DICT OPERATING SYSTEM 2021

(a) Explain the role of operating systems in program development.
Operating systems provide essential tools and environments for program development, including compilers, debuggers, and editors.
(2 marks)

(b) Explain the role of operating systems in system access.
Operating systems manage system access by authenticating users, providing secure login, and maintaining access control to ensure only authorized users can interact with the system.
(2 marks)

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(a) Outline two typical characteristics of microkernel architecture operating systems.

1. Minimal core functions.
2. Modular components that run in user space.
   (2 marks)

(b) Explain four reasons that could necessitate the termination of a running process.

1. Completion: The process has finished its execution.
2. Error: The process encounters an unrecoverable error.
3. Resource Shortage: The system lacks the necessary resources to continue the process.
4. Manual Termination: The process is manually terminated by the user or system administrator.
   (8 marks)

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(a) Outline two typical attributes associated with computer files.

1. File name.
2. File size.
   (2 marks)

(b) Differentiate between memory paging and memory segmentation.

1. Paging: Memory is divided into fixed-size pages. Each page can be mapped to any physical memory location.
2. Segmentation: Memory is divided into segments based on logical divisions. Each segment can vary in size and can be mapped to different locations in physical memory.
   (4 marks)

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(a) Describe a multiprocessor system.
Multiprocessor systems have multiple CPUs that share a common memory and peripheral devices, enhancing performance and reliability.
(2 marks)

(b) Explain two advantages of a multiprocessor system that could have influenced the advice given to Youl Technical Institute.

1. Increased Performance: Multiple processors can handle more tasks simultaneously.
2. Fault Tolerance: If one processor fails, others can continue functioning, improving system reliability.
   (4 marks)

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(a) Explain the term “multithreading” as used in operating systems.
Multithreading is the ability of a CPU to execute multiple threads concurrently, improving efficiency and performance.
(2 marks)

(b) Explain the term “process” as used in operating systems.
A process is a program in execution, including its code, data, and system resources.
(2 marks)

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Outline four typical functions of the operating system kernel during process management.

1. Process scheduling.
2. Context switching.
3. Inter-process communication.
4. Resource allocation.
   (4 marks)

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7.

Differentiate between block-oriented and stream-oriented I/O devices.

1. Block-oriented: Data is handled in fixed-size blocks.
2. Stream-oriented: Data is handled as a continuous stream of bytes.
   (4 marks)

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Explain four requirements that the memory management design of an operating system should endeavor to satisfy.

1. Efficiency: Maximize the use of available memory.
2. Protection: Ensure that processes do not interfere with each other’s memory.
3. Allocation: Dynamic allocation and deallocation of memory.
4. Mapping: Efficiently map logical addresses to physical addresses.
   (8 marks)

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Outline four criteria that should be considered when selecting a file organization method.

1. Access speed.
2. Storage efficiency.
3. Data redundancy.
4. Flexibility of structure.
   (4 marks)

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Describe three types of operations commonly performed on file directories.

1. Creating directories.
2. Deleting directories.
3. Renaming directories.
   (6 marks)

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Differentiate between demand cleaning and pre-cleaning as used in virtual memory management.

1. Demand Cleaning: Pages are cleaned when they are required for new data.
2. Pre-cleaning: Pages are cleaned in advance, before they are needed.
   (4 marks)

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Describe the process of reading a block of data from a device using the DMA I/O technique.

1. CPU initializes the DMA controller with the source and destination addresses and the data count.
2. DMA controller takes over the data transfer from the device to memory.
3. Upon completion, the DMA controller interrupts the CPU to indicate the transfer is done.
   (6 marks)

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(a) Explain the term “head” as used in disk systems.
The head is the part of a disk drive that reads and writes data.
(2 marks)

(b) Explain the term “density” as used in disk systems.
Density refers to the amount of data that can be stored in a given area of the disk.
(2 marks)

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(a) Explain two types of indexes that could be applied in an index-sequential file organization system.

1. Primary Index: Indexes based on primary key.
2. Secondary Index: Indexes based on non-primary key attributes.
   (4 marks)

 (b) Outline two application areas where the index-sequential file organization system is most appropriate.

1. Databases.
2. File systems requiring fast access to records.
   (2 marks)

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(a) Identify the condition depicted in the figure and justify your answer.
(2 marks)

(b) Explain three measures that could have prevented the condition.
(6 marks)

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(a) Distinguish between a clock interrupt and an I/O interrupt as used in process management.

1. Clock Interrupt: A signal sent at regular intervals to manage system time and process scheduling.
2. I/O Interrupt: A signal indicating that an I/O operation has completed, prompting the CPU to process the data.
   (4 marks)

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(a) Explain the principle of locality as used in memory management.
Programs tend to access a relatively small portion of their address space at any given time.
(2 marks)

(b) Outline four typical contents of a page frame data table as applied in memory management systems.

1. Page frame number.
2. Status bits.
3. Reference count.
4. Modified bit.
   (4 marks)

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For each of the following disk scheduling algorithms, determine the average seek length assuming that the starting track is 100:

(a) FIFO:
(3 marks)

(b) SSTF:
(3 marks)

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Describe the contiguous file allocation method with the aid of a diagram.
(4 marks)

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(a) Explain the term “virtual address” as used in memory management.
A virtual address is an address used by programs to access memory, which is then translated to a physical address by the system.
(2 marks)

(b) Explain the term “thrashing” as used in memory management.
Thrashing is a condition where excessive paging operations reduce the overall performance of the system.
(2 marks)

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Describe a typical organization of an I/O subsystem with the aid of a diagram.
(7 marks)

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Outline three lists that are maintained to manage the buffer cache in UNIX systems.

1. Free list.
2. Dirty list.
3. LRU (Least Recently Used) list.
   (3 marks)

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Explain three techniques applied by operating systems to manage space on disks.

1. Bitmaps: Use of bitmaps to track free and allocated space.
2. Linked Lists: Use of linked lists to manage free blocks.
3. Free-space Grouping: Grouping free blocks together.
   (6 marks)

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Differentiate between best-fit and first-fit policies as used in memory management.

1. Best-fit: Allocates the smallest available block that fits the requested size.
2. First-fit: Allocates the first available block that is large enough.
   (4 marks)

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Outline two categories of user access rights used in file management.

1. Read: Permission to read the file.
2. Write: Permission to modify the file.
   (2 marks)

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Outline four requirements for an interactive and networked environment that a file management system should satisfy.

1. Security: Protecting files from unauthorized access.
2. Concurrency: Managing access by multiple users.
3. Recovery: Ensuring data

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