[Unit 1.2.1] Systems Software Flashcards by Oliver Ashford

what is application software

allows user to do or make something

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what is system software

program designed to run hardware and application program

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what is operating system

controls hardware and software resources

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what are the three types of systems software

OS, device drivers, utilities

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what are device drivers

tells OS how to interact with peripherals

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what are utilities in terms of systems software

housekeeping and maintenance programs

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what are the 7 key features of the OS

processor scheduling (order processes executed)
handling interrupts (dealing w requests disrupting CPU)
memory management (memory allocated efficiently)
file management (tracking files in 2nd storage)
device management (efficient coms w I/O devices)
providing security (resources protected from unauthorised users)
provide UI

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what are the four types of UI

CLI
GUI
menu based
natural language

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what is a command line interface. what are the advantages and disadvantages

type commands.
not intuitive (for experts)
uses less memory

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what is a GUI. what are the advantages and disadvantages

windows, icons, menus, pointer (WIMP)
intuitive (for non-experts)
uses more system resources

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what is a menu based UI. what are the advantages and disadvantages. give an example

limited options (like ATM)
for people who have no clue how to use technology
have limited functionality

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what is a natural language UI. what are the advantages and disadvantages

uses voice recognition.
it is very intuitive
not always completely accurate

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what is the kernel in terms of OS

it is the core of the OS, it has complete control over everything in the system. It is the first part of the OS to load after the bootloader

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what are the five types of OS

multi tasking
multi user
embedded
real time (RTOS)
distributed

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what is the multi tasking OS

multiple programs at same time
works due to speed of CPU
has process manager and memory manager

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what is the multi user OS

multiple users can use a system at same time
controls resource consumption so users dont affect each other

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what is the distributed OS

multiple computers work together on a single task
controls and coordinates many computers
presented as if it is one system

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what are the uses of a distributed OS

working on scientific problems
rendering CGI effects

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what is the embedded OS

on devices that have limited functions
for hardware reliability
efficient use of resources
OS stored on ROM as unchangeable

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what are some things that would use an embedded OS

smart tvs
ATMs
washing machines
smart watches
elevators

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what is the real-time OS

designed for performing actions in guaranteed time
must be reliable, precise and consistent
used for safety critical systems
-self driving cars or autopilot
used in embedded systems
-medical systems (MRI)
-car engine management

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what is the role of memory management

control allocation of RAM to each process
stop programs interfering with each other
allow multitasking
allow programs to use virtual memory

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how is memory allocated

when there is free space that is fragmented it is easier to split up the program
do this by:
-segmentation
-paging

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how does segmentation work

split into segments though logical divisions
-complete sections of programs
they are not fixed size

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how does paging work

divided into pages through physical divisions -a module may be split into two they are a fixed size

define "process scheduling"

process manager removing running processes and choosing another process based on a strategy

what are the role of the process manager

complete as many tasks as possible in least time ensure no task left for too long make efficient use of CPU time minimise delay in request and completion

what are the 5 types of scheduling algorithms

first come first served round robin shortest job first shortest remaining time multi level feedback queues

how does first come first served work

processes run from start to finish in order of arrival

what are the advantages of first come first served

simplest to implement once started running it will be done in minimal time good with few concurrent tasks

what are the disadvantages of first come first served

prevents processes running till current done doesn't consider size or priority important tasks could get stuck at back of queue

how does round robin work

each process given fixed time slice if it doesn't finish in that time it is sent to back of the queue

what are the advantages of round robin

simple to implement good if all tasks about same size and priority

what are the disadvantages of round robin

doesn't look at size or priority

how does shortest job first work

chooses shortest task and runs till completion

what are the advantages of shortest job first

max jobs completed short jobs dont wait for longer tasks using all CPU time

define "starvation" in terms of CPU time

being constantly denied processor time. being unable to run/complete

what are the disadvantages of shortest job first

estimates time taken (could be wrong) longer tasks could be starved doesn't look at priority

how does shortest remaining time work

process with least time left runs if shorter one comes, current one is suspended

what are the advantages of of shortest remaining time

short processes handled quickly max jobs completed

what are the disadvantages of shortest remaining time

longer tasks starved doesn't look at priority

how does multi level feedback queues work

have queues of different priority levels when new jobs arrives it's placed in relevant queue. can move processes between queues: -dependant on new information -or if job waited for too long

what are the advantages of multi level feedback queues

takes into account priority high priority task run on time

what are the disadvantages of multi level feedback queues

complex implementation not good if processes have similar priority low priority tasks could be starved.

what are two ways of dealing with events that require immediate attention

polling interrupts

how does polling work

checks each software/hardware to see if it needs attention inefficient and waste of time

how do interrupts work

signal from software/hardware tell CPU that it requires immediate attention

what are the two types of interrupts

hardware (mouse click etc) and software (app closed etc)

what is an interrupt service routine

code designed to handle interruptions

when does the ISR check for interruptions

at the end of each FDE cycle

what happens when an interrupt occurs

priority checked registers values copied into stack origin identified so correct ISR called ISR address loaded into PC ISR executed previous task restored and resumed

what happens when a higher priority interrupt comes along

current interrupt is added to stack new interrupt is serviced

what are two problems with interrupts

latency - hard to code program that handles interrupts on time Stack overflow - crashes computer

what are device drivers

program controls operation of peripheral enabling OS to control and communicate with them

what are the disadvantages of using a generic device driver

missing features inefficient

what is the BIOS

allows OS to be loaded from power on.

where is BIOS stored

non volatile flash memory

what is the purpose of BIOS

perform POST bootloader loads OS kernel into memory

what is a virtual machine

program that works like a separate computer inside the main

what is a hypervisor in terms of virtual machines

program controlling the VM

what is the host in terms of virtual machines

computer running the VM

what is the role of the hypervisor in terms of virtual machines

controls how VM can access resources on the host.

what are the advantages of virtual machines

run old applications run multiple OS easy to back up can be deleted and reinstalled (protect from malware)

what are the disadvantages of virtual machines

programs can run slower software must still be licensed