or underreport in questionnaires.
Explain how this shapes requirements: Direct qualitative evidence exposes unstated pain points, ensuring the proposed system retains effective current features while rectifying inefficiency and validation flaws.

Mentor tip

Direct observation provides unbiased, first-hand evidence of real user workflows and systemic bottlenecks.

(c)

3 marks

State the purpose of creating a prototype: Presenting a functional early model to the examination office to validate core workflows, forms, and user interfaces before full-scale coding begins.
Explain feedback and iterative refinement: Allowing administrative staff to test navigation, identify missing requirements, and suggest adjustments early, significantly lowering redesign costs.
Accelerate consensus and development: Ensuring technical developers and end-user stakeholders share an identical understanding of system specifications before committing resources.

Mentor tip

Explain that prototypes elicit early user feedback, clarify functional requirements, and prevent costly late-stage revisions.

(d)

4 marks

Problem 1 - Data loss and corruption during transfer: Moving extensive exam records and student grades across network protocols or storage drives introduces risks of incomplete transmissions, corrupted fields, or packet drops, leaving academic records truncated or invalid.
Discussion 1: Resolving data corruption requires robust validation algorithms (such as hash checksum verification), pre-migration database backups, and data integrity audits before decommissioning legacy databases.
Problem 2 - Incompatibility of database formats and data structures: Legacy databases may use obsolete field encodings, deprecated data types, or proprietary schemas that do not map directly into the modern database schema.
Discussion 2: Resolving format mismatches requires writing and thoroughly testing Extraction, Transformation, and Loading (ETL) scripts, which can lead to project delays and elevated implementation costs if exceptions occur.

Mentor tip

Name data loss/corruption and schema/format incompatibility, discussing consequences and validation requirements for each.

(e)

3 marks

Outline the economic cost of parallel running: The organization must finance duplicate infrastructure, running both old servers and new hardware concurrently.
Explain staffing and operational expenses: Staff must enter all grades and examination records twice into both systems to verify parity, demanding substantial overtime wages or temporary staffing.
Discuss risk mitigation value: Although operationally expensive, this investment eliminates the catastrophic economic liability of complete university data loss or operational shutdown should the new system fail unexpectedly.

Mentor tip

Focus on duplicate operational costs (staffing, power, dual entry) balanced against catastrophic failure insurance.

Question 12

15 marks

College campus network and access policies

Networks

(a)

4 marks

Explain reliability of wireless transmission: Wi-Fi signals fluctuate based on physical distance from the access point, attenuation through building walls, electromagnetic interference from surrounding electronic appliances, and radio channel saturation when many students connect simultaneously.
Explain reliability of Ethernet transmission: Wired connections provide consistent, dedicated bandwidth with physical shielding inside twisted-pair cabling, making data transmission stable and immune to external radio interference.
Compare physical vulnerability: Ethernet links remain reliably connected provided cables and physical RJ-45 ports remain undamaged, whereas Wi-Fi experiences intermittent signal drops due to dynamic environmental interference.

Mentor tip

Contrast Wi-Fi susceptibility to radio interference, wall attenuation, and user density with the shielded stability of wired Ethernet.

(b)

4 marks

Feature 1 - Strong End-to-End Encryption: All payload packets traveling through the public internet are encrypted using symmetric ciphers (e.g., AES) so that any packet intercepted by a third party remains indecipherable.
Feature 2 - Tunneling and Encapsulation: VPN protocols (e.g., IPsec, OpenVPN) encapsulate entire original packets inside new IP headers with secure outer routing, concealing internal college IP addresses and packet metadata from eavesdroppers.
Feature 3 - Mutual Authentication: Both the client and the campus VPN gateway must authenticate using credentials, multi-factor tokens, or digital certificates before an authorized communication tunnel is established.

Mentor tip

Select encryption and tunneling/authentication as the two security features, explaining how each prevents unauthorized inspection.

(c)

1 mark

Identify one essential security protocol technology for VPN implementation: IPsec (Internet Protocol Security), TLS (Transport Layer Security), or SSL (Secure Sockets Layer).

