Unit 1.2.1 Systems Software Flashcards

Question

Why would moving program D to make space for Program E be inefficient?

Answer 1

- There is enough total free space available – it's just not located together in a single block. - But it takes a lot of time to move a program in memory or on disk, as addresses and free space references all need updating.

Answer 2

- Paging - Segmentation

Answer 3

- Physical divisions of the memory into fixed lengths of sections (pages) - They are made to fit sections of memory. - Programs are split up to fit into a given number of pages.

Answer 4

- Dividing memory into segments of complete sections of code. - Segments are logical divisions.

Answer 5

- Both allow programs to run despite inefficient memory - Pages and segments are stored on disk - Pages and segments are separated into segments when needed.

Answer 6

- Pages are fixed sizes and segments are at variable length. - Pages are made to fit sections of memory, and segments are complete segments of programs - Pages are physical divisions but segments are logical divisions

Answer 7

- Paging takes no account of how it splits the program into fixed-sized pages. - It could separate the instructions inside a looping condition so they are in different pages which would be inefficient. - It would be better to keep those instructions together in memory.

Answer 8

- Efficient use of memory (reduces wasted space and simplifies memory management) - Protection and security (each page assigned its own protection level) - Reduced fragmentation (allocating memory in more organized manner) - Flexibility and Scalability (allows OS to allocate memory resources to different processes efficiently when computer demands change) - Virtual memory

Answer 9

- Overhead and latency (OS must constantly monitor and manage paging system) - Increased fragmentation on the hard drive - Adds a layer of complexity, so it's harder to understand and troubleshoot + hardware determined size of page - Memory thrashing (when OS constantly switches pages in and out of memory) - Sensitive data may be stored on hard drive and vulnerable to malware software/system attackers.

Answer 10

- No internal fragmentation - Improves CPU utilization - Allows for sharing memory segments between processes - User can determine segment size and their perception of physical memory is similar to segmentation - Segments can be of variable sizes and processes can have multiple segments

Answer 11

- Increased fragmentation on the hardware - Overhead and reduced performance - More complex to implement and manage than paging.

Answer 12

A signal emitted from hardware or software when a process or an event needs immediate action, serving as a request for the CPU to it suspend what it is doing and run the process associated with the interrupt.

Answer 13

- Decreases the waiting time of CPU - Stops the wastage of instruction cycle - Enables multitasking by allowing the CPU to quickly switch between different processes - Simplifies input/output (I/O) operations by allowing devices to communicate directly with the CPU.

Answer 14

The processor needs to stop executing its current program to run the code for the interrupt (the ISR)

Answer 15

A program with a set of instructions that need to be fetched, decoded and executed to carry out the operations of the interrupt.

Answer 16

Interrupts always have a higher priorities than normal programs.

Answer 17

- Hardware - Software - User - I/O device - Timer

Answer 18

- Power supply failure - Power/reset button pressed / Power-down command - Memory parity error - Internal clock triggers suspending a running process

Answer 19

- Illegal instruction encountered in interpreted code - Arithmetic overflow - New log-on request

Answer 20

- Moving the mouse - Typing the keyboard - Clicking/tapping an icon to open a new program

Answer 21

- Buffer nearly empty - Signals the completion of a data transfer to or from a device - Printer ink supply notification

Answer 22

- Data-logging program reading an input sensor every second - Screen recording application

Answer 23

Within a computer system, electrical or magnetic interference from internal or external causes can cause a single bit of memory to spontaneously flip to the opposite state. This event makes the original data bits invalid.

Answer 24

A region of a memory used to store data temporarily while it is being moved from one place to another.

Answer 25

The result of a calculation that exceeds the memory space designated to hold it.

Answer 26

1. If the process is of a lower/equal priority of the current process then the current process continues. 2. If it is of a higher priority, the CPU finishes the current CPU cycle. 3. The contents of the CPU registers are copied to a stack in memory. 4. The relevant ISR is loading by changing the value in the program counter to the address of the first instruction of the interrupt. 5. When the ISR is complete, the previous contents are popped from the stack and loaded back into the registers.

