(Micro-computer)

Hardware

Keyboard Used to input data into the computer Advantage They are very common; all computers have one and they are easy to use. Disadvantage Easy to make mistakes if you can’t type quickly. Concept Keyboard A pictorial keyboard which you can press. Advantage Easy to use and waterproof Disadvantage The screen can get dirty. Might need to change the pictures if your stock changes

Mouse Enables you to control the movement of the on screen curser by moving it around a surface Advantage Easy to learn to use Accurate for selecting things Disadvantage Need a flat space next to the computer. Tracker Ball Like an upside down mouse, you turn it with your hand to move the pointer on the screen Advantage Ideal for using when flat space next to computer is limited Disadvantage Not supplied as standard.

Joystick Similar to a tracker ball in operation except you have a stick which is moved rather than a rolling ball. Advantage Immediate feel of direction. Disadvantage Some people find them more difficult to use than mice. Microphone Used to input sound Advantages Some systems can understand most peoples voices with voice recognition software Disadvantages Some systems need to be trained to understand each different voice.

Digital Camera Looks very similar to a traditional camera. However, unlike photographic cameras, digital cameras do not use film Advantage No film needed. Images can be digitally manipulated Disadvantage Need to print out photographs Scanner Another way in which we can capture still images or text to be stored and used on a computer. Advantage Can input things from paper documents With OCR software, text can be scanned in Disadvantage Images can take up a lot of memory space.

Graphics tablet Produces much more accurate drawings on the screen than a mouse or a pointing device could. Advantage Effective method of creating or changing diagrams and images. Disadvantage Only useful for inputting data about diagrams. Can be very sensitive to movement and difficult to get used to using

MICR Stands for Magnetic Ink Character Recognition. Banks use them; the reader reads the numbers on a cheque. Advantage Read at 100% accuracy.. Disadvantage The reader and ink is expensive OMR Stands for Optical Mark Reader. Reads pencil marks on a specially designed form or document, e.g. on a lottery ticket. Advantage Fast and accurate way of inputting information. Disadvantage Only works if the marks have been made accurately and clearly.

OCR Stands for Optical Character Recognition. It enables the computer to identify written or printed characters which have been scanned in. Advantage 95% accurate Disadvantage Needs careful checking as letters can be misread. Barcode Reader A bar code reader uses a visible red light to scan and read the barcode. The reflected light is translated into digital data that is interpreted by the computer and the correct price and product information is displayed. Advantage Any price change only needs to be changed on the computer system, not on each item.

Magnetic Stripe Build into back of plastic cards, e.g. identity cards or credit cards. Holds information about the card owner. Advantage Simple to use and cheap to produce. Disadvantage Limited storage capacity – only 60 characters. Sensors Sensors are used to detect physical quantities outside a computer such as temperature, pressure and light. To be able to process input from sensors a device called an analogue to digital converter must be connected between the computer and the sensors. This device converts signals from sensors into digital data that the computer can process

 Once the computer has processed all the information from the inputs then it must display or output the information in some way.  This is when we use Output devices that enable us to see or hear the information stored in the computer.

There are many different Output devices but the most commonly used are: 1. Monitors 2. Printers 3. Speakers / Headphones 4. Lights 5. Plotters

 Monitors display the information on a screen.  You can get 2 main types of monitors: CRT’s: Cathode Ray Tube monitors are fairly large and they are not as common as LCD’s nowadays. CRT’s work by using an electron gun situated at the end of the tube. LCD’s: Liquid Crystal Display monitors are thin and are more commonly used. They work by using electronically charged crystals.

 There are 3 types of Printers: Dot Matrix : This printer is the oldest of the three and is not used much now because it doesn’t give as good results as the other two. It uses Carbon ribbon and pins. Ink Jets : This printer has become cheaper and is commonly used at home as they are perfect for small quantities of work. The ink jets use ink cartridges that are heated up and droplets are then dropped on to the paper forming a small part of the overall image. Laser : This printer is more expensive that the others however it is excellent for use in work as it is quiet, quick, can be stocked with a lot of paper and produces high-quality work.

 These devices produce high quality lines diagrams on paper. Architects, Engineers and Scientist often use plotters.  The plotter uses a pen that can be lifted on and off the paper which is how this dev

 There is usually a small speaker within the computer however to increase the volume and quality of the sound we plug in external speakers which allow us to hear the music better.  Headphones can be plugged into almost all computers and they enable you to listen to your music without disturbing others.

