digital technology

txt

plain text document. can be opened in any word processing program to allow text editing

wav

Windows Audio Waveform. uncompressed audio file format. a file format that stores audio.

midi

musical instrument digital interface. captured via a serial interface connected to a electronic musical instrument.

jpeg

joint photographic expert group, supports compression, image file, often used on web pages, lossy, bitmap

png

portable network graphics, image file, lossless, bitmap.

gif

graphics interchange format. supports bitmapped image files. lossless. file sizes are small. they can be animated

rtf

rich text format. supports formatting. text file. ocr scanners usually save scanned documents in rtf format.

csv

comma seperated value. used by databases and spreadsheets. columns are seperated by commas. text file.

wma

windows media audio. developed by microsoft for windows media player.

mp3

audio file. lossy

adc

analogue to digital converter.

hertz (hz)

the frequency at which samples are taken is known as the sample rate, which is measured in Hertz (hz)

mpeg

moving/motion picture experts group. lossy. a group of experts who developed standards for compressing digital video. video file.

avi

audio video interleaved. multimedia file format, can contain both audio and video content allowing synchronous audio-with-video playback. lossless.

mp4

sound and video file. lossy. can store still images and text subtitles. can be used for streaming across the web.

sample rate

number of audio sound samples captured per second to represent the sounds digitally.

bit rate

the quality of the data measured in bits that is processed in a given amount of time

bit depth

the number of bits used for each sound sample

analogue signal

a continous varying signal that represents a physical quantity

sample

the reuse of a portion of a sound recording in another recording

pdf

portable document format. developed by adobe systems. can be created from a range of files (microsoft word document or powerpoint presentation)

pict

standard file format for apple graphics. support both bitmap and vector graphics. image file.

tiff file

tagged image file format. store bitmapped images. portable. lossless. file sizes can be larger.

text formatting

when text is displayed in a special, specified style

buffer

an allocated part of memory that is used to store a downloaded part of the video before it is watched. a buffer is used to download the next part of a video to prevent disruptions in streaming.

system software

system software is the interface between computer hardware and its user application software

operating system

essential piece of software that manages all the programs being used on the computer

user interface

(ui) the apps and command buttons that the user sees when the system loads

utility programs

programs that allow the system to carry out specific tasks to assist the os (example: updates)

advantages of general purpose software

cheap. easily available to download. won't have serious bugs or problems because it would have been tested a lot. lots of user support.

advantages of tailor made/bespoke software

the company will get the exact software/system they need. the software will work exactly how they want it to and only have the features they need to use.

disadvantages of tailor made/bespoke software

takes a long time to develop. costs a lot of money. the company may need to employ programme testers. little user support and online help.

memory management

the os keeps track of every memory location. it is responsible for making memory available for different processes (example: allocating free space in memory to programs)

virtual memory

a section of the storage device which is temporarily used as RAM

ram

Random Access Memory

file management

the os is responsible for organising files in a computer system. it organises where and how files are stored, found, read and deleted.

file management

the file management system is what allows you to see data held on secondary storage devices such as a usb drive/flash drive

file management

provides a graphical user interface (gui) for accessing file systems

gui

user interface/graphical user interface. used to interact with the computer through icons and menus

processing time

the os makes it possible to run multiple programs at once

processing time

several programs can be stored in ram at the same time while being ran, but only one program is processed by the cpu at any one time.

cpu

central processing unit

cpu

the os controls which process is being executed by the cpu at any time. the os manages access to the cpu between programs. this allows a computer with a single processor to multitask

scheduling

the job of working out when to swap processes. this swapping happens so fast, it appears all processes are running at the same time.

cpu

too many processes can cause the cpu to work especially hard which can seem as though programs have stopped working or are running very slowly

user interface

provides the option to open applications, run them, shut them down etc

managing hardware

the os can communicate with peripherals with its device drivers

multi programming example

connecting a peripheral

real time processing examples

blood pressure machines. scanners. car mechanics diagnosing problems. diagnostics

interactive processing examples

spreadsheet software. database software.