Mentor tip

State a recognized tunneling/security protocol such as IPsec, TLS, or SSL.

(d)

6 marks

Advantage 1: Universal device synchronization and collaboration — cloud platforms allow students to co-edit shared project documents simultaneously across personal smartphones, home PCs, and college laptops without manual file copying.
Advantage 2: Modern feature availability and zero maintenance — commercial web services update continuously with advanced toolsets and abundant cloud storage exceeding what the college internal IT department can provision.
Disadvantage 1: Data sovereignty, security, and confidentiality risks — uploading sensitive research, student projects, or personal identification to third-party cloud servers exposes student data to external platform data breaches or unclear intellectual property terms.
Disadvantage 2: Academic misconduct and compliance issues — public blogs and unmonitored external platforms can facilitate plagiarism, defamatory postings, or cyberbullying outside the moderation and safeguarding purview of college IT policy.

Mentor tip

Balance collaborative flexibility and ubiquitous access against institutional compliance, data ownership, and moderation challenges.

Question 13

15 marks

Automated car park ticketing and tariff management

Abstract data structures
Resource management
Computational thinking, problem-solving and programming

(a)

2 marks

Explain dynamic memory allocation: The number of vehicles in the car park fluctuates constantly throughout the day; a linked list dynamically allocates and deallocates memory node-by-node without needing a pre-allocated fixed-capacity array.
Explain efficient node insertion: New ticket records can be appended or linked in constant time O(1) as cars arrive without needing to shift contiguous memory blocks.

Mentor tip

Link dynamic sizing and efficient runtime insertion to the unpredictable number of cars entering the facility.

(b)

2 marks

Part (i) - Concurrent processes: Raising the entrance barrier and raising the exit barrier simultaneously, or a customer paying at an automatic payment kiosk while the entrance barrier is being raised for an incoming vehicle.
Part (ii) - Non-concurrent processes: Updating the central available spaces display counter simultaneously by an entry process (decrementing) and an exit process (incrementing) without mutual exclusion, or simultaneously modifying the pointers of the shared linked list.

Mentor tip

Physical barrier movements on separate gates can happen concurrently; modifying shared counters or list pointers concurrently causes race conditions.

(c)

1 mark

Identify the validation check: The exit terminal must verify that the ticket has been paid and that the elapsed time between payment and exit does not exceed the allowed threshold of 10 minutes:
Condition: (CurrentTime - PaidAt <= 10) AND (PaidOn == CurrentDate).

Elapsed Minutes = CurrentTime - PaidAt \leq 10

Mentor tip

State that elapsed time since payment must be within the 10-minute departure window.

(d)

3 marks

Step 1 - Process the leaving vehicle first at the exit: Check exit ticket -> raise exit barrier -> increment car park display counter (spaces available increases).
Step 2 - Prioritizing exit prevents deadlocks: By registering the newly freed space before admitting an incoming car, the display reflects accurate capacity.
Step 3 - Process incoming vehicle at the entrance: Check display > 0 -> issue entry ticket -> decrement car park display counter -> raise entrance barrier.

Mentor tip

Show that the exit sequence precedes the entry sequence so the display counter increments before decrementing, preventing false full-capacity lockouts.

(e)

2 marks

Identify memory implication: Leaving paid and exited ticket objects in the linked list causes the data structure to grow indefinitely, consuming increasing amounts of RAM over time.
Identify search latency implication: Linear sequential searching across an ever-growing linked list degrades ticket lookup efficiency from O(k) for active cars to O(N) over historical records, slowing barrier response times.

Mentor tip

Explain that failing to remove historical records causes memory bloat and degrades sequential search latency.