Answer 27

So that the CPU always has one process to execute - reducing the CPU's idle time and increase its utilization.

Answer 28

- Maximize CPU utilization - Fair allocation of CPU time to every process - Increase throughput - Reduce the turnaround time ( the time taken to complete a process or fulfill a request) - Reduce the waiting time and response time

Answer 29

- Which process to execute next - The length of time the next process can execute for

Answer 30

- First Come First Serve - Shortest job first - Round Robin - Shortest Time Remaining - Multi-level Feedback Queue

Answer 31

- The processes in the ready queue are executed in the order of arrival. - The first to enter the ready queue is first to enter the running state. - Not pre-emptive

Answer 32

+ Simple and easy to understand + Gives processes equal opportunities + Guarantees all process eventually enter the running state + Low scheduling over head + Well suited for long process / workloads without strict time constraints

Answer 33

- Waiting time often too long - Favours CPU Bound process than I/O Bound Process - Convoy effect (other processes can only enter running state when current execution is finished) - Lower CPU and device utilization (because of convoy effect) - Troublesome for multiprogramming systems - If the first process has a long execution time, it results in more waiting time

Answer 34

- Processes that are estimated to have the shortest execution time are run first until they are complete - Not pre-emptive

Answer 35

+ Shortest jobs are favoured + Probably optimal for minimizing waiting time of the processes

Answer 36

- May cause starvation of longer processes (solves by aging) - Can't be implemented at level of short-term CPU scheduling

Answer 37

- Processor time is divided in equal time slices for processes in the running state - If the process in the running state hasn't finished when this processor time is up, it is set to the back of the ready queue - Pre-emptive

Answer 38

+ Each process gets an equal share of the CPU's processing time + Cyclical in nature, so there is no starvation

Answer 39

- Setting quantum too short increases overhead and lowers CPU efficiency - Setting quantum too long can cause a poor response to short processes - Average waiting time under RR policy is often too long - If time quantum is very high RR degrades to FCFS

Answer 40

- Processes that are estimated to have the shortest execution time are moved to the running state although they may return the ready queue before completion if a shorter job arrives. - Pre-emptive

Answer 41

+ Reduces number of preemptions and context switches as processes with shorter predicted completion times are given higher priority + Short processes return quickly and has a high yield of processes executed in a given time

Answer 42

- Involves more overheads that SJF - Long processes may always be left in starvation if small processes are continuously added - inaccurate predictions can lead to poor scheduling decisions

Answer 43

- Several ready queues are added, each with a different scheduling algorithm - Processes are able to move between queues as priorities change - Preemptive

Answer 44

+ More flexible than MLQ as it allows different processes to move based on their behaviour and needs + Prevents starvation by moving a process that is waiting too long for the lower priority queue to the higher priority queue.

Answer 45

- The most complex algorithm because of the flexibility and overheads - Produces more CPU overheads than MLQ - Selection of best scheduler requires some other means to select the values

Answer 46

Changing the processes with lower priority from the running state to the suspended state to be put back into the ready queue to allow processes with high priority to be executed.

Answer 47

- Multi-tasking - Multi-user - Distributed - Embedded - Realtime

Answer 48

- A logical extension of a multiprogramming operating system, where users can run multiple programs and tasks simultaneously. - Without losing data, the operating system keeps track of each job and allows you to switch between jobs without allowing the data to be lost.

Answer 49

- Most operating systems allow more than one person to use a computer at the same time. - The computer will manage the user's various permissions and access rights when they log on. - Server operating system software will handle requests of multiple people using different computers on a network at the same time.

Answer 50

- Separate computers can be joined together via network connections to work together and the data and instructions that need to be processed is split between each node (computer) in the system. - It controls and coordinates the communication between the computer nodes and presents them to the user as if they were a single system.

Answer 51

An OS which can perform repeated tasks within a tight time boundary. Plenty of redundancy is built into these systems so they can handle sudden increases in input. As such, processors in real-time operating systems rarely run at capacity.

Answer 52

A specialized operating system (OS) designed to perform a specific task for an embedded system (e.g. washing machine). The main job of an embedded OS is to run the code that allows the device to achieve a specific task.