antivirus

prevents computer viruses. can detect, block and quarantine computer viruses. needs to be updated reguraly because new viruses are created all the time

computer virus

malicious piece of software designed to copy itself over and over again and attach itself to other programs. steals and attacks data on the computer

task scheduling

most operating systems provide task scheduling facilities which can allow you to launch programs at pre-defined times. (example: teacher scheduling work on gc)

incremental backup

only backing up data which has changed since the previous backup

full backup

when everything on a hard disk is backed up. can take a long time.

batch processing

when data is collected together and processed in one go. usually done overnight.

real time processing

an os that can react fast enough to events in the outside world to control an output.

peripherals

any device that connects to a computer. i/o devices

i/o

input/output

file management example

file explorer

tailor made or bespoke software

a company has a software specifically designed to meet their needs

general purpose software

the sort of software you use for home/school use. usually downloaded of a website/application store. large storage size because it has a lot of features that not all users will use.

application software

can gain access to hardware. carries out tasks that the user in interested in doing.

drivers

software that allows the os to communicate with hardware

hardware examples

cpu. discs. mouse. printer

dpi

dots per inch

defragmentation

hard drive saves files as 'fragments' on a disk. defragmentation moves file fragments so they are next to each other on the disk. this reduces time needed to read files.

backup and restore

the os can schedual backups at specific time scheduals and at regular intervals.

utitlity programs

helps users configure, analyse and optimise and maintain a computer. they often come part (built in) with the os. (example: disk defragmentation, task scheduling)

time sharing (multi user processing)

the cpu allocates a period of time to each user in multiuser processing. the process is so fast that the user feels they are being dealt with immediantly.

multi user programming

allows several users to have access to computing resources at the same time. the cpu will deal with each user.

multi access or multi user examples

telephone call centres. collaboration.

multi tasking examples

more than one task being done at a time. screen recording.

batch processing examples:

billing such as telephone bills

resolution

higher resolution images need more storage space.

image resolution

the quality of an image is determined by its resolution.

image resolution (1280 x 720)

represented by two numbers. the first number is the number of pixels displayed horizontally (1280). the second number of pixels are displayed vertically (720).

image resolution

the more pixels used in a image, the higher the resolution and the sharper the image

vector graphics

they do not depend on resolution for quality. they can be saved as smaller files. can be easily edited without loss of quality.

vector graphics

based on mathematical objects such as lines, curves, and shapes. you can edit these objects seperately, by changing the colour, size or position of the object.

bitmap graphics

zooming in or enlarging pixels can cause pixelation. the pixels will become larger on screen and look like blocks of colour. the quality of a bitmap image will be poor when it is enlarged too much.

bitmap images

bitmaps images can be compressed to reduce the file size but this may result in a loss of quality.

data compression

used to reduces file sizes and at the same time, maintain the quality of the data contained in the file

data compression

websites require fast image and audio download speeds. reducing storage requirements of image files and audio files means faster upload and download speeds to an from the internet

data portability

the ability to transfer data from one computer to another or from one software application to another without having to re-enter the data

types of compression

lossy and lossless

lossy compression

reduces file sizes by removing some of the data

lossless compression

maintains the quality of the file, therefore data is not lost

megabyte

1024 kilobytes. abbreviated to mb

kilobyte

1024 bytes. abbreviated to kb. equivalent to 1024 characters on screen.

byte

8 bits are known as a byte. each character is represented by 8 bits. (example: when you type 'A', the computer processes this as 01000010)

nibble

the name given to a group of 4 bits

bit

the smallest unit of storage. short of binary digit. either a 1 or 0

gigabyte

1024 megabytes. abbreviated to gb

terabyte

1024 gigabytes. abbreviated to tb

adc

an analogue to digital converter will sample a signal at regular intervals. samples are then converted to digital format

bitmap graphics

the higher the resolution of the image, the more storage space it will use.

bitmap graphics

the higher the quality of the image, the more pixels it will contain, the better the resolution

bitmap graphics

made up of a grid of pixels. phone pictures and scanned images are examples.

pixels on a computer screen

the number of pixel on a computer screen depends on the size of the screen and the graphics card