1937/016 OPERATING SYSTEMS July 2019 Time: 3 hours
THE KENYA NATIONAL EXAMINATIONS COUNCIL
CRAFT CERTIFICATE IN INFORMATION TECHNOLOGY
MODULE II
OPERATING SYSTEMS
3 hours
INSTRUCTIONS TO CANDIDATES:
This paper consists of TWO sections, A and B.
Answer ALL the questions in section A and any FOUR from section B.
Answers to ALL the questions must be written in the answer booklet provided.
Candidates should answer the questions in English.
This paper consists of 4 printed pages.
The candidate should check the question paper to ascertain that all the pages are printed and indicate that no questions are missing.
© 2019 The Kenya National Examinations Council.
SECTION A (40 marks)
Answer ALL the questions in this section.
1. Richard intends to install an operating system in his new computer. Explain three requirements that should be considered before installation.
Answer:
Hardware compatibility: Ensure that the system’s hardware, such as the processor, RAM, and storage, meets the operating system’s requirements.
Software compatibility: Verify that essential software applications are supported by the new operating system.
Licensing: Confirm that a proper license is obtained for the operating system to ensure legal use and regular updates.
2. Describe each of the following disk scheduling algorithms as used in operating systems:
(a) shortest seek time first
(b) elevator disk scheduling
Answer:
(a) Shortest seek time first (SSTF): This algorithm selects the disk request that requires the least movement of the read/write head from its current position, thereby reducing seek time.
(b) Elevator (SCAN) scheduling: The disk arm moves in one direction fulfilling requests until it reaches the end, then reverses direction. This method works similarly to an elevator.
3. Explain the advantages of flash memory over compact disks storage media.
Answer:
Faster read/write speeds compared to compact disks.
Greater durability since flash memory has no moving parts, making it more shock-resistant.
Flash memory is more compact and portable compared to compact disks.
4. Network Computing Ltd., a mobile communications device manufacturer intends to install the android mobile operating system in their new devices. Explain two advantages the company would gain from using this operating system.
Answer:
Open-source nature: Android is open source, allowing the company to customize the OS for their devices at no additional cost.
Large developer ecosystem: Android’s vast developer community ensures constant innovation and availability of applications.
5. Define each of the following terms as used in operating systems:
(a) multiprogramming
(b) multi-tasking
Answer:
(a) Multiprogramming: A method where multiple programs are loaded into memory and the processor switches between them, improving resource utilization.
(b) Multi-tasking: The ability of an operating system to run multiple tasks (programs) simultaneously by sharing CPU time.
6. With the aid of a diagram, describe paging as applied in operating systems.
Answer: Paging is a memory management scheme that eliminates the need for contiguous allocation of physical memory. The operating system divides the physical memory into fixed-size blocks called pages. Each process is divided into pages and loaded into available memory frames, allowing more efficient use of memory. [Include diagram of page mapping.]
7. Define each of the following terms as used in operating systems:
(a) polling
(b) pipe
Answer:
(a) Polling: A technique where the CPU continuously checks the status of a device or service to see if it requires attention.
(b) Pipe: A method used to enable inter-process communication by allowing the output of one process to be used as input for another.
8. Explain the two functions of directories in a computer system.
Answer:
Organizational structure: Directories organize files into a hierarchical structure, making it easier to manage and locate files.
Metadata storage: Directories store important information about files such as their size, permissions, and creation dates.
9. Computer users are advised to set strong passwords to protect their devices. Outline three characteristics that these passwords should possess.
Answer:
Length: A strong password should be at least 12 characters long.
Complexity: It should contain a mix of uppercase letters, lowercase letters, numbers, and special characters.
Unpredictability: Avoid using common words, phrases, or easily guessable information like birthdates.
10. Differentiate between dynamic loading and dynamic linking as used in memory management.
Answer:
Dynamic loading: The process of loading a program into memory only when it is required, allowing for more efficient use of resources.
Dynamic linking: The process of linking the required external code libraries to a program at runtime rather than at compile time, reducing memory overhead.
SECTION B (60 marks)
Answer any FOUR questions in this section.
11. (a) Outline three reasons for implementing threads at the user level.
Answer:
Faster context switching: User-level threads can be managed more efficiently by the application.
No need for kernel mode privilege: Since user-level threads don’t require kernel interaction, operations are quicker.
Simplicity in scheduling: User-level threads can use application-defined scheduling policies without involving the kernel.
(b) Outline three differences between a process and a thread as applied in operating systems.
Answer:
Processes have their own memory space, whereas threads share the same memory space.
Processes are heavier (take more resources) compared to threads, which are lighter and faster to create.
Inter-process communication is more complex than inter-thread communication, which is simpler since threads share memory.
12. The process control block of an operating system comprises different types of information. List six types of this information.
Answer:
Process state
Process ID
Program counter
CPU registers
Memory management information
I/O status information
13. (a) Outline three advantages of an operating system that supports batch processing.
Answer:
Efficient resource utilization: Batch processing allows the system to process jobs without user interaction, maximizing system efficiency.
Reduced CPU idle time: Jobs are queued and executed one after another, reducing idle time for the CPU.
Automation: Batch jobs can be automated, allowing for hands-off operation of repetitive tasks.
(b) The computer system is made up of different buses that facilitate input/output processes. Explain three of these buses.
Answer:
Data bus: Carries data between the CPU, memory, and other devices.
Address bus: Transmits the memory address where data is to be read or written.
Control bus: Carries control signals like read/write operations and interrupt requests.
14. (a) Define the term virtual machine as applied in device management.
Answer:
A virtual machine (VM) is an emulation of a computer system that allows multiple operating systems to run on a single physical machine simultaneously, each operating as if it has its own hardware.
(b) Describe paging memory management techniques as used in operating systems.
Answer: Paging is a memory management technique where processes are divided into pages of equal size. These pages are loaded into memory frames, which do not need to be contiguous. This allows for more efficient use of memory and minimizes fragmentation.