Answer 53

- In single-processor systems, each active program is scheduled to receive a tiny time slice in quick rotation, giving the impression they are operating at the same time. - Even modern processors with multiple cores still need to handle many processes at the same time.

Answer 54

Can be useful to combine the processing power of multiple computers across a network for a single processor-intensive task. Online shopping also use this operating system - your basket might be handled by one server while the querying of items is handled by another. As the system becomes busy with more user requests, additional servers might automatically join the system, load-blanching requests transparently.

Answer 55

In safety-critical environments such as aircraft autopilot systems, hospital monitoring machines, self-drive cars and missile systems, processes have to be guaranteed to execute within a known time frame. They are designed to run critical applications reliably and with precise timing (paying attention to the programmer's priorities).

Answer 56

Processors exist in an almost limitless list of devices (e.g. washing machines, set-top boxes, TVs etc). Embedded operating systems tend to run on dedicated hardware so they run with maximum efficiency, using low-powered processors and very little memory.

Answer 57

- The basic input-output system performs hardware initialisation when the computer is turned on - Determines which drive to boot the operating system from, amongst other things. - These instructions don’t change, so they could be stored in ROM. - But the settings chosen by the user need to be read-and-write, stored in non-volatile memory (CMOS with a battery)

Answer 58

- Power-on self-test - Handled by the BIOS, the power-on self-test checks the hardware is installed correctly before loading the operating system

Answer 59

- The program that loads the operating system - The BIOS tells the bootstrap which drive to load the operating system from.

Answer 60

- The central component of an operating system - A bridge between applications and data processing performed by the hardware - The kernel's responsibilities are to manage the system resources (e.g., processor, memory, peripherals, etc)

Answer 61

A small piece of software that tells the operating system how to communicate with a piece of hardware. It provides an interface between the device and operating system,

Answer 62

- They act as translators between a hardware device and the applications or operating systems that use it - They enable your PC’s operating system and applications to communicate with all of your hardware - Without them, the OS cannot communicate with the hardware, and therefore the hardware won’t function - The computer must be able to output to a wide range of devices.

Answer 63

It translates the operating system's instructions to produce an output (e.g. print a document) into a series of instructions that a specific piece of hardware will understand.

Answer 64

- Printer driver - Video driver - I/O driver - USB driver.

Answer 65

A program that allows your computer to mimic the behaviour of another hardware device. It enables you to run software by tricking it into thinking its running on its native hardware instead of an entirely different machine.

Answer 66

- Building/deploying apps to the cloud - Trying out a new OS / backing up your existing OS - Accessing virus-infected data / testing out anti-virus software - Making a new environment to allow developers to run dev-test scenarios - Creating a PC game (using an emulator to stimulate another device)

Answer 67

The process of creating a software-based (or virtualised) version of a computer with dedicated amounts of CPU, memory and storage borrowed from the host computer.

Answer 68

- A server that runs on a virtual machine rather than on a physical computer. - Virtualization software allows a single physical server to be partitioned into multiple virtual servers, each with its own operating system and applications. - This allows multiple users to share the same physical server while maintaining their own isolated environments.

Answer 69

In a virtual server environment, a number of servers could run an application. So if one server fails, the application can automatically be run by another server. This way, no technical support is necessary and there is no down-time.

Answer 70

It is designed to run on many different platforms because it compiles its code into intermediate code (Java Bytecode). The Bytecode is then translated by a Java Virtual Machine running on a target device - translating into specific machine code.

Answer 71

A set of general instructions is translated (from intermediate code) into a variety of processor types before execution by a Java Virtual Machine. The JVM converts each generalised machine instruction into a specific machine instruction that the computer's specific hardware will understand.

Answer 72

- Reducing need for hardware (reducing cost) - Can be replicated in minutes - Idependent and portable - Multiple operating systems can coexist - Provides isolation between guest OS and server, making it more secure

Answer 73

- Less efficient than real machines and the host computer - High cost of implementation - Security risks - Running multiple VMs on one machine leads to unstable performance - Complex systems needing technical skills and maintenance

Unit 1.2.1 Systems Software Flashcards

(97 cards)