AS Level IT Chapter 2 - Hardware and Software

Hardware

A physical component of a computer system.

device

a hardware component of a computer system

consisting of electronic components.

output device

a device used to communicate data or

information from a computer system.

input device

a device that allows data to be entered to

a computer system.

storage device

a device used to store data on a storage

medium.

storage medium

a medium on which data is stored.

Central processing unit

the CPU carries out the

calculations, executes instructions and processes data.

The CPU consists of an ALU (Arithmetic Logical Unit) and

the CU (Control Unit).

Arithmetic Logical Unit (ALU)

Performs Calculations and

logical operations.

control unit

The CU runs the fetch-execute cycle which

fetches instructions from memory and executes them.

volatile

data is lost when there is no power

non-volatile

data remains when there is no power

motherboard

Printed circuit board (PCB) that connects

the main components of a computer.

RAM (Random access memory)

Memory used to store

currently active programs and volatile data.

RAM uses and what happens when full

used in important multitasking environments.

if full then programs will be closed.

if its full without any active programs or data to move, then secondary storage is used ie, HDD or SSD

is RAM volatile

yes

Read only memory (ROM)

The memory that, once

written to cannot be removed and can only be read.

is ROM volatile?

no, ROM is non-volatile, meaning that if there is no power, the contents of the ROM will be retained

always stores BI/OS

Graphics card

A.k.a Video card/graphics adapter. A PCB

that controls the output to a display screen. it processes and outputs graphics.

sound card

an expandable component that enables the

use of audio components in a computer.

Hard Disk Drive (HDD)

Most common form of

secondary storage for a computer due to its relatively

low cost per MB (megabyte). Data stored on an HDD is

non-volatile. The drive includes a read-write head which sits at the end of an access arm and magnetizes sectors on the disk (platter).

however,

Moving parts increase chance of

failure.

Requires constant supply of electricity when the disk is

spinning.

Speed of access depend on SATA connection used.

...

HDDs be Internally connected to the computer using a

Serial Advanced Technology Attachment (SATA) or

Integrated Drive Electronics (IDE) cable.

Solid State Drive (SSD)

Contains no moving parts and data is stored onto flash memory(non-volatile). Non-

magnetic and largely unsusceptible to damage.

Does not require constant source of power as only

needed when in use.

More than 20% faster access speed than HDD.

however,

More expensive per MB than a hard disk

cloud computing

refers to anything where computer

services are hosted over the internet and not in the

same physical location as the computer being used. Data

stored on banks of servers are accessed remotely.

o Costs are usually a subscription charge that varies

depending on supplier.

o Running costs are included within the subscription

charge

o Speed depends on broadband bandwidth of user and

that offered by supplier.

Monitor

Output device. Connected to the computer using a graphics card port.

a monitor is limited by its resolution

common resolutions are: 1920 by 1080 pixels

3840 pixels × 2160

pen drive

nickname for a thumb sized USB flash drive

that stores data on flash memory and includes an

integrated USB interface. Portability means that they

may get damaged and need replacing.

o Designed for portability so cost per MB varies on size.

o Power only when in use.

o Speed depends on whether the drive uses a USB.20 or

USB 3.0 port. USB 3.0 is faster.

keyboard

consists of a number of buttons, which are

used to input text or to control parts of an interface. Its main limitation is the number of keys available.

mouse

A pointing device, which allows objects to be

selected and manipulated on the screen. The mouse

controls a pointer which is displayed on the screen.

printer

A printer produces a hard copy (printout) from a

computer usually onto paper.

laser printer

Laser printers negatively charges a

cylindrical drum which then attracts electrically charged

toner (powdered ink). The toner is then heated so that it

melts onto the paper.

o Fastest of all printers ranging from 50-200ppm (pages

per minute)

o Typically, twice the cost of a similar featured inkjet

printer

o Toner cartridges are expensive but last longer and

have less cost per page.

o Highest quality of all printers

inkjet printers

Cartridges full of ink in four different colours: black, cyan, magenta, yellow(CMYK) are used to 'squirt' ink onto the paper to form the required printout.

o Speeds of 15-20 ppm in monochrome but colour

speeds are slower.

o Cheapest of all printer types available.

o Inkjet cartridges vary in price but compatible version

can be bought for cheaper than manufacturer versions.

o Good quality but ink can show through thin paper and

smudges can occur.

o Used for: Photographs, charts, small maps, general

office and home printing.

dot matrix printer

printer: A type of impact printer, which uses

a set of pins being driven onto a ribbon, which then

transfers its ink to the paper.

o Very slow compared to other printers.

o Used to be very cheap but now expensive because

they are not mass produced.

o Very low running costs as the ink ribbon lasts a long

time.

o Quality is usually poor.

o Used for: Invoices or receipts requiring duplicate or triplicate paper such as ATMs.

plotter

Used to create vector drawings on large sheets

of paper by moving the paper backwards and forwards and drawing using pens. Today, plotters are mainly Inkjet printers designed to be used with large sheets of paper,

(A2, A1 and A0).

o Time per page to print is slow due to large area.

o Most expensive type of printer.

o Same running costs as an Inkjet printer.

o Same running costs as an inkjet printer. If pens are

used, Quality of line drawings are high.

o Used for: Architectural drawings, large maps, canvas

prints and signs.

