Unit 30 Digital GraphicsUnit 30 Digital GraphicsBTEC Level 3BTEC Level 3

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Anne Sewell

ObjectivesObjectives

Computer Hardware Components of a Computer Types of computer The Processor – CPU Input and output devices Types of memory Embedded & special purpose computers

Chapter 1 Chapter 1 Computer HardwareComputer Hardware

Computer Systems– Consists of Hardware & Software

Hardware – physical machinery or components Software – computer programs (sequences of

instructions) telling computer what to do

Components of a ComputerComponents of a Computer

Types of computerTypes of computer Computers can be categorised into four types Microcomputers

– desktop, laptop, notebook and palmtop personal computers (PCs)– used in businesses, schools/colleges, hospitals, booking systems

and home– range in price from a few hundred pounds to a few thousand

Minicomputers– often used as multi-user systems, with hundreds of workstations or

terminals attached to a central minicomputer, e.g. EPOS. – Cost from £10,000 to about £150,000.

Mainframe computers– used by large organisations – may have thousands of terminals, often remote. – Cost ££ hundreds of thousands

Supercomputers– Largest category of computer– used mostly by scientific and industrial research departments,

NASA, the Weather centre,stock exchanges. – Cost ££ millions

The Processor - CPUThe Processor - CPU

controls the transmission of data from input devices to memory

processes the data held in main memory controls the transmission of information from main memory

to output devices

The CPU in a microcomputer is called a MICROPROCESSOR CPU and main memory of a computer are held on a mother

board CPU capability still doubling every 18 months

Input and output devicesInput and output devices

Input devices– keyboard– mouse– barcode readers – scanners

Output devices – printer– plotter– VDU

Main memoryMain memory

Instructions and data are held in main memory, which is divided into millions of individually-addressable storage units called bytes.

One byte can hold one character, or it can be used to hold a code representing, for example, a tiny part of a picture, a sound, or part of a computer program instruction.

The total number of bytes in main memory is referred to as the computer’s memory size.

Computer memory sizesComputer memory sizes

Memory sizes are measured as follows:

1 Kilobyte (Kb) = 1000 bytes (to be exact, 1024 bytes) 1 Megabyte (Mb) = 1,000,000 (1 million) bytes 1 Gigabyte (Gb) = 1,000,000,000 (1 billion) bytes 1 Terabyte (Tb) = 1,000,000,000,000 (1 trillion) bytes

RAM & ROMRAM & ROM

Random Access Memory (RAM) – ‘ordinary’ memory– used for storing programs which are currently running and data

which is being processed. – This type of memory is volatile - it loses all its contents as soon as

the machine is switched off.

Read Only Memory (ROM)– non-volatile, with contents permanently etched – used for example to hold the bootstrap loader, the program which

runs as soon as the computer is switched on and instructs it to load the operating system from disk into memory.

Cache memoryCache memory

very fast memory used to improve the speed of a computer, doubling it in some cases

acts as an intermediate store between the CPU and main memory

stores the most frequently or recently used instructions and data for rapid retrieval

generally between 1Kb and 512Kb

Auxiliary storageAuxiliary storage Hard disks

– all standalone PCs have in-built hard disk– typical capacity for Pentium PC is 5-10Gb – used for storing software including the operating system, other

systems software, application programs and data Floppy disks

– thin sheet of mylar plastic in hard 3½” casing – high density 1.44Mb

CD-ROM – holds about 650Mb

Zip disks

– hold up to 250Mb

Embedded & special purpose computersEmbedded & special purpose computers

Special purpose or dedicated computers perform wide variety of tasks e.g.

– Controlling temp. & humidity in a greenhouse– Controlling traffic lights & traffic flow– Controlling cashpoint machines

Embedded computers used widely in household goods, automobiles and industry

Special purpose computers still have same basic components of input, output, processor and memory as general purpose computers

– Programs etched permanently into memory.– Sometimes known as Firmware a combination of software and

hardware

Questions Questions

1. Describe the major improvement which have occurred in PC specifications during the last 5 years.

2. Look at an advert for a new PC and explain the key terms and abbreviations.

3. Name some alternative input devices and their uses.

4. A typical business micro. stores all its software and data files on hard disk. It also has a floppy disk drive. Outline 2 different reasons why the floppy disk may still be needed. (4)

5. In the context of a typical computer system state the purpose of:

1. Internal memory

2. External memory