 These are known as LED’s (light emitting diodes) and they are useful in presentations and also for situations like when a computer is controlling traffic lights.  LED’s last approx. 100,000 hours and they can either be dim or very bright.

Unless you want to lose all of the work you have done on your computer, you need to have a way to store it safely. There are various types of storage devices, different devices are suitable for different tasks. We will be looking at the main ones which you need to know about.

Hardware is the name given to any part of a computer that you can touch ~*~ An individual piece of hardware is called a device

The main memory of a computer is made up of a set of memory chips called ROM and RAM ~*~ ROM = Read Only Memory RAM = Random Access Memory

The instructions to start the computer are stored on this This sort of memory is non-volatile memory Programs and data stored on RAM are lost when a computer is switched off- This memory is volatile memory

Computer memory is measured in Bytes Byte = 8 bits Kilobyte = 1000 bytes Megabyte = 1000 kilobytes Gigabyte = 1000 Megabytes Bit = either 0 or 1 Units

 Main store ( memory storage in the computer) ~*~  Backing storage ( storage on disks tape CD etc)

Hard Disk Advantages Main Backing storage for files and programs Can store lots of data compared to the floppy disc Can have a second hard disk as Back-up storage Disadvantages Slow to access when compared to ram Data can Be damaged if the head crashes onto the platter Typical size = 120GB

Advantages  Small thin and lightweight so easy to carry round  Can Be reused But data cant Be overwritten only deleted to create space Disadvantages  Can’t store that much and one Big picture will take up a lot of room  It’s thin so it could get damaged easily Typical size = 1 · 44 MB

Zip Disc Advantages Can hold more data than a floppy disk and again easy to carry around Because of the size Disadvantages Much more expensive than a floppy You need a special drive to read the disk Typical size = 100 MB

Magnetic Tape Advantages Can store a lot of data Not easily damaged Can Be used overnight to Back up a system Disadvantages Takes a long time to load data onto it Have to go through the tape to get to the data you want – serial access Typical size = 100MB

CD-Rom Advantages Data cannot Be erased – you cannot lose your data Easy to carry around Cheap to produce Can Be read By a DVD drive Disadvantages Fragile Can scratch easily – this effects the data when the laser reads it Slower to access than a hard drive Typical size = 650mb

DVD Advantages large amount of storage Does not transmit virus’s The prices are getting cheaper Good for storing films Disadvantages Doesn't work in CD ROM drives More expensive than CD roms Typical size = 5- 17GB

 Data: raw numbers, words, collections of unprocessed stuff…  Information: the organization of data into meaningful and useful terms.

 In the world of computers, information is digital.  This information is made up of discrete units.  These discrete units are called: Bits.  Bit: (Binary digit) is the smallest unit of information a computer can process  Bits have only two values: 1 or 0

 A collection of 8 bits is called a byte.  Bytes are bigger than bits.  A nibble is half of a byte (4 bits, this term is obsolete). bit < nibble < byte

 A collection of 8 bits can represent 256 different messages: 2 8 = 256  By mixing and matching combinations of “On’s” and “Off’s” you can get 256 different messages.

 Binary Number System

= 0

= 1

= 2

= 3

= 255 Note: we get 256 possible characters because we start at 0 and go to 255 which is 256 separate numbers.

 ASCII (pronounced as-kee 2) is the most widely used code  To make words, sentences, and paragraphs fit into the computer’s binary- code circuitry, a unique piece of code was devised to represent each letter, digit, and special character as a unique string of bits.

 American Standard Code  Using only 8 bits ASCII has a set of 256 individual characters, for all letters (upper and lower case), numbers and some special characters  Unicode is possibly going to replace ASCII. Unicode has a 65,000 character set. This will be done by using 2 bytes (16 bits) per character.

 Bits can represent data stored on a computer.  A string of bits can also represent an instruction  could tell the CPU to add two numbers together.

 B, KB, MB, GB, TB, PB  Those abbreviations describe the capacity of memory & storage components.  Also quantify the size of computer file.  Mb ≠ MB

TermValue ByteA group of 8 bits. K (kilobyte) also KB About 1000 bytes of information. Technically 1K is 1024, because 1024 is 2 10 MB (megabyte)Approximately 1000K, or 1 million bytes GB (gigabyte)Approximately 1000MB TB (terabyte)Approximately 1 million megabytes.