CMYK

cyan, magenta, yellow, and key (black).

Light-emitting diode (LED) plotters are used for faster

black and white printouts.

speaker

used to provide sound output from a computer. These can be as simple as a pair of stereo speakers to full surround sound.

camera

used to capture still or moving images

A digital still camera is optimized for capturing still

images but can also capture movies.

• A digital video camera is optimized for capturing movies

but can also capture still images.

webcam

a camera connected to the computer for the purpose of capturing still or moving images while using a computer. Usually not as high quality as dedicated digital

camera or digital video camera.

scanner

A scanner is used to capture two dimensional

(2D) documents in the form of an image. Similar to a

digital camera but are specifically designed to take close-up images of 2D documents.

optical character reader (OCR)

a device that enables

characters on a document to be identified and understood by the computer as letters, numbers, characters and words.

optical mark reader (OMR)

detects the marks that are

made on a multiple-choice document such as a multiple

choice answer paper for an examination.

Magnetic ink character reader (MICR)

magnetic ink is used to print numbers at the bottom of checks and the numbers are printed using the MICR E-13B or CMC-7 font.

barcode reader

used to detect the width of lines and gaps that form a barcode using a laser and a photodiode.

blu-ray disc

an optical storage medium the same shape and size as a compact disc (CD) and digital versatile disc (DVD) and also stores more data than both.

memory card

flash memory on a small card typically used in digital cameras, digital video cameras and phones. Most common formats include Secure Digital (SD) and microSD.

why use storage devices?

so they may access files in the future,

as a backup

Top Tip on input and output devices

input devices allow data to be sent into the computer. Output devices allow the communications of info from a computer. when data is input into a computer, it is processed and then either output from the computer or stored for later use.

software

Programs, which give instructions to the computer.

user interface

communication between the user and the computer system.

system software

Programs that are designed to maintain or operate a computer system are known as system software.

eg antivirus

operating system

the software that operates the computer hardware,

programs that are used to maintain a computer system are known as utility system

operating systems manage hardware by:

allocating memory to software

o sending data and instructions to output devices.

o responding to input devices such as when a key is

pressed.

o opening and closing files on storage devices.

o giving each running task a fair share of processor time

o sending error/status messages to apps or users.

o Dealing with user logons and security.

device drivers

software that comes with external hardware components and sends customized instructions to those specific components.

application software

Programs intended for

productivity or to carry out a task for the user.

word processing

primary function to process words and word processing software features include:

o Tables

o Headers and footers

o Footnotes and endnotes

o Sections

o Formatting text

o Styles

o Spellchecker

o Bullets and automatic numbering

o Automatic contents page

o Tracking changes

o Frames for images

o Text alignment

o Test wrap

o Indentation and tabs

spreadsheet software

mainly used for performing

calculations and modelling like handling financial and

statistical information.

o Contain cells which form the intersection of rows and

columns.

o Work on the basis of -input-process-output whereby formulas allow output to change depending on input.

Database Management Software (DBMS)

used for viewing and editing data within a database. A DBMS features:

o Data entry screens/input forms

o Filters and queries

o Reports

o Graphs

o Security features

o Relationships to link related tables

Graphics manipulation software

designed to manipulate graphics of either bitmap or vector format.

Features include:

o Drawing shapes

o Changing canvas size

o Resizing images

o Adding layers

o Adding text

o Selecting colour based on picking an existing colour

Features of Bitmap graphics manipulation software can

include:

o Filling an area with a colour

o Moving part of the image

o Resizing part of the image

o Erasing parts of an image

Features of Vector graphics manipulation software can

include:

o Filling a shape with colour

o Changing features of the border of a shape such as

thickness and colour

o Combining shapes together into a group

o Moving a shape or groups of shapes

o Resizing a shape or group of shapes

o Aligning objects

Photo editing software

a specific type of graphics

manipulation software focused on editing photographs.

