What you need to know

Click on the following for definitions of the key terms you need to know:
| data | information | input devices | OCR | OMR | output devices | | peripheral | baud | bar code | compatibility | MHz | dpi | storage | Flash Memory | bit | KB | MB | GB | TB | verification | validation | ROM | RAM | ASCII & unicode | encryption | firewall | virus | Trojan horse | worm | logic bomb | Platform Click on the following links for additional information:

See also: authentication and cards


A computer is a device that takes data, processes the data and the outputs data. INPUT => PROCESS => OUTPUT. Data comes in many forms such as letters, numbers and symbols. The following are examples of data:
  • 9112001
  • 677433
  • 210021, 23, 54, 43, 65, 32, 21, 12
  • ab


What is the difference between data and information?

Data has little meaning until it is turned into information. Data consists of numbers, words, sounds and images which have no meaning attached to them. For example 10082006. Once you are shown these same numbers in the format of 10/08/2006, you realise that they are a date, at which point they change from being data and become Information.

This could be a date
Predicted grades for 6 IB Diploma subjects
210021, 23, 54, 43, 65, 32, 21, 12
Student ID followed by the 7 classes
Extended Essay and TOK predicted grades

Information is data that has been processed in such a way as to be meaningful to the person who receives it. INFORMATION = DATA + CONTEXT + MEANING.
Taking the example: 6774332
DATA: 6774332
CONTEXT: It is a list of the 6 grades (3 HL and 3 SL) plus bonus points achieved by a student doing the IB Diploma
MEANING: The student has an overall score of 32 out 45 and will therefore be awarded an IB Diploma.

For extensive details of data, please go to the data section at the Teach-ICTwebsite.

input devices

Manual Input Devices are the most common input devices are the keyboard and the mouse/touchpad. You should be familiar with the keyboard, mouse/touchpad, scanner, concept tablet and the touch screen.

Automated Input Devices are devices will input data automatically once the data is presented in a suitable format. Examples are OCR, OMR, magnetic stripe readers and magnetic ink readers.

Assisted Input Devices are devices have been developed in order to provide computer inputs in non-standard ways.
Find out about these input devices at Teach-ICT


Optical Character Reader or Optical Character Recognition.

An Optical Character Reader is a combination of scanner and software that converts printed text into electronic ASCII characters. For example converting paper records into electronic files or scanning invoices into spreadsheets. However conversion is often not perfect and so someone has to read the results and correct them and it can be a slow process if you are converting a large number of paper records.

For online optical character recognition, go to this website

Here is an image of an ITGS multiple choice question (please note that paper 1 used to be in multiple choice format).
Before scanning and converting to OCR

Using OCR, the following text was given - note that there are a few errors - however these would be quicker to correct than typing in the entire question.

What flle format is used to store manuals on a CD-ROM so that they retain the same appemnce
as the original printed version?
B- Jpeg (ips)
c. pdf
D. sylk


This device is designed to be able t o read markings that have been placed in specific places on a form or card. The person filling out the form/card will either colour in a series of small squares or perhaps make a cross within the square. The device then scans the card and senses where marks have been placed.

output devices

An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system to the outside world, such as from a computer to outside world).

Speaker, Printer, Monitor, Fax


A peripheral is an external device connected via cables to the system central processing unit, but not part of it; it expands the host’s capabilities.
Keyboard, Monitor, Image scanner, Microphone, Webcam


bar code

A barcode is an optical machine-readable representation of data, which shows data about the object to which it attaches.
It can be read with a scanner (Barcode Reader), which is a reading tool that uses light to read universal product codes, inventory codes, and other codes created out of patterns of variable-width bars.
For example, Barcode can be found on every snack we often eat, and is read with a barcode reader on a counter.


Compatibility is the ability of a software program to run on a specific computer system. Also, the ability of a hardware device to function with a particular type of computer.
Not all software and hardware can be run on a particular CPU architecture. For example, most of “compiled software” applications are compiled for different CPU architectures and operating system to allow it to be compatible with the different system. But “interpreted software” can run on many different CPU architectures and operating systems.
And also for instance, many of hardware for Mac OS X are proprietary hardware with drivers unavailable for use in operating systems such as Linux and Windows.


