Computer Science practice questions (Jahziah exam)

Area 01 · Algorithms, computability & complexity

A software engineer must implement a data structure that supports the following operations on a collection of distinct integer keys: insert a key, delete a key, search for a key, and retrieve the predecessor of a given key (the largest key strictly smaller than the given key). The application frequently performs all four operations, and the keys are drawn from a large range. A colleague suggests using a hash table with separate chaining, claiming that its expected O(1) average time for insert, delete, and search makes it the best choice. Which statement correctly analyzes why a balanced binary search tree is actually the more appropriate implementation for this workload?

Pick an answer to check yourself.

1. AA hash table cannot store integer keys, so a balanced binary search tree is required.
2. BA balanced binary search tree supports predecessor queries in O(log n) time, while a hash table provides no efficient way to find the predecessor because it does not maintain key order.
3. CA balanced binary search tree has O(1) worst-case time for insert, delete, and search, whereas a hash table degrades to O(n) in the worst case.
4. DA hash table requires more memory than a balanced binary search tree, making it impractical for large key sets.

Area 02 · Architecture & organization

A 8-bit ALU adds the two's complement values 0x6B and 0x5A and stores the low 8 bits in an 8-bit register. Which statement best analyzes the result and the flags it should set?

Pick an answer to check yourself.

1. AResult 0xC5, zero flag = 0, carry flag = 0, overflow flag = 0. Two positive operands produced a negative result pattern, so overflow should actually be flagged.
2. BResult 0xC5, with signed overflow set because two positive operands produced a negative result pattern, and carry out = 0.
3. CResult 0xC5, with carry flag set and signed overflow clear because both operands have the same sign.
4. DResult 0xC5, and the ALU should signal an unsigned overflow because the sum exceeds 127.

Area 03 · Discrete structures

In a breadth-first traversal of a tree starting from the root, which data structure is typically used to keep track of nodes to visit?

Pick an answer to check yourself.

1. AQueue
2. BStack
3. CPriority queue
4. DHash table

Area 04 · Information management

A database designer is describing the relational data model to a new team member. Which statement best explains the principle that underlies the relational model?

Pick an answer to check yourself.

1. AData is stored as objects that encapsulate both attributes and the methods that operate on them, so behaviour is stored together with each object.
2. BData is represented as relations (tables) of tuples, where each row is an instance and its values are drawn from a defined domain, and associations are expressed by matching key values.
3. CData is stored as a tree of records connected by parent-child pointers, so each child record has exactly one parent record.
4. DData is stored as a set of records linked by owner and member pointers forming a network, where a record may have several owners.

Area 05 · Networking

A small company network consists of three departmental LANs, each connected to a central router. This central router also connects to an ISP router, which forwards traffic across the public internet to a remote web server. A network engineer labels each device as either an edge or core component according to the standard internet structure model. Which classification is correct?

Pick an answer to check yourself.

1. AThe departmental LANs are part of the core, and the ISP router is part of the edge.
2. BThe departmental LANs are part of the edge, and the ISP router is part of the core.
3. CBoth the departmental LANs and the ISP router are part of the edge.
4. DBoth the departmental LANs and the ISP router are part of the core.

Area 06 · Operating systems

A device driver maintains a single I/O request queue for a disk. The queue is currently empty. Requests arrive in this order: X (service time 8 ms), Y (service time 2 ms), Z (service time 6 ms). The driver uses Shortest Job First (SJF) scheduling, which selects the request with the shortest service time from those currently waiting. When X arrives, it begins service immediately. While X is being served, Y and Z arrive and wait. After X completes, which request is served next and what is its waiting time?

Pick an answer to check yourself.

1. AY is served next; its waiting time is 0 ms.
2. BY is served next; its waiting time is 8 ms.
3. CZ is served next; its waiting time is 8 ms.
4. DX is served again; its waiting time is 0 ms.

Area 07 · Programming languages

A class `Temperature` stores a Celsius value in a private field `celsius`. The class provides a public method `setCelsius(double c)` that assigns the value but does not validate it. A client program sets `celsius` to −300 using this method. Which change best applies encapsulation to prevent invalid states, without exposing the internal field?

Pick an answer to check yourself.

1. AMake the field `celsius` public so that client code can directly read and write it, removing the need for a setter.
2. BIn the `setCelsius` method, reject values below absolute zero (0 K) before assigning to the field, and keep the field private.
3. CAdd a public getter `getCelsius()` and leave the setter unchanged, so clients can check the value after setting it.
4. DReplace the setter with a constructor that takes the Celsius value and assigns it directly to the field, without validation.

Area 08 · Software engineering

A bank is adopting an agile process for a mobile banking app. The team plans two-week iterations with a prioritized backlog and a demo at the end of each iteration. Which characteristic of agile processes does this plan most directly illustrate?

Pick an answer to check yourself.

1. AIterative and incremental delivery with customer feedback
2. BA single sequential pass through all lifecycle phases
3. CRisk-driven spirals with formal risk analysis each cycle
4. DFreezing all requirements before development starts