Elements of Information and Communication Technology (ICT)
Software is a generic term for organized collections of computer data and instructions, often broken into two major categories: system software that provides the basic non-task-specific functions of the computer, and application software which is used by users to accomplish specific tasks.
System software is responsible for controlling, integrating, and managing the individual hardware components of a computer system so that other software and the users of the system see it as a functional unit without having to be concerned with the low-level details such as transferring data from memory to disk, or rendering text onto a display. Generally, system software consists of an operating system and some fundamental utilities such as disk formatters, file managers, display managers, text editors, user authentication (login) and management tools, and networking and device control software.
Application software, on the other hand, is used to accomplish specific tasks other than just running the computer system. Application software may consist of a single program, such as an image viewer; a small collection of programs (often called a software package) that work closely together to accomplish a task, such as a spreadsheet or text processing system; a larger collection (often called a software suite) of related but independent programs and packages that have a common user interface or shared data format, such as Microsoft Office, which consists of closely integrated word processor, spreadsheet, database, etc.; or a software system, such as a database management system, which is a collection of fundamental programs that may provide some service to a variety of other independent applications.
Software is created with programming languages and related utilities, which may come in several of the above forms: single programs like script interpreters, packages containing a compiler, linker, and other tools; and large suites (often called Integrated Development Environments) that include editors, debuggers, and other tools for multiple languages.
Software can be purchased or acquired as shareware (usually intended for sale after a trial period), liteware (shareware with some capabilities disabled), freeware (free software but with copyright restrictions), public domain software (free with no restrictions), and open source (software where the source code is furnished and users agree not to limit the distribution of improvements).
Software is often packaged on CD-ROMs and diskettes. Today, much purchased software, shareware, and freeware is downloaded over the Internet. A new trend is software that is made available for use at another site known as an application service provider.
Some general kinds of application software include:
- Productivity software, which includes word processors, spreadsheets, and tools for use by most computer users
- Presentation software
- Graphics software for graphic designers
- CAD/CAM software
- Specialized scientific applications
- Vertical market or industry-specific software (for example, for banking, insurance, retail, and manufacturing environments)
- Computer Software Packages
- Operating systems – In computing, an operating system (OS) is the system software responsible for the direct control and management of hardware and basic system operations
- Graphics programs – A graphics program is a piece of computer software that enables a user to modify or view graphics files
- Office applications and suites – Office applications suite, also called Offimatic Suite, is a set of computer programs suitable for typical office work
- Utilities and tools
- Collaborative software – Collaborative software, also known as groupware, is software that integrates work on a single project by several concurrent users at separate workstations
- Computer games
Word processors can be used to create any type of text-based document, from a letter to a novel. You can change a document’s appearance using a number of formatting options such as:
- change the font and font size
- bold, italicise and underline words
- colour the text and the background
- highlight words of importance
You can also add tables, images, clip art and shapes to a document. Use formatting sensibly and sparingly.
All word processing applications allow you to:
- enter and edit text
- check your spelling
Mail merge lets you create a template and use it to personalize a document that you’re going to send to lots of people. For example, you write a party invitation that starts ‘Dear James’ and you use James’ name throughout. To turn this invitation into a template, replace all instances of James with a name placeholder. The name placeholder is linked to records in a database that contains all of your guests’ names. Mail merge will use your newly created template to make personalized invitations for all of your guests.
- One standard letter can be written and sent to all customers without having to manually add each name and address.
- The letter can be personalized – it looks as though the letter has been written to the individual person.
- It’s a very fast way to produce hundreds of personalized letters.
- Letters can lack the personal touch.
- The database that provides the information for the mail merge letter must be kept up to date if it is going to be useful.
Desktop publishing software (DTP) is used to create documents like leaflets, brochures and newsletters.
Modern word processors have the basic features of DTP software but features such as templates and frames make DTP software better for complex page layouts.
Templates – examples to base your own document on. Templates provide an easy way of making documents look professional. If you want something that stands out, be aware that the same template can be used by many people.
Frames – boxes that can contain text or graphics. These can be moved around freely and resized to create the layout that you want.
WYSIWYG (What You See Is What You Get)
With WYSIWYG, what is shown on screen is exactly how it will look when printed. A number of office applications work in this way, including DTP software.
Spreadsheets are used for calculations, simple databases and modelling.
A spreadsheet is made up of rows, columns and cells. Columns are labelled alphabetically, starting at A, and rows are labelled numerically starting at 1. Each cell has a unique cell reference. The first cell in a spreadsheet is A1, A2 is below A1, and B1 is to the right of A1. A cell can contain data, labels and formulae.
