Module I — Operating Systems — Nov/Dec 2025

Module I • Level not stated • November/December 2025 • Written assessment

Work through each question before checking the answer. These revision answers are prepared for learners; they are not an official marking scheme.

Question 1

Identify the resource-sharing technique shown and state three limitations.

Answer

Threads wait on and release a semaphore controlling shared resources.
Threads wait on and release a semaphore controlling shared resources.

The diagram shows semaphore-based synchronisation.

  • Incorrect wait/release order can lead to deadlock.
  • An unfair scheduling policy can leave a thread starving indefinitely.
  • Priority inversion can occur when a high-priority thread waits for a resource held by a lower-priority thread.

Question 2

Give four characteristics of a microkernel.

Answer

  • Keeps a small set of essential functions, such as scheduling, address-space management and IPC, in kernel mode.
  • Many services, such as drivers or file servers, run as separate user-space processes.
  • Services communicate through message passing.
  • Isolation improves fault containment and modularity, though message/context-switch overhead can affect performance.

Question 3

State two ways to update Windows.

Answer

  • Use Settings → Windows Update to check for and install supported updates.
  • Install an applicable official Microsoft Update Catalog package or use the organisation’s managed update service.

Question 4

Illustrate four stages in a process lifecycle.

Answer

New → Ready → Running → Terminated; Running can block for I/O and return to Ready when the event completes.
New → Ready → Running → Terminated; Running can block for I/O and return to Ready when the event completes.
  • New: the OS creates the process and its control structures.
  • Ready: it can run but is waiting for a CPU allocation.
  • Running: its instructions execute on a processor.
  • Terminated: it finishes or is stopped and its resources are reclaimed. The full common model also includes Waiting/Blocked.

Question 5

Give three results of shrinking a disk volume.

Answer

  • The selected volume becomes smaller.
  • Unallocated space is created after the volume where the shrink operation permits.
  • That space can be used for another volume or a suitable extension; shrinking does not automatically create or format a new partition. Unmovable data can limit the shrink size.

Question 6

Describe four steps for creating an Excel chart.

Answer

  1. Arrange data with meaningful headings in a range.
  2. Select the headings and data.
  3. Use Insert and choose a suitable chart type.
  4. Check the data series and add a clear title, axis labels/units and legend; adjust the layout.

Question 7

Give four measures for protecting files after a data breach.

Answer

  • Restrict file access with least-privilege user/group permissions.
  • Use strong authentication and multifactor authentication for accounts that support it.
  • Encrypt sensitive stored files and protect the encryption keys.
  • Maintain protected backups and audit access logs to detect unauthorised use.

Question 8

Identify the I/O management technique and name four device examples it supports.

Answer

OS buffers hold incoming device data before it moves to a consuming user process.
OS buffers hold incoming device data before it moves to a consuming user process.

Buffering temporarily holds data to accommodate differences in producer and consumer speed.

  • Keyboard input.
  • Disk or SSD data transfers.
  • Network-interface receive/transmit operations.
  • Audio input/output streams.

Question 9

Define BCC and spam in email.

Answer

  • BCC (blind carbon copy) sends a copy to recipients whose addresses are not shown to other recipients in that message.
  • Spam is unsolicited bulk or unwanted messaging, commonly including advertising or fraudulent messages.

Question 10

Give a four-step graphics-driver update procedure.

Answer

  1. Identify the GPU, Windows version and architecture.
  2. Find a compatible signed driver through the computer/GPU manufacturer’s official support channel or Windows Update.
  3. Install the approved update using the provided installer or Device Manager’s update procedure.
  4. Restart if required and verify the driver version and graphics application; retain a rollback option if problems appear.

Question 11

Give four properties of client-server OS structure.

Answer

  • Clients request services from separate server processes.
  • Communication uses defined IPC/message interfaces.
  • Services such as file management can be separated from the kernel and from one another.
  • The modular separation supports maintenance and fault isolation; it can also be extended to remote services where designed.

Question 12

Identify three formatting features in the extract, explain three deadlock-prevention measures, and give four SSD advantages.

