A Description of Computers

Topics: Computer, Personal computer, Operating system Pages: 6 (1084 words) Published: November 20, 2013
Data
Bit- each individual ‘1’ or ‘0’ is a bit-short for binary digit. Byte- 8 bits are a byte.
Kilobyte-is 1000 bytes (1024)
Megabyte-is 1,000,000 bytes
Gigabyte-is 1,000,000,000 bytes
Each character on keyboard-8 bit

Computer systems v Manual systems
Benefits of computer system:
Takes up less space
Searching is very quick
More than one person can access the same data form their network PC. The data stays in the computers memory
Fewer staff are needed to look after a computer system
Reports can be generated very quickly-automated

Problems of a computer system:
Setting up is very expensive
Computer systems need people to maintain them
POWER CUTS!
It is easy to hack into a computer system.

Types of computer
Mainframes-biggest
They are the most powerful
They are very large
VERY expensive
They are used in BIG businesses-banks, insurance companies.

Minicomputers-middle
Less powerful than mainframe but more powerful than micros
Microcomputers-most common-usually called PC’s.
Are designed to stand alone
Much less powerful than mainframes.

Networks-LANS AND WANS
Local area network-LAN-small-offices and schools.
Wide area network-WAN-large-link together different places.

Advantage of using networks-peripherals such as printers can be shared amongst several users. Software can be shared amongst several users.
Communication across network is fast + cheap

Disadvantage of using networks-cabling can be expensive to install and replace A fault with the server will prevent the whole network from working Security measures are needed to restrict access to network

WANS are vulnerable to hackers and viruses.

'Networks-security
SERIAL NUMBERS
ALARMS
DOORS
FIRE PROTECTION
LOCK
AVOID
BLINDS

JUST REMEMBER SADFLAB
Passwords-should be changed frequently.
Backup-and files should be kept secure-in locked fireproof rooms.

Input devices
Keyboards
Mouses-touchpad, tracker balls.
Graphics pads make drawing easier and more accurate.
Joystick
Scanner
OCR scanners-read text
MICR-magnetic ink character recognition-cheques
OMR-optical mark recognition-registers-read lines in boxes.
Credit cards have a magnetic stripe on the back-carries info so the computer can identify the customer. The CPU
The control unit makes the system work-CU
It controls all hardware attached to the system.
It controls the output and input of data
It controls the flow of data within the CPU

The ALU is where the processing happens-Arithmetic and logic unit. Arithmetic part-does calculations!
Logic part-makes decisions like whether a number is bigger than –5.

The IAS is where active data is stored.
IAS-immediate access store

Output devices-PRINTERS
Dot matrix
Laser
Inkjet

Advantage of dot matrix-cheap and low operating costs.
Disadvantage of dot matrix-low res, slow, noisy.

Advantage of laser-high res, very fast
Disadvantage of laser-expensive.

Advantage of inkjet- good res, cheap
Disadvantage of inkjet- slow (ish), expensive to run

Data storage-ROM and RAM
RAM is temporary-random access memory
It stores data as electric signals.
If the power is cut or electricity fails everything in RAM-LOST! ROM is permanent-Read-only memory
ROM however is not a backing storage on hard disk.

Backing storage
Hard disk-main internal storage.
Large capacity-range from 20gb to 100gb!
Floppy disk-3.5 inch
1.44 mb-very small capacity
Magnetic tape-used to backup large amounts of data-cheap as well! Access time is slow because it has to run through whole disc to find something. Optical disks have fast access time.
CD-ROMS-oldest type-650mb
CD-R’s-sold as blanks-data can be written only once to it. CD-RW’s-most popular. RW stands for read and write.
DVD-17 gb
ZIP disks-larger, thicker-100mb

Operating systems
1. Enable applications to run
2. Enables software to communicate with systems hardware
3. It manages system resources
4. Monitors performance of system
5. Prompts error...
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