The formatting options in word processors are present in spreadsheet applications. You can change the font type or font size of the text or make it bold, italicised and underlined in a cell.
Cells can be formatted too. You can change the background colour and add borders to them.
Formulas and functions
Spreadsheets are perfect for performing calculations with data. To do this you need to write a formula. All formulas start with an equals sign (=). You could use a formula to calculate a total. If one of the values that makes up the total changes, the total updates automatically.
More advanced formulas are called functions. These are complex formulas created for you. There are many to choose from and also specialist ones designed for particular jobs or areas of expertise.
Spreadsheet applications can automatically create graphs and charts to give a visual representation of your data.
Presentation software is used to create slideshows. A slideshow is a series of slides. An individual slide can contain text, images, animations, sound and video. Slides can show automatically one after another or the presenter can choose when to show the next slide manually.
A slideshow can act as a visual prompt to a person giving a talk or presentation, or it can give more information about the current topic.
The features of presentation software include:
Slide master – controls the presentation’s appearance and keeps all the slides in the same style.
Animations – special effects to keep your audience interested.
Transitions – different ways to change from one slide to the next, eg the current slide dissolves into the next one.
Speaker notes – the presenter can add notes to remind them what to say when each slide is shown. The notes appear on the presenter’s screen but not on the audience’s.
There are three main types of graphics software:
Some of the basic changes they let you make to an image include:
- contrast and brightness adjustment
- cropping (choosing part of the image and getting rid of the rest)
Most graphics programs create bitmap images and some create vector images too. Bitmap images lose quality when they are resized but vector images do not – they are generally less detailed and realistic than bitmaps though.
Graphics software can read and save to lots of different file types. An image’s file type or file format should be chosen based on its intended use.
- JPG – small file size, used by cameras and for images on the internet.
- GIF – small file size, used on the internet for images that have large blocks of colour.
- PNG – small to medium file size, designed to replace GIF. It is slowly growing in use.
- BMP – large file size, rarely used these days.
- TIFF – very large file size, primarily used in the print industry.
Web browsers can only display images in a limited number of file formats. To make sure your image can be displayed, save it as a JPG, GIF or PNG file.
Some graphics programs have their own file type that only they can open and save in. These are called proprietary file formats.
Photo-editing software, drawing, and painting software share many of the same features and some programs claim to do it all.
Photo-editing software is used to edit photos taken with a digital camera or scanned and saved to your computer.
Airbrushing is a technique that features in photo-editing software. It is used by newspapers and magazines, sometimes to cover up skin imperfections, to change eye colour and to make people look slimmer.
Features of photo-editing software
Not all photo-editing software is equal. Some have more features than others, but here are some of the common features you might find:
- Air brushing can cover up skin imperfections, change eye colour and make people look slimmer.
- Red-eye removal is used to correct the effect a flash can have on eye colour.
- Cropping allows you to select part of the image and get rid of the rest.
- Special effects can make the photo look like an oil painting, sketch or cartoon.
- Brightness and contrast can brighten the photo if it’s too dark or darken it if it’s too light. You can change the contrast or adjust the richness of colours.
- Layers allow you to add elements to an existing photo.
Photo-editing computer programs
There are free, paid-for and open source programs.
- Windows Paint is included with Windows.
- Adobe Photoshop is very expensive and aimed at professionals.
- GIMP is an open source alternative.
- Photo-editing in a web browser
Web browsers are becoming more powerful and can run applications of their own. These applications let you edit your photos within the web browser:
- Photoshop Express Editor
- Sharing and storing photos online
People like to share their photos with family and friends. Some popular services include:
Photos uploaded to online services are often compressed. Compression reduces an image’s quality but also its size, making it much faster to load on to your screen.
Painting software is used to create original pieces of work using your mouse or graphics tablet. A graphics tablet is a touch-sensitive surface that you draw on with a pen. It reproduces what you draw on screen. They are generally preferred by professional designers.
Windows Paint is the most basic painting software and is included with the Windows operating system. Programs with more features are Adobe Photoshop and GIMP, which also allow you to edit photos.
Features commonly seen in painting software are:
- cut, copy and paste – copy and paste parts of one image into another
- pencil or brush tool – choose different thicknesses and edging
- shapes – choose from a selection of shapes, eg squares, circles and triangles
- colour palette – choose from thousands of colours or create your own shade
- fill – fill a shape or area with colour
- zoom – get in close to edit fine details in your image
Painting software outputs bitmap files. Bitmap files lose quality when they are resized.
