National Exit Exam – Bachelor of Science in Computer Science (BSc CS) — Questions and Answers

Question 1: Which switching method begins forwarding a frame as soon as the destination MAC address is read, without waiting for the full frame?

Adaptive switching
Cut-through (Correct answer)
Store-and-forward
Fragment-free

Correct answer: Cut-through

Cut-through switching begins forwarding after reading only the first 6 bytes (destination MAC), offering the lowest latency but no error checking.

Question 2: Which concurrency control technique uses timestamps to order transactions?

Optimistic concurrency control
Timestamp ordering protocol (Correct answer)
Multiversion concurrency control
Two-phase locking

Correct answer: Timestamp ordering protocol

The Timestamp Ordering Protocol assigns each transaction a timestamp and uses it to serialize conflicting operations.

Question 3: Which join returns only rows that have matching values in both tables?

LEFT OUTER JOIN
FULL OUTER JOIN
RIGHT OUTER JOIN
INNER JOIN (Correct answer)

Correct answer: INNER JOIN

INNER JOIN returns only the rows where the join condition is satisfied in both tables.

Question 4: What is the chromatic number of a graph?

The number of connected components
The maximum degree of any vertex
The number of edges in the graph
The minimum number of colors needed to color vertices so no two adjacent vertices share a color (Correct answer)

Correct answer: The minimum number of colors needed to color vertices so no two adjacent vertices share a color

The chromatic number χ(G) is the minimum number of colors required for a proper vertex coloring of graph G.

Question 5: What does SOLID stand for in object-oriented design principles?

Simple, Open, Logical, Integrated, Dynamic
Structured, Object, Linked, Interface, Design
Single, Optimized, Linked, Interface, Dependency
Single, Open, Liskov, Interface, Dependency (Correct answer)

Correct answer: Single, Open, Liskov, Interface, Dependency

SOLID stands for Single responsibility, Open/closed, Liskov substitution, Interface segregation, and Dependency inversion.

Question 6: What is the difference between a compiled language and an interpreted language?

Interpreted languages require an OS; compiled languages do not
Compiled languages are slower; interpreted languages are faster
Compiled languages use more memory; interpreted languages do not
Compiled code is translated to machine code ahead of time; interpreted code is executed line by line at runtime (Correct answer)

Correct answer: Compiled code is translated to machine code ahead of time; interpreted code is executed line by line at runtime

Compiled languages like C++ translate the entire program to machine code before execution, while interpreters like Python execute source code line by line.

Question 7: What type of cable is required for a direct connection between two computers without a switch (a cross-connect)?

Coaxial cable
Straight-through cable
Crossover cable (Correct answer)
Rollover (console) cable

Correct answer: Crossover cable

A crossover cable swaps the transmit and receive pairs, allowing two similar devices (e.g., two PCs) to communicate directly without an intermediary switch.

Question 8: What is a SQL injection attack?

An attack that encrypts SQL database files and demands ransom
An attack that physically damages SQL server hardware
An attack that inserts malicious SQL code into input fields to manipulate a database (Correct answer)
An attack that denies legitimate users access to a SQL database

Correct answer: An attack that inserts malicious SQL code into input fields to manipulate a database

SQL injection exploits unsanitized input fields by embedding malicious SQL statements that manipulate, expose, or destroy database contents when executed by the server.

Question 9: What is the primary purpose of a Translation Lookaside Buffer (TLB) in virtual memory systems?

To cache recent virtual-to-physical address mappings (Correct answer)
To handle page faults
To manage free frame lists
To store recently accessed pages from disk

Correct answer: To cache recent virtual-to-physical address mappings

The TLB is a hardware cache that stores recent virtual-to-physical page number translations to speed up memory access.

Question 10: Which software metric measures the degree to which components depend on one another?

Cohesion
Coupling (Correct answer)
Complexity
Coverage

Correct answer: Coupling

Coupling measures how strongly one module depends on another; low coupling is desirable for maintainability.

Question 11: What does the view frustum in 3D graphics define?

