COMPUTER Structure Int 2 Unit 1 – Computer Systems St 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 Device CPU 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 –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 –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 –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 STORAGE DEVICES

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 , 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.

EmbeddedPalmtopLaptopDesktopMainframe Computers Processor Power Up to 60 Mhz MHz2.4 GHz3.2 GHzSeveral processors Memory Size 1 bit – 512Mb + 64 Mb512 Mb256 MB32Gb 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 Output Devices 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