Drawing software creates and edits vector images. Vector images are made up of lines, curves and shapes based on coordinates. An enlarged vector image will not lose quality.
Examples of drawing software:
- Adobe Illustrator
- Xara Xtreme
There are many different types of animation. They all use frames. Frames are still images that appear as a moving image when they are shown one after another at high speed. Types of animation include:
- Traditional animation – each frame is hand drawn then shown in quick succession.
- Stop motion – many photos are taken. Each photo is a frame and changes slightly. The photos are then shown in quick succession.
- Clay animation – similar to stop motion but uses clay models.
- 2D animation – animating images made in painting or drawing software.
- 3D animation – animating 3D models made in 3D software.
There are many programs available to produce the above types of animation, for example:
- MonkeyJam – stop motion and clay animation
- Claymation Studio – stop motion and clay animation
- I Can Animate – stop motion and clay animation
- Adobe Fireworks – 2D animation
- Ulead GIF Animator – 2D animation
- Toon Boom Studio – 2D animation
All of these programs work with bitmap images, with the exception of Fireworks, which works with vector images, too. Features differ from program to program but some of these programs let you:
- create new images with inbuilt tools or import an existing image
- add existing sounds or choose from the program’s library
- increase the smoothness of animations by using a higher frame rate
- create layers to separate the different bits of an animation
- use a timeline to keep track of your animation
This is arguably the most advanced vector-based 2D animation program. Adobe Flash is commonly used to create games, adverts and interactive applications.
3D modelling and animation
Programs that can create animated 3D design plans or Computer Aided Design (CAD) are:
- 3DS Max
- Xara 3D
- Google Sketchup
3D modelling and animation programs allow:
- images to be viewed from any angle
- greater accuracy as 3D models are based on real objects
- 2D and 3D modelling and animation
- access to a library of existing 3D models
Other programs that create 3D models and animate them are:
- Illusion Mage
They are ideal for creating:
- high-quality 3D graphics
- cartoon-animated films
- animated 3D models
- 3D scenes with sky, water, grass, and trees
- special effects
Database software stores information in an organised way. Individual bits of data are stored in fields. Each field has a unique name, eg Address.
A record is a collection of fields that all relate to one another, together they are information. A record about a car would include its:
- registration or number plate
A table is a collection of records. In the example given, a table would contain individual records of cars.
Key fields exist as a unique identifier. In a car salesman’s database ‘Registration’ would be a suitable key field. None of his cars have the same number plate, but some of them will be made by the same manufacturer or share the same colour. The key field allows the computer to separate each car’s record. Key fields are sometimes referred to as primary keys.
Operating System Functions(photo credit to the owner)
In any computer, the operating system:
- Controls the backing store and peripherals such as scanners and printers.
- Deals with the transfer of programs in and out of memory.
- Organises the use of memory between programs.
- Organises processing time between programs and users.
- Maintains security and access rights of users.
- Deals with errors and user instructions.
- Allows the user to save files to a backing store.
- Provides the interface between the user and the computer – for example, Windows Vista and Apple OSX. For more information, see the User Interfaces study guide.
- Issues simple error messages.
In a larger computer such as a mainframe the operating system works on the same principles.
Modes of Operation
Computers can operate in many different ways requiring different and complex operating systems.
Demonstration of different types of processing. Eg Multi, real-time, interactive, batch, multi-tasking, multi-access processing
When the computer has to react within a guaranteed time to an input, a real-time operating system (RTOS) is used. For example, the engine management system within a car uses a real-time operating system in order to react to feedback from sensors placed throughout the engine.
A real-time operating system does not necessarily have to be fast. It simply has to be quick enough to respond to inputs in a predictable way. Embedded computers often contain an RTOS as many are used to control something.
Computers operating in real time are often dedicated to the control of systems such as industrial processes, planes and space flights.
Multi-programming is a method of operating such that several programs appear to be running at once.
The operating system switches jobs in and out of processor time according to priority. For example, while one job is being allocated printer time, another will be being processed in memory. The processor is so fast that it seems that many jobs are being processed at the same time.
A batch processing system is where programs or data are collected together in a batch and processed in one go. Typically the processing of payrolls, electricity bills, invoices and daily transactions are dealt with this way.
This method of operation lends itself to jobs with similar inputs, processing and outputs where no human intervention is needed. Jobs are stored in a queue until the computer is ready to deal with them. Often batch processed jobs are done overnight.