The field of diffuse lighting
The polygon budget per frame
The region of 3D space visible to the camera (Correct answer)
The mipmap level selection range

Correct answer: The region of 3D space visible to the camera

The view frustum is the truncated pyramid-shaped volume that contains all geometry potentially visible from the camera.

Question 12: What is the purpose of the 'nice' value in Unix/Linux process scheduling?

It adjusts the scheduling priority, with higher nice values yielding lower priority (Correct answer)
It sets the hard real-time priority of a process
It limits the CPU time a process can consume per second
It determines which CPU core the process is pinned to

Correct answer: It adjusts the scheduling priority, with higher nice values yielding lower priority

The nice value ranges from -20 (highest priority) to +19 (lowest priority); a process with a higher nice value is more 'generous,' yielding CPU time to others.

Question 13: What does the logical connective ¬ (NOT) do?

Combines two propositions with AND
Negates the truth value of a proposition (Correct answer)
Checks equivalence of two propositions
Implies one proposition from another

Correct answer: Negates the truth value of a proposition

The NOT operator negates a proposition: if P is true, ¬P is false, and vice versa.

Question 14: The task of establishing whether a bipartite graph possesses a perfect matching is best transformed into which other problem?

finding a Hamilton cycle in a simple graph.
finding the maximum flow in a directed network. (Correct answer)
finding the longest path in a directed network.
finding a vertex cover in a simple graph.

Correct answer: finding the maximum flow in a directed network.

The problem of finding a perfect matching in a bipartite graph can be efficiently transformed into a maximum flow problem. By constructing a flow network with a source, a sink, and unit capacity edges, a perfect matching exists if and only if the maximum flow from the source to the sink equals the number of vertices in one partition of the bipartite graph. This reduction allows standard maximum flow algorithms to solve the matching problem.

Question 15: Which algorithm efficiently clips a line segment to a rectangular window?

Bresenham's algorithm
Scanline fill
Sutherland-Hodgman
Cohen-Sutherland (Correct answer)

Correct answer: Cohen-Sutherland

The Cohen-Sutherland algorithm assigns region codes to line endpoints and uses them to trivially accept, reject, or clip line segments against a window.

Question 16: When incorporating AI algorithms, what ethical hazard should one be vigilant about?

Over-optimization
Algorithm complexity
Lack of computational power
Bias and unintended criteria (Correct answer)

Correct answer: Bias and unintended criteria

A significant ethical hazard when incorporating AI algorithms is the potential for bias and unintended criteria. AI models learn from the data they are trained on, and if this data contains historical biases or reflects societal inequalities, the AI can perpetuate or even amplify these biases in its decisions. This can lead to unfair or discriminatory outcomes, necessitating careful vigilance during development and deployment.

Question 17: What is the term for an operating system that is stored on a ROM chip within a mobile device or consumer electronic device?

Mobile OS (Correct answer)
Free OS
Stand-alone OS
Server OS

Correct answer: Mobile OS

A mobile operating system is specifically designed to run on mobile devices like smartphones, tablets, and other consumer electronics. These operating systems are often stored on a ROM (Read-Only Memory) chip within the device, allowing for quick boot-up and efficient resource management tailored to portable hardware. Examples include iOS and Android.

Question 18: In the context of AI, what is the meaning of the term "agent"?

An entity that perceives and acts (Correct answer)
A robotic humanoid
A program that simulates human thinking
Something that performs human-like tasks

Correct answer: An entity that perceives and acts

In the context of AI, an 'agent' is defined as anything that can perceive its environment through sensors and act upon that environment through effectors. This broad definition includes humans, robots, software programs, and even thermostats. The agent's goal is to perform actions that maximize its performance measure based on its perceptions.

Question 19: What is a firewall's primary function in network security?

To authenticate users attempting to access network resources
To scan files for malware before they are downloaded
To monitor and control incoming and outgoing network traffic based on predefined security rules (Correct answer)
To encrypt all network traffic between endpoints

Correct answer: To monitor and control incoming and outgoing network traffic based on predefined security rules

A firewall enforces security policies by filtering network traffic according to rules, acting as a gatekeeper between trusted internal networks and untrusted external networks.