(f)

5 marks

Calculate the date difference between arrival date (AD) and payment date (PD).
If the stay spans across dates (PD != AD):
Compute excess days: XD = PD - AD. Apply overnight daily cap: Total = XD * 60.00 EUR (or XD * 30.00 EUR per day). For consecutive days as specified in the rules, stay across two consecutive days costs 60.00 EUR.
Else (stay is within the same calendar day), compute parking duration DRN in minutes from arrival time to payment time:
Case 1: DRN <= 30 -> Fee = RULES[0][0] = 0.50 EUR.
Case 2: 30 < DRN <= 120 -> Fee = RULES[0][1] = 3.00 EUR.
Case 3: 120 < DRN <= 150 -> Fee = RULES[0][1] + RULES[1][0] = 3.00 + 5.00 = 8.00 EUR.
Case 4: 150 < DRN <= 240 -> Fee = RULES[0][1] + RULES[1][1] = 3.00 + 15.00 = 18.00 EUR.
Case 5: DRN > 240 -> Fee = RULES[1][2] = 30.00 EUR.
Output the calculated total fee.

Fee = ⎩ ⎨ ⎧ 60.00 0.50 3.00 8.00 18.00 30.00 if PaidDate > ArrivalDate if DRN \leq 30 if 30 < DRN \leq 120 if 120 < DRN \leq 150 if 150 < DRN \leq 240 if DRN > 240

Mentor tip

Check multi-day stays first before evaluating same-day duration brackets against the RULES table.

Question 14

15 marks

Mobile app restaurant location and review analytics

Computational thinking, problem-solving and programming
Control systems
Abstract data structures
System fundamentals

(a)

1 mark

Locate Zone [2] in the RESULTS table (the zone furthest from the user).
Sum all restaurants across the three price categories for Zone [2]: 2 + 3 + 1 = 6 restaurants.

2 + 3 + 1 = 6

Mentor tip

Sum the row values across Zone [2] in the RESULTS matrix: 2 + 3 + 1 = 6.

(b)

4 marks

Step 1 - GPS Trilateration: The smartphone GPS receiver captures atomic time-stamped radio signals from at least 3 (preferably 4) orbital GPS satellites, solving geometric sphere equations to determine exact user coordinates (latitude, longitude).
Step 2 - Map coordinate projection: The smartphone application plots the user coordinate at the center of the local geographic map scaled to current screen zoom levels.
Step 3 - Concentric zone calculation: The app computes Euclidean or Haversine distance radii from the center coordinate.
Step 4 - Display rendering: The system renders concentric boundary circles for Zone 0, Zone 1, and Zone 2 around the user position on the digital map overlay.

Mentor tip

Detail trilateration from satellite signals to establish user coordinates, followed by drawing radial concentric circles on the map.

(c)

5 marks

Initialize tracking variables: MAX_LIKES = -1, BEST_RESTAURANT = "".
Traverse collection LIKES sequentially while LIKES.hasNext():
Read four consecutive items per restaurant: ZONE = LIKES.getNext(), NUM_LIKES = LIKES.getNext(), NAME = LIKES.getNext(), RATING = LIKES.getNext().
Check if ZONE == 1: if true and NUM_LIKES > MAX_LIKES, update MAX_LIKES = NUM_LIKES and BEST_RESTAURANT = NAME.
After completing traversal across the collection, output BEST_RESTAURANT.

Mentor tip

Step through the collection four elements per entity (zone, likes, name, rating) and maintain the maximum likes for Zone 1.

(d)

3 marks

Construct three separate binary search trees (BST_0, BST_1, BST_2), one dedicated to each distance zone.
Populate BSTs from LIKES: Parse the collection in 4-tuples; use the zone identifier to route the entry to the corresponding tree, inserting a node with key = NUM_LIKES and value = restaurant data (inserting smaller keys in left subtree, larger keys in right subtree).
Traverse each tree in-order (or reverse in-order for descending popularity) to generate an ordered list for each zone, then concatenate the three lists in sequence: Zone 0, then Zone 1, then Zone 2.

Mentor tip

Build one binary search tree per zone keyed on likes, then perform in-order traversals and concatenate the resulting lists.

(e)

2 marks

Identify disadvantage: Online customer reviews can be biased, malicious, or fabricated.
Elaborate on business impact: Competitors or disgruntled individuals can post fake negative reviews, while reputation marketing firms create artificial positive ratings, distorting authentic consumer perception and damaging restaurant revenue without fair recourse.

