The Kenya National Examinations Council
CRAFT CERTIFICATE IN INFORMATION TECHNOLOGY
OPERATING SYSTEMS
Time: 3 hours
July 2017
Instructions to Candidates:
This paper consists of TWO sections A and B. Answer ALL the questions in section A and FOUR questions from section B in the answer booklet provided.
Candidates should answer the questions in English.
SECTION A (40 Marks)
1. With the aid of a diagram, describe circular wait as used in process management.
Answer: Circular wait refers to a condition where a set of processes are waiting for each other in a circular chain, leading to a deadlock situation.
2. Outline the function of each of the following as used in operating systems:
(a) disk fragmentation
(b) device driver
Answer:
(a) Disk fragmentation is the scattering of parts of a file in different locations on a disk, slowing down access.
(b) A device driver is software that controls a specific hardware component of the computer.
3. Distinguish between monoprogramming and multiprogramming as used in operating systems.
Answer: Monoprogramming allows only one program to run at a time, whereas multiprogramming allows multiple programs to be loaded into memory and executed simultaneously.
4. A user wants to acquire a disk operating system for their computer. Outline four characteristics of operating systems that the user should consider.
Answer: (i) Compatibility, (ii) Performance, (iii) Security features, (iv) Support for multitasking.
5. Distinguish between hard real-time and soft real-time as used in operating systems.
Answer: Hard real-time systems guarantee task completion within a fixed time, whereas soft real-time systems aim for timeliness but do not guarantee it.
6. Karibu, a system provider for Adex Company, has advised the management to acquire a layered operating system. Explain two advantages of this operating system that would convince the company.
Answer:
(i) Modularity – Layers can be updated independently, improving maintenance.
(ii) Security – Each layer can restrict access to its functions, increasing system security.
7. Identify the following options when trying to install an operating system:
(a) upgrade
(b) repair
Answer:
(a) Upgrade involves updating the OS to a newer version.
(b) Repair fixes issues in the current installation without deleting data.
8. Explain the function of each of the options in safe mode.
Answer: Safe mode is used to boot the system with only essential files and drivers for troubleshooting issues.
9. Explain the function of each of the following as used in operating systems:
(a) Job control language
(b) Reentrant language
Answer:
(a) Job control language manages the execution of jobs in batch processing systems.
(b) Reentrant language allows multiple instances of the same program to run simultaneously without interference.
10. Explain the circumstances that would necessitate each of the following in recovery management:
(a) page fault
(b) trap
Answer:
(a) A page fault occurs when a program tries to access data that is not in memory, requiring the OS to retrieve it from disk.
(b) A trap is triggered by an error or special condition requiring the OS’s intervention.
11. The management of Adex Company has installed a distributed operating system for their operations. Explain two reasons for this move.
Answer:
(i) Increased efficiency – Distributed systems allow for sharing resources across multiple machines.
(ii) Fault tolerance – The system can continue to operate even if one component fails.
SECTION B (60 Marks)
Answer any FOUR questions in this section.
12. (a) Outline three functions of the kernel as applied in computer systems.
(b) Describe each of the following CPU time-scheduling algorithms:
(i) shortest job first
(ii) round-robin
(iii) first-come, first-served
(c) With the aid of a diagram, describe segmentation as used in memory management.
(d) Explain a circumstance that would necessitate the use of disk allocation in a computer system.
Answer:
(a) Kernel functions include managing resources, scheduling tasks, and handling system calls.
(b) Scheduling algorithms:
(i) Shortest job first – Executes the process with the smallest CPU burst first.
(ii) Round-robin – Time slices are assigned to each process in a circular order.
(iii) First-come, first-served – Processes are executed in the order they arrive.
(c) Segmentation divides memory into segments based on the logical divisions of a program.
(d) Disk allocation is required when disk space must be assigned to files in an efficient manner.
13. (a) List three types of read-only memory in a computer system.
(b) With the aid of a diagram, distinguish the following types of paper allocation as used in the best fit and worst fit:
(i) best fit
(ii) worst fit
(c) A company wants to implement an operating system with an NT file system over the existing FAT system. Explain three reasons for its recommendation.
(d) With the aid of an example, describe the absolute file path as used in file management.
(e) Explain the function of each of the following:
(i) RAID disks
(ii) cache memory
Answer:
(a) Types of ROM: (i) PROM, (ii) EPROM, (iii) EEPROM.
(b) Best fit – Allocates the smallest free partition that fits the request. Worst fit – Allocates the largest available partition.
(c) NTFS advantages: improved security, better file compression, and support for large files.
(d) Absolute file path specifies the complete path from the root directory.
(e) RAID disks provide redundancy, improving data reliability. Cache memory speeds up access to frequently used data.
14. (a) Define audit trail as used in operating system security.
(b) Explain each of the following types of computer file allocation:
(i) indexed
(ii) linked
(c) Explain the difference between quick format and full format as used in operating systems.
(d) With the aid of a diagram, describe a device process tree as used in process management.
Answer:
(a) Audit trail is a record of activities for security purposes.
(b) Indexed allocation uses a separate index to keep track of file locations, while linked allocation connects blocks using pointers.
(c) Quick format removes files without scanning the disk, while full format erases all files and scans for bad sectors.
(d) A device process tree shows parent-child relationships among processes.
15. (a) Define each of the following as used in operating systems:
(i) fuzzy semantics
(ii) list monadics
(b) Describe the components of computer resources as used in operating systems.
(c) With the aid of a diagram, describe round-robin scheduling as used in operating systems.
(d) Figure 1 shows a computer desktop icon. Use it to answer the question that follows.
Answer:
(a) Fuzzy semantics deal with approximate meanings, while list monadics refer to operations involving lists.
(b) Computer resources include CPU, memory, I/O devices, and files.
(c) Round-robin scheduling involves giving each process a fixed time slice to execute.