COMPUTER Structure

Int 2 Unit 1 – Computer Int 2 Unit 1 – Computer SystemsSystems

St Kentigern’s AcademySt Kentigern’s Academy

Computer Structure• Represent the structure of a computer in the form of a

simple five box diagram representing:– Input devices– Processor– Main memory– Output devices– Backing storage

• Describe purpose of a processor

• List the parts of a processor as ALU, control unit and registers

• Distinguish between main memory and backing storage

Computer Structure• Describe the features of ROM and RAM

• Describe the uses of embedded, palmtop, laptop, desktop and mainframe computers

• Compare the features of embedded, palmtop, laptop, desktop and mainframe computers:– Type and speed of processor– Size of main memory– Backing storage– Input and output devices

• Describe clock speed as a simple indicator of system performance

Input - Process - Output

Input Device

Output DeviceCPU

Backing Storage

• Computer Hardware is the physical parts of the computer.

• The parts that we can physically touch, even if they are inside the case.

Computer Hardware

• There is obvious hardware – the bits we can see – such as the monitor, mouse, keyboard etc.

• But there are other pieces of hardware inside the “box”, e.g. the memory, hard disk, motherboard etc.

Computer Hardware

Central Processing Unit

Processor

Arithmetic & Logic Unit

Registers

Control Unit

Main Memory

Random Access Memory (RAM)

Read Only Memory (ROM)

Processor

• The processor is the hardware inside the CPU that controls the operation of the computer – It could be said the processor is the computers brain.

• Within the processor are the– Control unit– Arithmetic and logic unit (ALU)– Registers

Arithmetic and Logic Unit

• Arithmetic and Logic Unit– The main functions of the ALU are:

• To perform arithmetic calculations (addition, subtraction, multiplication, division)

• To perform logic functions involving branching, e.g. IF…THEN

Registers

• Registers– These are temporary storage areas

within the processor that are used to hold data that has been fetched from the memory or produced during a calculation

Control Unit• Control Unit

– The main functions of the control unit are:• To control the timing of operations withing the

processor

• To send out signals that fetch instructions from the main memory

• To interpret these instructions

• To carry out instructions that are fetched from the main memory

– In general the control unit is responsible for the running of the programs that are loaded into the main memory.

• Speed of the processor– The faster that a processor can perform

these calculations the faster the computer will be.

– A processor is measured in Giga Hertz(GHz).

Processor

– Two processors have the same 10 calculations to perform.

– One of the processors has a speed of 2.8GHz and the other 2.4GHz.

– Which processor will complete the task first?

Processor

• Main Memory– When the computer is working all the

programs and data that it is using are stored in memory.

– There are two types of memory• Random Access Memory (RAM); &

• Read Only Memory (ROM).

Main Memory

• Random Access Memory (RAM)

– This is where your programs and files are stored while you are using them.

– When you load a file it goes into RAM.

Main memory

– This kind of memory can be read from and written to.• Data is stored in RAM when it has been

loaded from backing store or when the user is entering it.

– When the computer is switched off, all data stored in RAM is lost.• This is why we use backing storage to keep

programs and data when they are not being used.

Main Memory

– You are playing your playstation.

– You load a game from a cd (backing store).

– It goes into your playstations RAM.

– If you don’t save to your memory stick and switch the computer off.

– What happens to the game you are playing?

Main Memory

• Read Only Memory (ROM)– ROM stores the bootstrap loader.

– This is used to locate the operating system which is stored on the hard disk.

Main memory

• Read Only Memory (ROM)

– This kind of memory can only be read from. • The data in ROM cannot be changed or

added to.

– When the computer is switched off, all data stored in ROM is saved.

Main memory

Main Memory v’s Backing Store

• Backing Storage– Examples of this are floppy

disks, flash drives, hard drives, CD, etc.

– By saving files and programs onto backing storage they will still be there even after the computer is switched off

• Main memory is not as large as backing storage devices

BACKING STORAGEDEVICES

Rom and Ram • The main memory is composed of ROM and RAM.

• ROM has the following features

– Data in ROM is permanently etched onto a microchip

– ROM is read-only so it cannot be changed

– Data on ROM is not lost when the computer is switched off

• RAM has the following features:

– The data in RAM is read/write so it can be changed

– All data stored in RAM is lost when the computer is switched off

– RAM is sometimes referred to as primary storage

Embedded System• Embedded Systems

– A combination of hardware and software to perform a specific function

•interactive game consoles, •elevators•computerised fridges

Palmtop System• Palmtop

– Simple version of basic computer application, web browsing and email, maybe a cellular phone connection.

– Usually uses a touch screen and stylus for data entry

Laptop System• Laptop

– Mainly used as a portable computer system between the user’s place of work and home.

Desktop System

• Desktop– This is a computer system that can fit on

your desk at home, work, school or college.

– Some users need a general-purpose desktop computer to run a range off applications; others need a desktop computer that will form a workstation on a network.

Mainframe System

• Mainframe computers– Used by large companies, such as banks and

insurance companies to allow remote access to the processor which is held in a central location.

– Their processor is very powerful as huge amounts of data is dealt with.

Embedded Palmtop Laptop Desktop Mainframe Computers

Processor Power

Up to 60 Mhz 200-500 MHz 2.4 GHz 3.2 GHz Several processors

Memory Size

1 bit – 512Mb +

64 Mb 512 Mb 256 MB 32Gb memory

Backing Store

•none•Flash memory

•RAM so a constant current has to be applied.•Additional backing storage can be purchased

•40 Gb hard drive•Removable 3.5” floppy drive•A combination 8x DVD-ROM and 8x/4x/24x CD-RW drive

•Large capacity hard-disk•CD-ROM/DVD drive

•100Gb hard disk•Tape drive

Input Devices

Field probes/sensors, keyboards, microphone, wands, disk heads, strain gauges

•Touch screen•Voice input•Keyboard•Infrared receiver•Modem

•Touch pad•Keyboard

•Microphone•Webcam•Graphics tablet•Scanner•Joystick

Keyboard

OutputDevices

Speakers, projectors, network cables, disk heads, impact printers, card punches

•LCD screen•a speaker•Infrared transmitter•Wireless connection

•LCD screen•Speakers•Infrared transmitter•Modem NIC•USB or Firewire interface

•Inkjet/laser printer•17” monitor•Speakers•Modem•NIC

•Line printers•Page printers•monitors