Question 20: In Scrum, who is responsible for maximizing the value of the product?

Stakeholder
Development Team
Product Owner (Correct answer)
Scrum Master

Correct answer: Product Owner

The Product Owner owns the product backlog and prioritizes work to maximize value delivered.

Question 21: What is the difference between CISC and RISC architectures?

CISC has many complex instructions; RISC has fewer, simpler ones (Correct answer)
CISC runs faster; RISC uses less power
CISC uses fewer, simpler instructions; RISC uses many complex ones
CISC is used in phones; RISC is used in desktops

Correct answer: CISC has many complex instructions; RISC has fewer, simpler ones

CISC (Complex Instruction Set Computer) has many specialized instructions, while RISC uses a small set of simple, fast instructions.

Question 22: What does DMA stand for and what does it do?

Distributed Memory Array — connects RAM modules
Direct Memory Access — transfers data without CPU involvement (Correct answer)
Dynamic Memory Allocation — allocates RAM dynamically
Data Management Architecture — organizes storage

Correct answer: Direct Memory Access — transfers data without CPU involvement

DMA (Direct Memory Access) allows peripherals to read/write memory directly, freeing the CPU for other tasks.

Question 23: What process involves merging multiple images to create a single new image?

Warping
Morphing (Correct answer)
Animation
Modeling

Correct answer: Morphing

Morphing is a computer graphics technique that seamlessly transforms one image or shape into another. It involves creating a smooth transition by gradually distorting the source image and blending it with the target image, often used to create special effects where one object appears to 'morph' into another.

Question 24: Which protocol allows two parties to establish a shared cryptographic secret over an insecure channel without transmitting the secret itself?

MD5
Diffie-Hellman key exchange (Correct answer)
RSA
AES

Correct answer: Diffie-Hellman key exchange

The Diffie-Hellman key exchange enables two parties to compute the same shared secret using public values and their own private values, without ever sending the secret across the channel.

Question 25: Which number system uses base 16?

Octal
Binary
Hexadecimal (Correct answer)
Decimal

Correct answer: Hexadecimal

Hexadecimal uses 16 symbols (0–9 and A–F) and is commonly used to represent memory addresses and color codes.

Question 26: A stored procedure in SQL differs from a function primarily because a stored procedure:

Cannot accept parameters
Can return multiple result sets and does not have to return a value (Correct answer)
Is always executed automatically on data change
Can only be called from another stored procedure

Correct answer: Can return multiple result sets and does not have to return a value

Stored procedures can return multiple result sets, execute DML statements, and are not required to return a single value like functions.

Question 27: What is the function of the memory address register (MAR)?

Stores data read from memory
Holds the address of memory to be read or written (Correct answer)
Counts memory accesses
Manages virtual memory mapping

Correct answer: Holds the address of memory to be read or written

The MAR holds the address of the memory location currently being accessed during a read or write operation.

Question 28: What is operator overloading?

Using too many operators in one expression
Using bitwise operators instead of arithmetic ones
Defining custom behavior for operators when applied to user-defined types (Correct answer)
Overriding built-in operators with system calls

Correct answer: Defining custom behavior for operators when applied to user-defined types

Operator overloading allows programmers to define how standard operators (like +, ==) behave for user-defined classes.

Question 29: What does cyclomatic complexity measure?

Memory usage of a program
Lines of code
Runtime performance
Number of independent paths through code (Correct answer)

Correct answer: Number of independent paths through code

Cyclomatic complexity counts the number of linearly independent paths through a program's source code.

National Exit Exam – Bachelor of Science in Computer Science (BSc CS)

Ethiopia's Ministry of Education national exit examination assessing BSc Computer Science graduates across six core themes: system development, programming and algorithms, computer networking and security, intelligent systems, computer architecture and OS, and compiler theory.

Questions

35 min

Time Limit

50%

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