Answer

Document extract showing an enlarged drop cap, yellow highlighting and a border.
Document extract showing an enlarged drop cap, yellow highlighting and a border.
  • Drop cap: the enlarged initial D spans several lines.
  • Text highlighting: selected sentences have a yellow background.
  • Border: a rectangular line encloses the paragraph.
  • Prevent hold-and-wait: require a process to obtain all needed resources together or release held resources before requesting more.
  • Break circular wait: impose a consistent global order for acquiring resources.
  • Allow preemption where the resource permits it: reclaim/retry a held resource when another required resource cannot be obtained.
  • Fast random access with no mechanical seek delay.
  • Better resistance to shock because there are no moving read/write heads.
  • Lower operating noise.
  • Often lower energy consumption and smaller physical size. SSDs do not make every HDD application obsolete; cost, capacity and workload still matter.

Question 13

Using the given processes, construct FCFS, SJF, priority and round-robin (quantum 3) schedules. Then explain three PowerPoint views and three OS types.

Answer

Process Arrival Burst Priority
P0 0 6 1
P1 1 4 2
P2 2 9 1
P3 3 7 3

Use non-preemptive SJF and priority; lower priority number means higher priority, and equal priorities use arrival order. The printed “service time” column is inconsistent with these arrivals/bursts; compute start times from the data above. For round robin, arrivals at a quantum boundary enter before the running process is requeued.

Algorithm Execution intervals
FCFS P0: 0–6; P1: 6–10; P2: 10–19; P3: 19–26
SJF P0: 0–6; P1: 6–10; P3: 10–17; P2: 17–26
Priority P0: 0–6; P2: 6–15; P1: 15–19; P3: 19–26
Round robin, q=3 P0: 0–3; P1: 3–6; P2: 6–9; P3: 9–12; P0: 12–15; P1: 15–16; P2: 16–19; P3: 19–22; P2: 22–25; P3: 25–26
Gantt charts for FCFS, SJF, priority and quantum-three round robin using the four supplied processes.
Gantt charts for FCFS, SJF, priority and quantum-three round robin using the four supplied processes.
  • Normal view: create and edit slides and notes.
  • Slide Sorter: review the deck as thumbnails and rearrange slides.
  • Slide Show: present the slides full screen.
  • Batch OS: executes queued jobs with little interactive intervention.
  • Time-sharing/multitasking OS: shares processor time among active tasks/users.
  • Real-time OS: schedules work to meet specified timing deadlines.

Question 14

Describe three file access methods, three reasons for renaming a file, and swapping with two round-robin processes.

Answer

  • Sequential: read or write records in order from the current position.
  • Direct/random: jump to a specified offset or record.
  • Indexed: use an index to locate the required record or block.
  • Resolve a duplicate-name conflict when saving or copying into the same directory.
  • Remove invalid characters or comply with file-system/path naming limits.
  • Give a meaningful name or correct a mistaken name; changing an extension alone does not convert a file format.
P1 and P2 alternate residency/CPU use; a suspended process can be written to backing storage and restored to memory.
P1 and P2 alternate residency/CPU use; a suspended process can be written to backing storage and restored to memory.

Swapping saves a suspended process’s memory image to backing storage and restores it when needed. If P1 is swapped out to make room for P2, retain P1’s process state and address-space information; later restore P1 before dispatching it. Round robin does not require a disk swap at every quantum: when both processes fit in RAM, normal context switching is sufficient.

Question 15

Describe four Office file formats, four process/thread differences, and HDD parts 5 and 7.

Answer

  • DOCX: editable Word document containing formatted text, tables and related content.
  • XLSX: Excel workbook containing worksheets, data, formulas and charts.
  • PPTX: editable PowerPoint presentation containing slides.
  • ACCDB: Access database containing tables, queries, forms and reports.
Aspect Process Thread
Address space Typically has its own protected address space Shares its process address space with sibling threads
Resources Owns resources such as handles and memory mappings Shares many process resources but has its own stack and registers
Creation/switching Usually more expensive Usually less overhead within one process
Communication/isolation Uses IPC; one process can often fail without corrupting another Shared memory simplifies communication but requires synchronisation
HDD diagram with label 5 pointing to the read/write head near the platter and 7 to the circuit board underneath.
HDD diagram with label 5 pointing to the read/write head near the platter and 7 to the circuit board underneath.
  • 5 — Read/write head: reads and writes magnetic information on the platter; the arm positions it over the selected track.
  • 7 — Controller/circuit board: controls the drive electronics, motor and data interface, and coordinates transfers with the host.
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