Components of a computer systemComponents of a computer system

HardwareHardware

Central Processing Unit (CPU)Central Processing Unit (CPU)

MemoryMemory

Input and Output DevicesInput and Output Devices

SoftwareSoftware

DataData

Components of a computer systemComponents of a computer system

• Computer hardware provides the physical Computer hardware provides the physical

mechanisms to store, manipulate and input mechanisms to store, manipulate and input /output data./output data.

• Software provides instructions to tell the Software provides instructions to tell the hardware what tasks to performhardware what tasks to perform

• Data in the computer may be representing Data in the computer may be representing numbers, characters, graphics etc but is numbers, characters, graphics etc but is always kept in a form that the hardware and always kept in a form that the hardware and software can manipulate. software can manipulate.

Basic concepts - Hardware Basic concepts - Hardware

• CPU performs actual processing of data. CPU performs actual processing of data.

• Data and programs are stored in memory, Data and programs are stored in memory, and moved to and from CPU as required.and moved to and from CPU as required.

• Data travels between system components Data travels between system components along electronic pathways, (sets of wires), along electronic pathways, (sets of wires), called buses.called buses.

We will look at: We will look at:

Four Box diagramFour Box diagram CPUCPU MemoryMemory Registers and Registers and

their roletheir role Processing speedProcessing speed

Three major components of the Three major components of the CPUCPU: : ALUALU, , Control Control unit and Registersunit and Registers. .

The The Arithmetic Logic UnitArithmetic Logic Unit (ALU) operates on binary (ALU) operates on binary data to perform all arithmetic and logical functions. data to perform all arithmetic and logical functions.

+ - * / + - * / < > = <> < > = <> AND OR NOT AND OR NOT Rotate ShiftRotate Shift

Control unitControl unit fetches and interprets instructions in fetches and interprets instructions in memory and generates signals to control all other memory and generates signals to control all other system components.system components.

Four Box DiagramFour Box Diagram

Input Output

Backing Store

ProcessorMemory

(RAM and ROM)

CPU

MemoryMemory Purpose of memory is data storage. Purpose of memory is data storage. A hierarchy of memory exists .A hierarchy of memory exists .

data required for immediate data required for immediate manipulation by CPU is stored manipulation by CPU is stored in small areas of fast access in small areas of fast access memory within CPU calledmemory within CPU called registersregisters..

data required for active data required for active program is generally stored in program is generally stored in primary memory, commonly primary memory, commonly called called RAM.RAM.

data which may be required at data which may be required at later time generally stored in later time generally stored in secondary storage e.g. on disk, secondary storage e.g. on disk, tape, or CD-Rom.tape, or CD-Rom.

Memory: characteristicsMemory: characteristics

CapacityCapacity : no of bits, bytes or words : no of bits, bytes or words in module. Addressable unit - 1 word . in module. Addressable unit - 1 word . Word size may be 8, 16, 32 bits ; (1 Word size may be 8, 16, 32 bits ; (1 byte = 8 bits)byte = 8 bits)

Unit of transferUnit of transfer : RAM = 1 word ; Disk : RAM = 1 word ; Disk = 1 block= 1 block

access time or speedaccess time or speed - time required - time required to read from memory location. to read from memory location. Tradeoff between quantity, cost and Tradeoff between quantity, cost and speed . As speed increases so does speed . As speed increases so does cost. cost.

Also know as Primary StorageAlso know as Primary Storage

RegistersRegisters: very fast memory : very fast memory internal to CPU providing internal to CPU providing temporary storage places for temporary storage places for data being manipulated.data being manipulated.

System clockSystem clock generates generates regular pulses to synchronize regular pulses to synchronize all system events and all system events and determine the speed at which determine the speed at which processing can occur. processing can occur.

Basic measure of system Basic measure of system performance is clock speed, performance is clock speed, measured in megahertz measured in megahertz (millions of cycles per second) (millions of cycles per second)

Semiconductor main memorySemiconductor main memory

Primary memory is made up of RAM and ROM is made up of RAM and ROM

Types include:Types include: RAM (Random Access Memory)RAM (Random Access Memory) ROM (Read Only Memory)ROM (Read Only Memory)

ROM- SECONDARY STORAGEROM- SECONDARY STORAGE

Read Only MemoryRead Only Memory

•Permanent non-volatilePermanent non-volatile

•Software and data fixed Software and data fixed during chip manufactureduring chip manufacture

•Cannot be written toCannot be written to

•All computers have some All computers have some ROM to load the Operating ROM to load the Operating System into RAM System into RAM (bootstrap loader) (bootstrap loader)

ALU

ControlUnit

CPU

PrimaryMemory

– CPU exchanges data with memory via

the registers such as IR and PC.

RegistersSecondaryMemoryi.e. hard driveCD R/WFloppy

How the components interact

InputsInputs

Input Devices include:Input Devices include:

KeyboardsKeyboards

Mouse (Mice)Mouse (Mice)

MicrophonesMicrophones

WebcamsWebcams

Graphics TabletGraphics Tablet

OutputOutput

PrintersPrinters

MonitorMonitor

SpeakersSpeakers