A 'Hertz' is another word for 'cycles per second'. It is a measure of frequency and computer clock speed. 'Mega' is the metric term for one million. So 1MHz is 1 million cycles per second.For example a computer running at 1MHz means that its internal clock is 'ticking' a million times per second.


Dots per inch (DPI) is a measure of printing resolution, in particular the number of individual dots of ink a printer or toner can produce within a linear one-inch (2.54 cm) space.
From: www.techwarelabs.com


This includes but is not limited to:
  • CDs
  • DVDs
  • Flash Memory
  • Hard Drives
  • RAM and ROM
  • Magnetic tape (used for backup)

Go to this Teach_ICT GCSE website for general information on storage.

Flash Memory

The following is from:
Tyson, Jeff. "How Flash Memory Works." 30 August 2000. HowStuffWorks.com. <http://www.howstuffworks.com/flash-memory.htm> 09 January 2010.

We store and transfer all kinds o­f files on our computers -- digital photographs, music files, wor­d processing documents, PDFs and countless other forms of media. But sometimes your computer's hard drive isn't exactly wher­e you want your information. Whether you want to make backup copies of files that live off of your systems or if you worry about your security, portable storage devices that use a type of electronic memory called flash memory may be the right solution.
Electronic memory comes in a variety of forms to serve a variety of purposes. Flash memory is used for easy and fast information storage in computers, digital cameras and home video game consoles. It is used more like a hard drive than as RAM. In fact, flash memory is known as a solid state storage device, meaning there are no moving parts -- everything is electronic instead of mechanical.
Here are a few examples of flash memory:
  • Your computer's BIOS chip
  • CompactFlash (most often found in digital cameras)
  • SmartMedia (most often found in digital cameras)
  • Memory Stick (most often found in digital cameras)
  • PCMCIA Type I and Type II memory cards (used as solid-state disks in laptops)
  • Memory cards for video game consoles
Flash memory is a type of EEPROM chip, which stands for Electronically Erasable Programmable Read Only Memory. It has a grid of columns and rows with a cell that has two transistors at each intersection.

Flash memory is becoming cheaper and more widely used. Consider the advantages of having flash memory in your iPod instead of a hard drive.


A bit that is the smallest amount of information that a computer can store. It can be set to 0 (false) or 1 (true), this is called binary. Eight bits make a byte.


A kilobyte is a measure of computer memory or storage. It is generally thought of as 1,000 bytes. However, to be completely correct, it is actually 1,024 bytes.



A megabyte is generally thought of as one million bytes or 1,000 kilobytes. However, to be completely correct, it is actually 1,048,576 bytes or 1,024 kilobytes.


A gigabyte is 1024 MB (although you will commonly see it referred to as 1,000 MB)


A terabyte is 1,024 GB. Terabyte hard disks are now quite common for backup and storage.


Verification means to check the data that you have entered against the original source data. When data is transcribed from one medium to another there is always a danger that errors will be introduced. The copy will not then be the same as the original. This is particularly true if the transcription is being done manually as when a human operator reads a source document and uses a keyboard to transcribe the data to a computer readable format. Verification is used to check that data is entered correctly and that there are no transcription errors. If data has been copied automatically from one format to another then the computer will automatically compare the two versions and inform the user if are any differences. However if the data has been entered manually, the data must be checked manually against the source document and the error corrected. An example of this is when setting a new password - you are usually asked to key the password in a second time to ensure that you didn't make a keying error the first time. The main aim of verification is to trap transcription errors – errors in transferring the source
data into the computer. However it cannot guarantee accuracy:
  • if the original data was incorrect the data will be entered wronglyi
  • if the data was entered twice, it may have been entered twice incorrectly
  • if the data was being manually checked, mistakes can creep in.

Verification for passwords


Validation is performed by the computer at the point when you enter data. It checks the data against the set of validation rules which you set up when developing your new database or spreadsheet system. Validation aims to make sure that data is sensible, reasonable and allowable. For example, only allow a value between 0 and 100.

