BASIC ORGANISATION OF COMPUTER

CONTROL MEMORY ALU OUTPUTINPUT 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

Hardware The physical components present in the computer. Software It 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 SECONDARY PRIMARY 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 Access Magnetic 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 Access Hard 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.