0.8 and 0.9

System software allows control over the hardware and software of the computer; essential in order to perform even the most basic tasks

Application software is software that allows a user to carry out a specific task

All software make use of theOSinordertoperform basic tasks such as saving files.

Application

Operating system

Hardware devices

Hardware

The OS is responsible for managing the computer’s resources;

Hardware drivers are simply software that understands how to talk directly to a given piece of hardware.

–Drivers are normally produced by the manufacturer of the hardware, but can be produced by OS or open source community.

Hardwareandsoftware can trigger interrupts and these are then dealt with by calling an interrupt service routine.

Information about files is stored in an index known as the file allocation table (FAT)

Block journaling will store the data to be saved in the journal before committing it to hard drive.

FAT - will store the location of all files on the hard drive and store metadata about the file.

Designed to perform a commonplace task eg transferring data from one storage device to another.

• Filemanaging utility – file management enables user to do simple file manipulations
  • Alone itaccomplishes very little.
  • Cannot openfiles,asthat is the responsibility of the program

• Compression software – used to compress files to reduce their overall size
  • Closest to minimum size without losing any data.
  • When it becomes compresses it is unreadable until it is decompressed by the original utility software

• Task managers – allow the user to view the processes currently running on a system and see what resoruces each is utilising.
  • Helpful withbottleneckissues
  • Killing unresponsive processes

• Anti virus software – virus is a malicious code that can infect and spread itself through a user’s email, seocondary storage devices and social network.
  • Protects theuseragainstthese threats
  • Scans everygileandallthememorylookingforevidenceofviruses

Performs many similar tasks serially without the need for user intervention.

• Each jobcanonlydifferinthedataituses
• Have a large number of smiliar tasks
• Can berunwith no user intervention
• Able torunduringout of office hours

Single user – only one user can be active at once

Multi user – run on more powerful computers or servers that can allow timesharing of system resources by multiple people simultaneously.

Multi-tasking – process of swapping applications in and out of the CPU, giving the illusion that they are running in parallel

Multi-programming – stores more than one job in the computer’s main memory at the same time.

Real time-  must respond within a certain amount of time, sometimes considerate to be immediate, to input provided to the system.

An interrupt is an electronic signal oraprocessgenerated signal that is sent to the CPU to inform it hat a device or process requires attention.

Interupt service routine are bits of code that are run when an interrupt occurs

Buffers are used on devices to allow the CPU to perform other tasks while data is being saved

Threading: A methods of splitting a process into multiple smaller processes to take advantage of multiple cores.

Polling:aprocesswillblockuntilanactivityiscompleted.

A setofmechanical and sequential steps that are followed in order to take some form of input and process it to form an output

Flowchartsareusedtorepresentthepseudocode of an algorithm.

Variable – named location in memory that a programmer can use to store data whilst the program is running.

Constants – thevaluewillnotchange.

• One avariable isdefineditalifespan;thiscanbethe whole time the program is running.

Local Variables – can only be accessed by subroutine they have declared in.

Global variables – available throughout to the program to any subroutines.

Self documenting code is code which uses sensible identifiers, good layout and clear code to reduce the need for comments and other forms of documentation

Parameters provide an input into procedures and functions

Procedures do not return values while functions do

Recursion are functions which calls themselves and is a methods of iteration.

Search:

1.Linear – starts at the first index in the array and compare the search item to every item until that item is found

2.Binary – a divide and conquer which requires the initial array to be sorting before.

Sequence is the order in which programming statements are executed Selection will choose one of two paths to follow based on a condition. Repetition oriterationwillrepeat a block of code until a condition is met.