See mini web-sites in www.teach-ICT: A' level version, GCSE version


Read Only Memory (ROM) is the memory that stores the instructions that the computer uses when it is first turned on (boots up). This is also known as the BIOS (Basic Input Output System). It allows the computer to check details such as the type of hard disk installed, the amount of RAM installed, the type of CPU being used. Because the data is 'read only', it can be read but not changed by the user. The key thing to remember about ROM is that the data is not erased when the computer is switched off - the data is stored permanently, so it is called 'non-volatile memory'.


Random Access Memory is the memory that the computer uses volatile. This means that the computer only retains the data stored in RAM as long as there is a power supply connected. Data is typically stored in RAM temporarily for use by the process or while the computer is operating. FPM, EDO, SDRAM, DDR, etc. are all types of RAM. RAM is like your short term memory - it holds all the information, portions of the software programs and data that you are working on. The more programs that you have open on your computer, the slower your computer becomes because it has to swap sections in and out of the RAM.

ASCII & unicode

ASCII stands for American Standard Code for Information Interchange. There are 128 standard ASCII codes, each of which can be represented by a 7 digit binary number from 000000 through to 11111. The letter 'A' is represented by the code: 01000001. The letter 'B' is represented by the code: 01000010. ASCII is limited to 128 variations. This allows for the full use of the Roman alphabet (A through to Z and a through to z) plus the numbers 0-9, a range of punctuation and special characters. However this is limiting for non-Roman languages such as Japanese, Arabic, Chinese. Unicode is a 16-bit character encoding scheme allowing characters from Western European, Eastern European, Cyrillic, Greek, Arabic, Hebrew, Chinese, Japanese, Korean, Thai, Urdu, Hindi and all other major world languages, living and dead, to be encoded in a single character set.


Encryption means to scramble a message in such a way that only the people who are meant to read it can do so. A message sent 'in the clear' looks like: "This is a message anyone can read" and the encrypted message looks like gibberish: *773 *(*+_08*@(*()(*&^*

Encryption works by both people making use of a secret 'key' that only they know (or at least their computers know). The original message is mixed in with the key to create a secret message. This is done by some very crafty mathematics so that it is very very hard for someone to crack the code - very powerful computers working for a long time would be needed to crack a good code.


A firewall is a program or hardware device that filters the information coming through the Internet connection into your personal computer or into a company's network.
It is set up to allow mainly one way access, i.e. you can go out onto the Internet and access pages, but it checks everything coming back against a set of rules. If the data coming back is from an unauthorised source, then it is blocked.


A computer virus is a piece of program code that, like a biological virus, makes copies of itself by attaching itself to another program. The virus can waste the host's resources, and sometimes destroy or change files. While viruses are usually malicious - destroying data or crashing network services - many do nothing or are just annoying (for example, displaying a message to the user). Many viruses are made to wait a long time before doing anything, usually destroying data on a certain day, like a holiday. Viruses are usually spread by a computer network, by e-mail, or by removable media, like a floppy disk or memory stick.

Trojan horse

A type of 'malware' software. A trojan seems to do an useful task and so the user will use it. But in the background, the trojan is also carrying out its real purpose which is hidden and unknown to the user. For example, you download a free game, it's great! You keep on using it. But meanwhile the trojan may also install a permanent keylogger that now tracks every keystroke you make and sends it off over the internet to whomever created the trojan. Beware of free gifts! as the Greeks found out in the story of the Trojan Horse.
Beware of free gifts!


A computer worm is a computer program that makes lots of copies of itself, like a computer virus. The main difference between the two is that a computer virus attaches itself to another computer program, but a worm works by itself. As well as copying itself, a worm can be made to do all sorts of things, like delete files on a computer, or send e-mails to everyone the owner has in their address book.

logic bomb

A logic bomb is a virus program designed to attack in response to a particular logical event or sequence of events. It is a type of software sabotage, which is a malicious attack on work, tools or business.
For example, an attacker plants a logic bomb to destroy computer data files or information. It might be triggered when a certain user accesses to a personal database field, such as log in.


A platform is some sort of hardware architecture and software framework that allows running.