jess+pior

omg i gotta get 20 marks for project1a !!!!! help

my course is due in next friday!!!!!!!!!!! need to spend 50 mins on it !!!!!!!!











__revision for exams__ __ notes on networks __

__ output devices __
 * networks were made to link computers together so that they could share files.
 * if your computer is not connected to a network it is known as "stand-alone".
 * if a computer is connected to a network its known as "work-station".
 * in a school or office all the computers link to one printer because its cheaper.
 * a network also allows you to connect to a software or data.
 * if computers are connected from across the road or are fairly close they can be connected wirelessly or through cables this stands for LAN (local area network)
 * when the computers are connected users can use the same resources at the same time:software ,hard drive, printers and files.
 * users can also use LAN to communicate by email.
 * file servers are often used to store each persons data which means any user can log on to any computer and look at anyones files aslo it is easy to make a back up.
 * it would not be possible to connect computers in birmingham with ones in london using LAN cables
 * LAN is used to connect 1 building to another building which is usually through a telephone system using a modem they can also connect through microwave links satellite or fibre optic cables.
 * if you link LANs together they create a wide area network not a LAN but a WAN.
 * the largest WAN in exsistance is the interent.


 * TFT monitors (film transistor monitors) are replacing CRT monitors they look nicer, make less heat, take up less space but are easy to damage and not as good quality pics as CRT.
 * CRT monitors (cathode ray tube) are the noisest,produces most heat, bulky but are really hard to damage.
 * monitors are the most common output device.
 * pictures are made up of tiny dots called pixels the higher the number the better quality.
 * printers used to make hard copies of work
 * dot matrix best to use if making carbon copies of work, not so common anymore, also known as impact printers good for billing and invoicing
 * plotter printers best for architecture engineering and map making some plotters print by using pen which draws lines to create pictures also plotters which are "pen-less" for high quality density drawings 3 types of plotters- flatbed which holds the paper still while the pen goes over the paper drum- which rolls the paper over a cylinder and pinch roller which is a mixture between flatbed and drum
 * ink jet printers most popular,cheap,combine black and white with colour at the same time and are used in homes because not the best quality.
 * laser printers used in offices,quick,quiet,high quality black and white lasers are cheaper than colour.
 * speakers can tell you if you have made an error or mistake if fitted with an internal speaker advantages- everyone can hear the output helpful to accompany or create an atmosphere to a presentation help blind people to use the computer.disadvantages - can disturb others, high quality external speakers are expensive
 * lights LEDs ( light emitting diodes) can be connected to the computer which respond to eletric signals telling the lights to switch on or of. advantages - range of colours can give warning if a person is deaf and cant hear the bleeping help provide evidnece computer is working right. disadvantages- bulb can break/ wear out so needs to be replaced might loose connection so the light switch wont work even if the circuit is right.

__ input devices __
 * keyboards most common input device. they can cause strain also a concept keyboard uses pictures instead of letters
 * a mouse is a "pionting device"
 * flatbed scanners are also known as handheld
 * light pens are used to select different things
 * MICR is used for reading cheques
 * sound is detected from electric signals then transmitted to the computer this is a microphone.
 * touchscreens are used in building societies musems and airports.
 * graphic tablet is used to make precise drawings

storage devices

__virus's__
 * a bit is the smallest unit of storage it is made up of a binary digit
 * RAM is volatile memory
 * ROM is non volatile memory and stores computer start up instructions called BIOS
 * the amount of RAM usually stored on a computer is 1 gigayte
 * the hardisk in your computer is not an optical storing device it stores regulary used applications a hard disk installed in a computer would be 120 gigabytes
 * a magnetic tape has a magnetic device with a serial access
 * a floppy disk is a magnetic storage device and can store up to 1.44 megabytes
 * a zip disk is not an optical storing device and usually are already in the computer and dont have to be installed
 * if you want to save files over and over again you use CD-RW
 * a DVD is an optical storage device.
 * smallest to largest units of storage
 * bit
 * byte
 * kilobyte
 * megabyte
 * gigabyte
 * terabyte.
 * a virus is software that copies itself over and over again and attaches itself to programmes
 * there are virus's that are really nasty that delete all your files
 * viruses dont effect your hardware but your data and programmes