### cameroon gce A level June 2023 computer science 2

cameroon gce A level June 2023 computer science 2

(«) Which of direct access and sequential access takes a longer time? Explain your answer. (3 marks)

(h) (i) A double-sided DVD has a capacity of 8.5GB. How many CDs of 700MB storage capacity are

required to store information in a full double-sided DVD? (3 marks)

(ii) We want to build a circuit that can be used to add two 4-bit numbers. We have full adders and half

adders to use ns components.

(a) Explain the difference between a half-adder and a full-adder. (2 marks)

(b) Draw a block diagram of your circuit which shows how the numbers 1011 and 1110 are

being added, Show and label all inputs and outputs. Use at least one half-adder and at least

one full-adder.

(iii) Describe TWO characteristics of a CPU that can affect the overall performance of a computer.

(S marks)

(4 marks)

•M « (0 Consider the following 8-bit binary integer which is in two’s complement form.

I 1 1 0 1 0

(n) Give the denary equivalent of this binary integer.

Show how this binary integer \vbuld be represented in hexadecimal.

Show the result obtained when this binary integer is added to itself. State its decimal equivalent and

(3 marks)

(2 marks)

(b) (2 marks)

(c)

explain the result.

A RISC processor has a 32-bit architecture, with instructions that are 1-word long. The processor has 64

registers each of which is 32 bits long and supports 45 instructions (operations). Besides the operator field

which holds the operation code (Opcode), each instruction has an immediate operand and two register

operands. The Opcode field uses M bits to address 45 operations, each register operand uses N bits and the

remaining bits are used for the immediate operand field.

Determine the minimum number of bits required for the Opcode field.

Determine the minimum number of bits required for each register operand field.

Determine the maximum number of bits available for the immediate operand field.

State two key characteristics of this processor’s instruction set.

(ii)

(a)

(iii) Most conventional computers have a S1SD architecture.

(a) What does SISD stand for?

(b) Draw a block diagram that illustrates the SISD machine architecture.

(1 mark)

(3 marks)

3. (i) With reference to operating systems:

(a) Distinguish between paging and segmentation.

(b) State one important relationship between the operating system and computer hardware

(c) Describe the terms Real Time processing and Batch processing using real life scenarios as

examples to demonstrate their application.

(ii) Consider the following process handled in an operating system with the associated units of arrival and service

times:

PROCESS ARRIVAL TIME SERVICE TIME

PI 0 7

P2 2 4

P3 4 1

P4 5 4

(a) Using the Shortest Remaining Time First scheduling policy draw a Gantt chart for these processes.

(4 marks)

(4 marks)

(1 mark)

(b) Calculate the average waiting time and turnaround time for the processes

(c) Calculate the throughput of the operating system.