1.2.1 Systems Software Exam Questions
Paper 1 · Computer Systems · 10 past paper questions · 39 marks
Exam questions for 1.2.1 Systems software
10 OCR past paper questions (39 marks) with mark schemes
Answer each question, reveal the mark scheme, then award yourself marks. Scores and answers are saved in this browser so you can see which topics need more work.
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- Question 1H446/01 · June 20241 mark
Application software is run on thin client computers. A thin client computer is a very low-powered computer connected to a powerful central server. The operating system and all the applications run within a virtual machine on the server. The thin client computer will only display the output of the virtual machine and capture and send input to the virtual machine. State one advantage of running the application software within the virtual machine.
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Reduced hardware is needed on computers // reduced hardware costs Improved security by keeping all software running from one physical device Easier/cheaper to manage as only one physical device runs the programs Can add/remove resources/memory/processes to the VM If it is infected by malware it can be deleted and recreated // the rest of the system isn't affected/is protected against malware No direct access to hardware Resources can be used more flexibly between the machines (1 mark)Mark yourself: how many marks did you get?/ 1 - Question 2H446/01 · June 20244 marks
Two roles of an operating system are to handle interrupts and manage scheduling. Describe two other roles of an operating system.
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Resource/memory management e.g. Moving data between RAM and secondary storage/ virtual memory // paging and/or segmentation // Allocating/deallocating memory Manage hardware/peripherals e.g. Tracking all devices connected to the system // Device drivers File management e.g. Storing files in secondary storage // Searching for //copying // moving // renaming files/folders Security/user management e.g. Controlling who can access the system //Managing user profiles // Controlling who can access certain resources on the system // Managing access rights Provide a user interface e.g. Allowing the user to interact with the software/hardware/computer Providing utilities e.g. Used to monitor // manage // maintain the computer // To manage the security // Providing a platform on which to run software (4 marks - 2 marks per role with description)Mark yourself: how many marks did you get?/ 4 - Question 3H446/01 · June 20245 marks
Draw a line to match each scheduling algorithm to the correct description. The descriptions are not in the same order as the algorithms.
Scheduling algorithm Description Round Robin Splits processes into different priority queues based on the amount of processor time they need. It allows them to move between the queues as their characteristics change First come first served Selects the process that takes the shortest amount of time to complete. The processes are run until they are fully complete Multi-level feedback queues Each process is allocated a fixed amount of CPU time. If the process is not complete it will be suspended and the next process will start Shortest job first Each process is given equal priority and they are processed in the order they arrive Shortest remaining time Selects the process that takes the shortest amount of time. The process can be suspended if another shorter process is added Show mark scheme
Round Robin - Each process is allocated a fixed amount of CPU time. If the process is not complete it will be suspended and the next process will start First come first served - Each process is given equal priority and they are processed in the order they arrive Multi-level feedback queues - Splits processes into different priority queues based on the amount of processor time they need. It allows them to move between the queues as their characteristics change Shortest job first - Selects the process that takes the shortest amount of time to complete. The processes are run until they are fully complete Shortest remaining time - Selects the process that takes the shortest amount of time. The process can be suspended if another shorter process is added (5 marks - 1 per correct match)Mark yourself: how many marks did you get?/ 5 - Question 4H446/012 marks
A secondary school is upgrading their computers. They decide to install 'thin client' computers. A thin client computer is when users access their computer in the usual way with a keyboard, mouse and monitor. However, all processing takes place on the virtual machine on a server rather than the computer at their desk. Describe one advantage of using virtual machines in this way.
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Allows for more efficient use of computing resources ... Less likely to have workstations run idle ... can allocate more resources to power users dynamically Or Thin clients are cheaper than desktops... which could save the school money Or Thin clients are often physically smaller than desktops... allowing more desk space/workspace for staff/students (2 marks - 1 for reason, 1 for expansion)Mark yourself: how many marks did you get?/ 2 - Question 5H446/012 marks
Describe one disadvantage of using virtual machines in this way.
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Can cause network overload... if the network does not have sufficiently good bandwidth Could create process lag... If lots of large processes run at the same time If a virtual machine hangs/crashes the user is unable to reset it... whereas they can physically reboot on a local machine Thin-clients may not be compatible with some peripherals... meaning some of the school's peripherals become unusable (2 marks - 1 for disadvantage, 1 for expansion)Mark yourself: how many marks did you get?/ 2 - Question 6H446/016 marks
Each virtual machine will run an operating system. One type of operating system is multi-user. Describe two other types of operating system and give an example of where each may be used.
