OCR ALevel ComputerScience Practice Exam

OCR ALEVEL

COMPUTERSCIENCE

PRACTICE EXAM

Question 1: Which component of the CPU acts as the temporary storage for the

results of calculations?

Choices:

1) Program Counter (PC) 2) Memory Address Register (MAR) 3) Accumulator (ACC) 4) Instruction Register (IR)

Correct Answer: Accumulator (ACC)

Explanation: The Accumulator is a special-purpose register within the Arithmetic Logic Unit (ALU) that holds the data currently being processed and the results of calculations.Page 1

Question 2: What is the primary e�ect of increasing the width of the data bus in a computer system?

Choices:

1) It increases the maximum clock speed of the CPU.2) It allows more data to be transferred between the CPU and memory in a single cycle.3) It increases the maximum amount of addressable memory.4) It reduces the physical size of the motherboard.Correct Answer: It allows more data to be transferred between the CPU and memory in a single cycle.Explanation: The data bus carries the actual data between the processor and memory.Increasing its width means more bits can be transferred simultaneously in a single clock cycle.

Question 3: Which of the following describes the Harvard architecture?

Choices:

1) Instruction data and operation data are stored in the same memory space.2) It uses a single bus for both instructions and data.3) It uses separate memory and buses for instructions and data.4) It relies exclusively on virtual memory for execution.

Correct Answer: It uses separate memory and buses for instructions and data.

Explanation: Harvard architecture separates the memory and buses for data and instructions, allowing the CPU to fetch an instruction and read/write data simultaneously, unlike Von Neumann architecture.Page 2

Question 4: Which scheduling algorithm uses a time-slice to allocate CPU time to each process equally?

Choices:

1) First Come First Served (FCFS) 2) Shortest Job First (SJF) 3) Round Robin 4) Multi-level Feedback Queue

Correct Answer: Round Robin

Explanation: Round Robin is a preemptive scheduling algorithm that assigns a �xed time-slice (quantum) to each process in the ready queue, cycling through them continuously.

Question 5: What is the primary function of a device driver?

Choices:

1) To protect the system from malware.2) To manage the translation of instructions between the operating system and a hardware device.3) To allocate RAM to application software.4) To compile high-level code into machine code.Correct Answer: To manage the translation of instructions between the operating system and a hardware device.Explanation: A device driver is a specialized software program that acts as a translator, allowing the operating system to communicate e�ectively with a speci�c hardware device.Page 3