Features include:

o Cropping parts of the photo

o Changing colour balance

o Adjusting the brightness or contrast

o Red eye correction

o Cloning parts of the photo

o Resizing the canvas

o Effects and filters

o Softening (blurring) and sharpening

o Identifying common areas of an image

important fact on videos

recorded videos are known as 'raw' video files (footage)

video editing software

software focused on editing

videos. Features include:

o Importing or capturing raw video

o Clipping the beginning/end or sections of a video

o Adding titles and credits

o Changing speed

o Rotating footage.

o Using more than one video track

o PIP (picture in picture)

o Transitions

o Adding extra sounds

disadvantages of video editing software

uses up a lot of processing time,

requiring large amounts of RAM,

importing raw videos take time,

encoding the final video takes a lot of time.

communication software

cover a range of tasks

including instant messaging, audio conferencing, video

conferencing and email.

audio conferencing uses VOIP (voice over internet protocol)

An Email client usually features:

o Address book of contacts

o Send and receive emails

o Signatures

o Prioritization

o Delaying delivery of emails

o Delivery and read receipts

o Adding attachments

o Calendar integration

o encrypted messages

o multiple account support

o email specific rules

web authoring software

use for creation and editing of websites.

Features include:

o common navigation bar

o preview web pages

o ability publish individual files or sites to a webserver.

o Basic HTML (Hypertext Markup Language) features

o Metadata management

o Forms and form fields and their validation

o Templates

o Interactive features

o WYSIWYG (What You See Is What You Get) or HTML

Code view or both

control software

Control software is used for

controlling devices not part of the computer system.

measuring software

used to measure values from

sensors including but not limited to:

o pressure

o moisture

o temperature

o wind speed

o distance

o pH (acid/alkaline) levels

o lights

o motors

o sound

o heating

apps

another name for a program. A piece of software

that can run on a desktop computer/phone or over the

internet.

applets

a small program that is designed to carry out a

specific task. Cannot be run on its own and must be

executed from within another piece of software. Often

known as add-ons or extensions.

interface

is the boundary between to systems

user interface (UI)

the boundary between the user and the computer system

command line interface (CLI)

allows users to enter text

commands to which the computer system will respond by producing results in text.

o use very little memory

o can carry out complex operations

o can be difficult to learn and use

graphical user interface (GUI)

most common type of

interface and includes Windows, Icons, Menus, Pointers

(abbreviated to WIMP)

o Uses more memory depending on complexity of the GUI

o Intuitive, so easy to learn

o Restrictive for technical users

dialogue interface

using spoken word to communicate

to a computer system.

o hands-free

o ability to recognize and understand spoken word will

vary and can be limited.

o Require users to know what commands are understood by the interface.

gesture based interface

recognizes human motion,

which may include eyeball/lips tracking, identifying hand

signals or whole-body movement.

o Provides more mobility but may be hard to control

o Accuracy problems

designing UI

When designing UI, it is important to ensure that it is

accessible and efficient for the user. Important things to

consider include:

o Colour

o Layout

o Font size

o Quantity of information

o Controls

mental models

a person's understanding of how something works which may differ from person to

person.

utility software

software that performs some sort of maintenance on the computer system and doesn't include the operating system

2 main functions of and antivirus

Anti-virus monitor continually monitors the system for

viruses and malware.

o Check for viruses or malware that may already be on the system, this is known as scanning.

backup utilities

create a second copy of data and programs that are in storage. the backup can be used whenever the user wishes to do so.

data compression

reduces the original size of files so they use up less storage space.

may take time to open the file but the size will be reduced

disc defragmentation

defragments and reorganizes

fragmented gaps of files left after usage on a drive so

that each file is contiguous.

formatting

the process of organizing the tracks on the disc into sectors. When a used disc is formatted, all data is erased.

File copying

allow users to have more control over which files are copied and how they are copied.

deleting

Deleting utilities can overcome restrictions set by an operating system and enable permanent deletion of files.

custom written software

software that is written to meet the requirements of a client.

Expensive because entire development cost is covered

by client

o Takes longer time to develop

o Requirements of the client can be met precisely

o Developers will ensure compatibility with the client's

hardware, software and data

o Bugs are likely since it is not used widely

o Client will have access support from the developer

company

off the shelf software

general purpose software available to a large market.

o Development cost spread between all the customers

who purchase it at a specific price, reducing overall

cost

o Immediately available

User requirements may not be precise/unnecessary

features

o May have compatibility issues

o Large number of users means lesser bugs due to

patches released after identification of bugs

o Wide range of support both from the developing

company and externally

compiler

translates a program written in a high-level

programming language (HLL) into machine code.

o Translates code all at once in advance of execution

o Compiled code will only work on the operating system

it has been compiled for

o Object code ready to be executed without delay

o Compiling takes a lot of time

o Not for on-the-fly testing

interpreter

also translate a program from HLL into machine code.

o Translates code one line at a time

o Source code can be translated into object code for

more than one operating system

o Object code has to be generated, so additional time is

added to the execution time.

o Only the required code needs to be interpreted

o Efficient for on-the-fly testing

misc on ch 2

The file with the machine code is known as the

executable file or the object file.

• The original HLL file is known as the source file.

• Linker: combine different object files within a program

together to form a single executable file.