BASIC ORGANISATION OF

COMPUTER

CONTROL

MEMORY

ALU

OUTPUTINPUT

Basic organisation of computer

Basic organisation of computer

• INPUT– The input unit is used to information or instruction

to the computer.– It accept the information or instruction from user

or from some where else.– Convert it to a computer understandable form and

send it to the computer.Eg:Keyboard,mouse,Joystick,MICR, etc,.

Basic organisation of computer (cont)

• CENTRAL PROCESSING UNIT (CPU)– It is the heart of the computer.– It performs all operations.– It contains the followings• CONTROL UNIT• ALU• MEMORY

Basic organisation of computer (cont)

• CONTROL UNIT– It controls all other units in the computer.– It directs the sequence in which operations to be

performed.– It also controls the flow of data between various

units.

Basic organisation of computer (cont)

• ARITHMETIC & LOGICAL UNIT

– It performs all arithmetic & logical operations.– i.e. arithmetic operations like addition,

subtraction, multiplication, division etc,. And logical operations like AND,OR,NOT etc,.

Basic organisation of computer (cont)

• MEMORY UNIT– Place for holding the information.– Types• Primary• Secondary

– Primary memory is used to store temporary data.Eg:RAM,ROM etc,.

– Secondary memory is used to store information permanently. Eg:Hard disk.

Basic organisation of computer

• OUTPUT– The output unit is used to display the result of the

process.Eg:Monitor,printer,speakers, etc,.

Components of Computers

Components of Computers

• HardwareThe physical components present in the

computer.

• SoftwareIt is a collection of programs and it can

perform some operaions.

Components Present inside the cabinet

• Motherboard• Processor• SMPS• Disk drives• RAM & ROM etc,.

Types of Memory

MEMORY

SECONDARYPRIMARY

RANDOM ACCESSSEQ.ACESS

• Primary Memory:It is used to store data temporary.

RAM• Random Access Memory• It is possible to randomly select and use any

location of the memory. • It is a volatile memories i.e. It loose their

content when the power is switched off

ROM• Read Only Memory • The data in the ROM is permanent . • It is a non-volatile memories i.e. It does not

loose their content when the power is switched off .

• Programmable Read Only Memory • It is supplied in blank by the manufacturer.• It is possible to store program in PROM chip.• Once the programmes are written it cannot be

changed and remain even if power is switched off.

PROM

• Erasable Programmable Read Only Memory.• Information stored in EPROM can be erased by

exposing the chip in ultraviolet light and it is reprogrammed using a special programming facility.

EPROM

• Electrically Erasable Programmable Read Only Memory.

• Information stored in EEPROM can be erased by applying some voltage.

EEPROM

• Secondary Memory:It is used to store data permanently

• TYPES: sequential access , random access

Sequential AccessMagnetic Tape: • Magnetic tapes are used by large computers

like mainframe computers where large volume of data is stored for a longer time.

• The cost of storing data in tapes is inexpensive.

• Tapes consist of magnetic materials that store data permanently.

Random AccessHard Disk:• It uses circular disk ,coated with magnetic

material called platters. • It rotates with very high speed inside the drive. • Data is stored on both the surface of the disk.• Each disk consists of a number of invisible

concentric circles called tracks. • The information stored in a disk can be read

many times without affecting the stored data.

Magnetic Hard Disk Mechanism

Random Access (cont)

Optical disk• It uses a circular plastic disk coated with

aluminium or silver storing data.• The data are stored in the circular tracks.• Laser beam is used for storing and retrieve

data from the disk

INPUT OUTPUT DEVICES

• Input Devices Input devices are necessary to convert

our information or data in to a form which can be understood by the computer.

• Eg: Keyboard, Mouse, MICR,OMR,OCR.

Keyboard

• This is the standard input device.• The layout of keyboard is just like the

traditional typewriter of the type QWERTY.• It also contains some extra command keys

and function keys. • The computer can recognise the electrical

signals corresponding to the correct key combination and processing is done accordingly

Mouse

• Mouse is an input device.• When the mouse is moved across a flat

surface the screen pointer is also moved in the direction of mouse movement.

• It is easier to move the cursor through a mouse

Magnetic Ink Character Recognition (MICR)

• This is widely used by banks to process large volumes of cheques and drafts.

• Cheques are put inside the MICR. • As they enter the reading unit ,the magnetic

field which causes the read head to recognise the character of the cheques.

Optical Mark Reader (OMR):

• This technique is used in objective type tests and the answer are marked by darkening a square or circular space by pencil or pen.

• These answer sheets are directly fed to a computer for grading where OMR is used.

Optical Character Recognition (OCR):

- It is used to recognize any printed character. - This characters are compared with patterns

stored inside the computer.- Whichever pattern is matched is called a

character read. - Patterns that cannot be identified are

rejected. OCRs are expensive though better the MICR.

Output Devices

Visual Display Unit

• The most popular output device is the Visual Display Unit (VDU).

• It is also called the monitor. • Monitor is used to display the input data and

to receive massages from the computer.• It can be color or monochrome.

Printer

• It is an important output device which can be used to get a printed copy of the processed text or result on paper.

• printers are classified as impact and non-impact printers.