An interactive processing system is where the tasks on the computer system require a continual exchange of information between the user and the computer system. It can be seen as the opposite of batch processing.
This isn’t just about running more than one application at the same time. Multi-tasking allows multiple tasks to run concurrently, taking turns using the resources of the computer.
This can mean running a couple of applications, sending a document to the printer and downloading a web page.
Multi-access or multi-user
Modern personal computers can allow multi-user access. A multi-access (or multi-user) system is one where several users can use the same system together via a LAN.
The CPU deals with users in turn; clearly the more users, the slower the response time. Generally, however, the processor is so fast that the response time at the most is a fraction of a second and the user feels they are being dealt with immediately.
Hardware is a comprehensive term for all of the physical parts of a computer, as distinguished from the data it contains or operates on, and the software that provides instructions for the hardware to accomplish tasks.
The boundary between hardware and software is slightly blurry – firmware is software that is “built-in” to the hardware, but such firmware is usually the province of computer programmers and computer engineers in any case and not an issue that computer users need to concern themselves with.
A typical computer (Personal Computer, PC) contains in a desktop or tower case the following parts:
- Motherboard which holds the CPU, main memory and other parts, and has slots for expansion cards
- power supply – a case that holds a transformer, voltage control and fan
- storage controllers, of IDE, SCSI or other type, that control hard disk , floppy disk, CD-ROM and other drives; the controllers sit directly on the motherboard (on-board) or on expansion cards
- graphics controller that produces the output for the monitor
- the hard disk, floppy disk and other drives for mass storage
- interface controllers (parallel, serial, USB, Firewire) to connect the computer to external peripheral devices such as printers or scanners
Computer Hardware Categories
So what are the main components of a computer system?
- Motherboard – A motherboard is the central or primary circuit board making up a computer system or other complex electronic system
- Storage – The terms storage or memory refer to those parts of a computer that retain data for some period of time, possibly even after the computer is turned off
- Input/output devices – or I/O, refers to the interfaces that different functional units of a system use to communicate among each other, or to the signals sent through those interfaces
Input devices, Processing and Output Devices
Manual Input Devices
The most common manual input devices are the keyboard and mouse. Other manual input devices include:
Each button on a concept keyboard relates to a particular item or function. Buttons can be labelled with text or a picture. Fast food restaurants often use concept keyboards because very little training is needed to operate them and they’re efficient – a single button can order an entire meal.
Used as an alternative to a mouse. To operate it the user rotates the ball which moves the pointer on screen. They are particularly easy to use for those with limited movement in their hands and are often used in Computer Aided Design (CAD) for their increased precision over a mouse.
Joysticks used to be popular with gamers but have slowly been replaced by other types of game controller. In construction, joysticks are used to control machinery such as cranes.
A digital camera takes pictures and can usually record video too. The pictures it takes and the videos it records are stored in files. These files can be copied to a computer and later edited.
Microphones are used to input sound. In computing they can be used with voice recognition software and a word processing application to enter text. Webcams commonly have microphones built-in too.
A touch-sensitive visual display unit (VDU) or screen has a grid of light beams or fine wires criss-crossing the screen that are used to detect touch. Many mobile phones use touch screens and do away with the keypad entirely. They’re often used on cash machines and in shopping centers too. Touch screens are robust, easy to operate and easy to reprogram.
A video digitizer takes an image from a video camera or television and digitizes it so it can be read by, and stored on, a computer. Video sequences captured using a video digitizer are often used in multimedia presentations.
A scanner can be used to digitize images. They’re similar to a photocopier but they make a digital copy instead of a physical copy. They can also be used with optical character recognition (OCR) software to scan in text that is then editable.
Automatic Input Devices
Sensors are often used as part of a feedback cycle. They collect data continuously and are typically linked to a control program that specifies acceptable levels, eg the minimum and maximum temperature in a greenhouse. The control program decides what to do next based on the data it’s fed by the sensors.
Barcodes are represented by black vertical bars and are read by a barcode reader. Barcodes are printed on nearly every product you buy, each product has a unique code. When read, information stored in the shop’s database is recalled, such as the product name and price. This information later appears on your receipt. The scanning process also assists in stock management, reducing the stock by one each time a product is scanned/sold.
Magnetic strip (or stripe) reader
Magnetic stripes are built into many plastic cards such as debit or credit cards and personal identity cards. The magnetic strip on the back of the card can hold the personal details of the card owner and, with the necessary PIN, will allow access to secure information, eg bank account details. Data stored on the strip is scanned and input into a computer system by a magnetic stripe reader.