Mentor tip

Explain that online review systems are vulnerable to fake or unverified feedback that unfairly distorts business reputation.

Question 15

15 marks

Fibonacci recursion tracing and iterative optimization

Computational thinking, problem-solving and programming
Abstract data structures

(a)

1 mark

Generate Fibonacci sequence terms starting from F_0 = 0, F_1 = 1:
F_0=0, F_1=1, F_2=1, F_3=2, F_4=3, F_5=5, F_6=8, F_7=13, F_8=21.
The 8th term is 21.

F_{8} = 21

Mentor tip

Ensure index matching starting at F_0 = 0 up to F_8 = 21.

(b)

3 marks

Trace recursive calls for fibo(4):
Level 1: fibo(4) = fibo(3) + fibo(2)
Level 2: fibo(3) expands to fibo(2) + fibo(1); fibo(2) expands to fibo(1) + fibo(0)
Level 3: Left fibo(2) expands to fibo(1) + fibo(0)
Substitute base cases: fibo(1) = 1, fibo(0) = 0:
Left subtree: fibo(3) = (1 + 0) + 1 = 2
Right subtree: fibo(2) = 1 + 0 = 1
Final summation: fibo(4) = 2 + 1 = 3.

fibo (4) = fibo (3) + fibo (2) = (fibo (2) + fibo (1)) + (fibo (1) + fibo (0)) = ((fibo (1) + fibo (0)) + 1) + (1 + 0) = ((1 + 0) + 1) + 1 = 3

Mentor tip

Show the full expansion tree down to base cases fibo(1)=1 and fibo(0)=0 before summing up to 3.

(c)

6 marks

Construct iterative algorithm to calculate the Nth Fibonacci number in O(N) time and O(1) space:
Pseudocode:
fiboIterative(N)
if N == 0 then return 0
if N == 1 then return 1
PREV2 = 0
PREV1 = 1
CURRENT = 0
loop I from 2 to N
CURRENT = PREV1 + PREV2
PREV2 = PREV1
PREV1 = CURRENT
end loop
return CURRENT
end fiboIterative

Mentor tip

Handle base cases 0 and 1, initialize two tracking variables, loop from 2 to N, and update variables iteratively.

(d)

3 marks

Construct procedure to output the first N terms of the Fibonacci sequence using fibo():
outputFirstN(N)
loop I from 0 to N - 1
output(fibo(I))
end loop
end outputFirstN
Each iteration calls fibo(I) and outputs the generated term.

Mentor tip

Set up a loop from index 0 to N-1, calling fibo(I) and outputting the result in sequence.

(e)

2 marks

Explain call stack push: Each time a recursive function call occurs, a new stack activation frame containing local variables, parameters, and the return address is pushed onto the system call stack.
Explain call stack pop: When a base case is reached, the function completes execution, returning its computed value and popping the activation frame off the stack to resume execution in the calling routine.

Mentor tip

Describe pushing activation frames (return address and local variables) on invocation, and popping frames upon return.

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 programming26 marks · 26%
Q6, Q13, Q14, Q15
System fundamentals24 marks · 24%
Q1, Q2, Q10, Q11, Q14
Networks18 marks · 18%
Q8, Q12
Resource management12 marks · 12%
Q7, Q9, Q13
Abstract data structures9 marks · 9%
Q13, Q14, Q15
Computer organisation7 marks · 7%
Q3, Q4, Q5
Control systems4 marks · 4%
Q14

Mentor insights

Traps to watch for

01
Boolean operator precedence in A XOR (B OR C) · Q4
The OR expression inside parentheses must be evaluated first. Only rows where A and (B OR C) differ in truth value produce an output of 1.
02
Car park ticket linked list accumulation · Q13
Leaving paid tickets in the linked list degrades lookup times from O(1) or O(active) to O(N) linear scans across all historic entries, and risks memory exhaustion.
03
Exponential call overhead in naive recursive Fibonacci · Q15
Tracing fibo(4) requires 9 total function calls due to repeated recalculation of identical subproblems (fibo(2) is calculated twice), demonstrating why dynamic programming or iteration is superior.

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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