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Multi Tasking - is optimised to deal with multiple processes simultaneously/concurrently ...Can run multiple programs/tasks at the same time. Example: Home/personal computer Distributed - Designed to run the same task over multiple machines. Example: SETI or other cloud-based processes// Clusters of desktops used for rendering/calculations Embedded - Will have a restricted set of operations (to conserve resources) ... is read only. Example: Domestic appliance such as a washing machine Real-Time - optimised to handle and respond to inputs with no wait/within a guaranteed response time/immediate. Example: Used in "mission critical" systems such as aircraft control (6 marks - 1 mark for type, 1 for description, 1 for example per OS, max 6)Mark yourself: how many marks did you get?/ 6 - Question 7H446/01 · June 20231 mark
A small manufacturing business uses networked computers with closed source application software installed. One computer owned by the business monitors critical-safety features of manufacturing. All input data must be processed within a predictable timescale of a fraction of a second. State the type of operating system that should be used by this computer.
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Real time (1 mark)Mark yourself: how many marks did you get?/ 1 - Question 8H446/01 · June 20236 marks
Give the name of three other types of operating system, and for each state its purpose.
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Multi-tasking … runs multiple programs at the same time Multi-user … allows multiple users at the same time Distributed … allows multiple computers to work together on a single task Embedded … has a dedicated/limited function …is read-only / cannot be changed (6 marks - mark in pairs: 1 for type, 1 for purpose per OS)Mark yourself: how many marks did you get?/ 6 - Question 9H446/01 · June 20233 marks
When a device such as a keyboard or printer requires attention from the CPU, an interrupt is raised. Explain how an operating system deals with an interrupt.
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Interrupt checked for at start/end of each fetch-execute cycle If the interrupt is of a lower/equal priority to the current process then the current process continues (If interrupt raised) contents of registers copied to stack Flags are set to determine if interrupts are enabled / disabled Program counter changed to point to Interrupt Service Routine (ISR) // ISR runs After interrupt complete, previous register values restored back from stack Flag is reset If higher priority interrupt received during servicing of interrupt… this is added to stack and new interrupt dealt with (3 marks - 1 per bullet, max 3)Mark yourself: how many marks did you get?/ 3 - Question 10H446/01 · June 20239 marks
Memory management is a key function of an operating system. Explain how an operating system can manage the memory available to applications and why doing so is important. You should include the following in your answer: the different actions carried out by an operating system to manage memory, how memory that is being managed can be split up, why memory management is important.
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Levels of response question (9 marks) AO1: Memory management means to ensure that RAM is used efficiently and not wasted. Removes data not needed anymore (garbage collection), frees up space and allocates memory to applications. Paging or segmentation may be used to split up memory. Paging uses fixed size divisions whereas segmentation uses varying size divisions. Paging is where memory is divided physically. Segmentation is where memory is divided logically. Virtual memory may be used when RAM is (almost)full to enable applications to continue to run. AO2: If RAM is unavailable or full, applications cannot be loaded. Data transferred out of RAM into virtual memory to free up space and then transferred back again when needed. Also includes security so that data stored in memory is not vulnerable. Memory management is important for a well-running machine. If not, RAM would rapidly run out and fill up with unneeded data/instructions and so no new applications could run. Paging causes internal fragmentation whereas segmentation causes external fragmentation. A page table is used to map page location which is slower than a segmentation table. It is easier for the OS to manage page locations as they can be stored non-contiguously. AO3: RAM is much more expensive than secondary storage (per unit/GB) so virtual memory is useful rather than having to buy more RAM. Over use of virtual memory causes slow down and even disk thrashing if pages have to be swapped back and forth too often. Paging can be more effective because any free memory space can be used to swap data in and out whereas with segments, lots of space will sit unused until a segment the right size is available. Segmentation errors can cause memory leakage which would cause the system to crash. Security issues – applications can only access memory allocated to them.Mark yourself: how many marks did you get?/ 9
- 1Scheduling algorithms: Round Robin (time slice), FCFS (arrival order), SJF (shortest first), SRT (preemptive)
- 2BIOS functions: POST (hardware check), bootstrapping (load OS), settings in CMOS
- 3Interrupts: Signal → Save state → Execute ISR → Restore state → Resume
- 4Virtual memory: Uses disk as RAM extension; Thrashing = excessive paging → add more RAM
- 5Paging vs Segmentation: Fixed-size blocks vs Variable-size logical divisions
- •Practice answering questions under timed conditions
- •Check your answers against the mark scheme carefully
- •Focus on understanding the marking points, not just memorising answers
- •Review past paper questions from multiple years to spot patterns