Magnetic Ink Character Reader (MICR)
Magnetic ink characters appear at the bottom of cheques. Banks use MICR to read the numbers from the bottom of cheques to obtain data such as account numbers and bank sort codes. A particular font is used that makes it easy for the machine to discriminate between characters. The ink is magnetised, this makes it immune to creases and dirty marks.
Optical Mark Reader (OMR)
An OMR reads marks made by pencil on a printed form into the computer. OMR systems are suited to reading pre-printed forms and check boxes such as lottery number selection sheets and multiple choice exam papers.
Central Processing Unit
The CPU (Central Processing Unit) is the part of a computer system that is commonly referred to as the “brains” of a computer. The CPU is also known as the processor or microprocessor.
The CPU is responsible for executing a sequence of stored instructions called a program. This program will take inputs from an input device, process the input in some way and output the results to an output device.
CPU’s aren’t only found in desktop or laptop computers, many electronic devices now rely on them for their operation. Mobile phones, DVD players and washing machines are examples of equipment that have a CPU.
Common output formats are printed paper, sound, video and on-screen documents. They let the computer communicate with the user. Examples of devices that take advantage of these formats are:
The most common output device is the monitor or VDU.
Modern monitors, where the case isn’t more than a few centimeters deep, are usually Liquid Crystal Displays (LCD) or Thin Film Transistors (TFT) monitors.
Older monitors, where the case is likely to be around 30 cm deep, are Cathode Ray Tube (CRT) monitors.
- Laser printers are quite expensive to buy and run but produce a high quality output and are quiet and fast.
- Ink-jet printers offer black and white or colour printing with reduced levels of quality and speed. Colour ink jet printers are cheaper to buy than colour laser printers.
- Dot matrix printers are not so common today. They are comparatively noisy and low quality but are cheap to run and are used when carbon copies or duplicates need to be made, such as for wage slips. Also, they are useful in dirty environments such as a garage because they are much sturdier than the other two types of printer.
A plotter can be used to produce high quality, accurate, A3 size or bigger drawings. They are usually used for Computer Aided Design (CAD) and Computer Aided Manufacture (CAM) applications, such as printing out plans for houses or car parts.
Other output devices
Many other types of output device exist including:
- switched outputs
- mechanical devices, eg a robot arm
Main store (or computer memory) is divided into Read Only Memory (ROM) and Random Access Memory (RAM).
ROM is memory that cannot be changed by a program or user. ROM retains its memory even after the computer is turned off. For example, ROM stores the instructions for the computer to start up when it is turned on again.
RAM is a fast temporary type of memory in which programs, applications and data are stored. Here are some examples of what’s stored in RAM:
- the operating system
- the graphical user interface (GUI)
If a computer loses power, all data stored in its RAM is lost.
Storage capacity and file size
Storage capacities and file sizes are measured (from lowest to highest) in:
An operating system abbreviates these measurements, eg 1 megabyte becomes 1MB (megabyte).
The Hard Disk(photo credit to the owner)
The main internal backing store is a computer’s hard disk.
A hard disk stores:
- the operating system
- software applications or programs
- the majority of your data files
Hard disks spin at very high speeds (around 7,200 RPM – revolutions per minute) within a sealed unit inside the computer. Hard disks store large amounts of data – 200 GB to 1TB is common in desktop computers. The data stored on a hard disk is retained until deleted, but it needs to be loaded into main store RAM before it can be used.
Floppy and zip disks
Floppy disks became popular in the 1970s. The most common format was 1.44 MB, capable of holding only very small amounts of data. Computers need a floppy drive to read floppy disks, and many modern computers are no longer supplied with a floppy disk drive because we now work with much larger files.
Now we are capable of storing at least 16 GB of data on a memory card which is, physically, six times smaller than a floppy disk. It would take roughly 11,111 floppy disks to store 16 GB of data.
A small 16gb micro SD cards compared to its equivalent of 11,000 floppy disks
In the past, floppy disks were used to:
- transfer small files of data from one machine to another
- backup important small files that are stored on your hard disk
- store restricted files that you don’t want other users of your computer seeing
Zip disks are like large floppy disks but can store 250MB or more of data. To read them a computer needs a zip drive. Their use is similar to that of floppy disks.
External Backing Stores – Optical Discs(photo credit to the owner)
There are several different types of optical disc, although they all look pretty much the same.
CD (Compact Disc)
Optical discs that use the same technology as music CDs. They store up to 700MB of data. CDs can be used for multimedia applications such as encyclopedias and can store pictures, sounds and video clips or anything else that will fit.
