SL · 75 minutes · 50 marks
Instructions
Answer every question in Section A and Section B.
The marks for each question are shown in square brackets, such as [3].
Answer on paper or on screen. Each question links to its own page, where you can type an answer and mark it against its marking points.
Times and marks follow public descriptions of the new course, which Spine has not yet checked against the IB's subject guide. Your school's mocks may differ.
Answer all questions.
The processor in a school library's self-checkout kiosk runs a program that adds up the fines on a student's account.
(a) State the function of the arithmetic logic unit (ALU). [1]
(b) State what is held in the program counter (PC). [1]
[2]
A weather station's processor is about to run the instruction LOAD 200, which copies the value stored at memory address 200 (the latest temperature reading) into the accumulator. The program counter currently holds 57, the address of this instruction.
Describe the fetch stage of the fetch, decode and execute cycle for this instruction, naming the registers and buses used. [4]
A freezer in a school canteen logs its temperature in degrees Celsius as an 8-bit two's complement integer.
(a) Convert -45 into 8-bit two's complement. Show your working. [2]
(b) Convert the 8-bit two's complement value 10011010 into denary. [1]
(c) State the range of whole numbers that 8-bit two's complement can store. [1]
[4]
A school greenhouse has three sensors, each giving 1 or 0.
A warning light X turns on when the temperature is too high and the window is closed, or when the soil is not moist.
(a) Write a Boolean expression for X. [1]
(b) Construct the truth table for X, with columns A, B, C and X. [3]
[4]
In a school's computer lab, 30 desktop computers are each connected by a cable to one device in the corner of the room. The lab is part of the school network, which connects to the internet. Tablets in the school library join the same network without cables.
(a) State the function of the switch that the 30 lab computers are connected to. [1]
(b) State the function of the school's router. [1]
(c) State the device that lets the library tablets join the school network without cables. [1]
[3]
A music school gives live online violin lessons over a video call. After each lesson, students upload a recording of their practice as a file.
(a) State one feature of TCP that the file uploads need. [1]
(b) Explain why UDP is often used for the live video call. [2]
[3]
A school sends end-of-term reports to 800 parents through an online portal. The reports must be encrypted while they travel over the internet.
(a) Compare symmetric and asymmetric encryption for this portal. Refer to how the keys are shared with parents and to the speed of each method. [5]
[5]
Identify the keys in this small school library database. It has two tables.
| Table | Fields |
|---|---|
| Book | book_id, title, author, year_published |
| Loan | loan_id, book_id, student_name, due_date, returned |
Every loan gets a new loan_id. The same book can be borrowed many times, so one book_id can appear in many Loan records.
(a) Identify the primary key of the Loan table. [1]
(b) Identify the foreign key in the Loan table, and explain how it links a loan to the book that was borrowed. [2]
[3]
A school library database has these two tables. In Loan, book_id is a foreign key to Book, and returned is a BOOLEAN.
Book
| book_id | title | author | year_published |
|---|---|---|---|
| 1 | Coral Reefs | Mbeki | 2019 |
| 2 | Dark Matter Basics | Ruiz | 2012 |
| 3 | Algorithms for Kids | Tanaka | 2021 |
| 4 | Bridges of Lisbon | Costa | 2016 |
| 5 | Eclipse Diaries | Okafor | 2015 |
Loan
| loan_id | book_id | student_name | due_date | returned |
|---|---|---|---|---|
| 1 | 3 | Ana | 2026-11-02 | FALSE |
| 2 | 1 | Ben | 2026-10-20 | TRUE |
| 3 | 2 | Chloe | 2026-10-28 | FALSE |
| 4 | 3 | Dev | 2026-10-15 | TRUE |
(a) Construct an SQL query that lists the titles of all books published after 2015, in alphabetical order of title. [2]
(b) Construct an SQL query that lists the student_name and the title of the book for every loan that has not been returned. [3]
[5]
A school canteen wants to estimate how many vegetarian lunches to cook each day. It is choosing between two solutions.
Solution 1 is a program in which the cook writes fixed rules, for example "cook 60, and 10 more on Fridays". Solution 2 is a machine learning model trained on two years of the canteen's daily sales records.
Outline how the way solution 2 gets its behaviour differs from the way solution 1 gets its behaviour. [2]
A city library is planning three systems. Identify the type of machine learning (supervised, unsupervised or reinforcement) that each one uses.
(a) A model is trained on 5000 past book reviews, each already tagged by staff as positive or negative. It then tags new reviews. [1]
(b) A model sorts library members into groups with similar borrowing habits. Nobody tells it what the groups should be. [1]
(c) A program controls a book-sorting robot arm. It gains a point for each book placed on the right shelf and loses a point for each book dropped, and it improves its movements over thousands of attempts. [1]
[3]
Section B is in the case-study format, on a practice scenario written by Spine. It is not the IB's case study for your exam year. Read the scenario first. Each question refers to it.
Practice scenario (written by Spine, not an IB case study):
Larkford is a small city with a community bike-share called LarkBikes. It has 40 docking stations, each with between 10 and 20 docks. Each dock has a sensor that detects whether a bike is locked in it and reads the bike's ID tag. Every station sends its sensor readings to a central server over the mobile phone network every 5 minutes.
Riders register in the LarkBikes app with their name, email address, home postcode and date of birth. When a rider unlocks a bike, a trip starts. The server keeps riders, bikes, stations and trips in a relational database. Each trip record holds the rider, the bike, the start station, the end station, and the start and end times. The database now holds two years of trips.
Every evening, a machine learning model is trained on the trip records together with the hour of the day, the day of the week, whether it is a school holiday, and the weather. For each station, it predicts how many bikes will be taken in each hour of the next day. A van crew uses these predictions to move bikes to stations that are expected to run out.
The 28 stations in the city centre are busy. The 12 stations in the outer districts were added last year and record far fewer trips.
(a) State whether the LarkBikes model performs classification or regression, and give a reason. [2]
(b) Identify one feature the model uses and the label it learns to predict. [2]
[4]
(a) Suggest a primary key for the Trip table, and explain why the rider's ID would not work as the primary key on its own. [2]
(b) Describe how the Trip table is linked to the Station table, and identify the relationship between Station and Trip. [2]
[4]
The model predicts few trips at the outer-district stations, so the van rarely brings bikes there. Riders in the outer districts often find those stations empty.
Discuss whether it is fair to use the model's predictions to decide where the van takes bikes. [4]