2.1.1 System Fundamentals

What you should know technically


  • key terms—data, information, hardware components, for example, input devices, output devices, processing, storage, memory (RAM, ROM), MHz, dpi, bit, KB, MB, GB, TB, ASCII, compatibility, OCR, OMR, bar code, baud, verification and validation, encryption/decryption, firewall, virus, Trojan horse, worm, logic bomb, platform, peripheral
  • use, advantages and disadvantages of analogue and digital data
  • operating systems (multitasking, boot) and utilities, for example, defragment, disk format, virus scan programs
  • responsible computer use (for example, regular back-ups, virus checking, security, storage, housekeeping)
  • a responsible and systematic approach to implementing or upgrading IT systems, for example, analysis, design, implementation, testing, evaluation, training, policies and standards.


The Social and Ethical Issues


Key Terms

Here you can update and revise the definitions and add links to resources that explain in more detail:

Data and 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.

Input/Output and Storage Devices


An input device is any piece of hardware which is used to enter data or content into a computer system. Input devices are usually categoried as either manual or automatic. Examples of manual input devices are the keyboard, mouse and scanner. Examples of automatic input devices are MICR, Barcode readers, OMR.

click here for //www.teach-ICT.com// notes: //Input// Devices,

In computing terms, an output device is a piece of hardware that obeys a computer command to do something in the real world. For example a printer is an output device that will produce a page page of information when the correct commands are sent to it from a computer.


processing

ASCII

compatibility

OCR

OMR

bar code

baud

platform

peripheral


Storage devices including memory (RAM, ROM)

All data within the computer is held in 'memory' of one kind or another. The two types of storage for program control are:
  • Hard Disk - vast storage but relatively slow
  • 'Volatile memory - RAM - Used to store data that the CPU requires to run an application.
*
In general, the more RAM that is installed in the machine the better its performance.

ROM is a special kind of memory which stores the instructions which the computer uses when it
ROM
ROM
'boots up' - the BIOS (basic input output system). It allows it to check the type of hard disk installed, the amount of RAM installed (see next page), the type of CPU being used etc.

Because the data is 'read only', it can be read but not changed by the user.
ROM
ROM
The ROM chip (although there may be more than one) is attached to the Motherboard.

The key thing to remember about ROM is that the data is not erased when the computer is switched off - the data is stored permenantly. This type of memory is called 'non volatile memory'


See mini-sites in //www.teach-ICT.com//: GCSE version,


MHz

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.

dpi

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.

Bit

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.

KB

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.

MB

It 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.

GB

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

TB

(terabyte) 1,024 GB.his used to be a very obscure term because there was very little use for it. But now storage devices are becoming so vast that Terabyte hard disks are becoming available and so the word is appearing more and more when talking about storage


Verification and Validation

Verification means to check the data that you have entered against the original source data. For example, entering a password and then re-entering the password.

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

encryption/decryption


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.

firewall

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.

Geeks To You Firewall Diagram - Home Computer Security
Geeks To You Firewall Diagram - Home Computer Security

Computer Virus



Test Yourself


Here are some revision resources that I have found online from other ITGS sites:
Key terms quiz (thanks to Osaka International School ITGS website for this resource)