There are several formats on the market, such as:
- CD-ROM – read only, the data is written to them before they are sold.
- CD-R – meaning CD-Recordable, the user can write data to the CD once or fill it over time using multi-session (writing to the same disc on separate occasions).
- CD-RW – meaning CD-ReWritable, the CD can be written and re-written to. Unlike multi-session discs, existing data can be overwritten.
DVD (Digital Versatile Disc)
DVDs are the same physical size as CDs but hold much more data – a single sided disc can hold up to 4.7 GB. DVDs are commonly used for storing video so you will often see them measured in minutes, eg 4.7 GB = 120 minutes.
There are several formats on the market, such as:
- DVD-ROMs – read only, the data is written to them before they are sold.
- DVD-R – meaning DVD-Recordable, the user can write data to the DVD once or fill it over time using multi-session.
- DVD-RW – meaning DVD-ReWritable, the DVD can be written and re-written to. Unlike multi-session discs, existing data can be overwritten.
To read from and write data to CDs and DVDs you will need a suitable drive. CD/DVD drives are able to:
- read all CD and DVD formats
- write to CD-R, CD-RW, DVD-R and DVD-RW
Data is written to and read from the discs using a laser.
Principally used for backup of important files from the hard disk and for the long term storage and archiving of data.
- they are small, robust, portable and provide low cost storage per GB
- they are very slow to write to and read from
- serial access means all the data on the tape must be read before you can access the data you need
External hard disks
An external hard disk can store very large amounts of data, eg 1TB, and can be plugged into your computer via a USB or FireWire port to provide extra storage. They’re essentially the same as the hard disk in your computer but due to the casing are usable externally.
- high capacity, eg 1TB or more so they can be used to backup data or move large amounts of data between machines
- they are often quite large and therefore inconvenient to carry around
- they have moving parts so are more likely to break, especially if dropped
A memory stick is a ‘pen top’ sized USB device and can be used in a similar way to a floppy disk but it is inserted into the USB port – it is then seen by the computer as a removable drive. They typically come in sizes from 512MB to 32 GB upwards depending on the price paid.
- memory sticks can hold large quantities of data
- they are extremely portable, so the user can take them wherever they go
- they are durable, because they have no moving parts
- portable storage devices in general are more likely to be lost, stolen or damaged
A memory card is a stamp-sized USB device and can be used in a similar way to a floppy disk but it is inserted into either a memory card reader or a USB converter – it is then seen by the computer as a removable drive. They typically come in sizes from 1 GB to 32 GB upwards, depending on the price paid. There are many available memory card formats, but since 2010 the SD card became the more favoured format.
- memory cards can hold large quantities of data
- they are extremely portable so the user can take them wherever they go
- digital accessories such as compact cameras and mobile phones are able to read and write to memory cards allowing the user to transport large collections of photographs, songs or information with them
- they are durable because they have no moving parts
- Memory cards, specifically the micro SD card, are the smallest storage devices available. This means they are more likely to be lost, stolen or damaged.
- All computers do not come with memory card readers built in. Users will often be required to purchase a card reader or USB converter to view the data on a card.
Backing up and Archiving data
Data needs to be backed up for many reasons:
- a user may delete an important file
- hard disks can fail
- a virus can wipe out data
- a fire may destroy the building where the data was being stored (businesses will often store their backups off-site)
If the data wasn’t backed up then the consequences could be disastrous depending on what data was lost. If a business lost details of all the payments it had yet to receive the business could go bankrupt as they wouldn’t know what was owed to them or by who.
Advances in technology have allowed the development of magnetic tape and so businesses typically still use it to backup important data. Your average home user may not backup their data but those who do will most likely use an external hard disk.
Frequency of backups
Some data is more valuable than other data and some data is changed more frequently than other data. These are the kind of issues that must be taken into account when deciding how often to backup data.
The value of the data should determine how frequently it is backed up.
If the data doesn’t change often then it doesn’t need to be backed up as often, maybe just after each change. If the data changes frequently then it should be backed up frequently (maybe every evening).
Some data may not be being used very often but it may still be useful or needed in the future. In this case data can be archived. Archived data is copied to a suitable storage medium (perhaps DVDs or magnetic tape) then it is stored safely and securely. The original data is then deleted from the computer system. This is done to free up storage space for new data.
Sources: BBC.co.uk; https://www.techopedia.com/definition/24152/information-and-communications-technology-ict; http://www.openprojects.org/index.htm