TRANSISTOR

Transistor is an electronic device which helps to amplify input signal to produce high output signal. It is made from semi-conductor materials. It consists of three materials as Emitter, collector and base. It is used in circuit to amplify video signal, voltage signal etc.It is of two types NPN transistor and PNP transistor.

NPN transistor has p type semi conductor material sandwiched between N type semi-conductor materials from both side whereas IN PNP transistor N type semi-conductor material is sandwiched between P type semi-conductor materials from both side. It is used in monitor circuit, sound box (speaker), motherboard, printer etc.

MOUSE

Mouse is a small hand held devices used to position the cursor on the screen. A selection can be made from a displayed menu by positioning the cursor over the required selection by the movement of mouse and pressing a button on the mouse to indicate that this is the selection required. Mouse can be moved over other graphical component such as button, combo box, list box etc. and mouse button can be pressed to activate various control. They can be used in art and design work. There are 3 types of mouse. There are given below:

1) Mechanical mouse

2) Optical mouse

3) Optomechanical mouse

MONITER

A monitor is a softcopy output device that displays the data, instruction, and result of processing or other information. It looks like a television. The output displayed on the monitor is called the softcopy. The most of the monitor is made up of Cathode Ray Tube (CRT). A CRT is an evacuated glass tube with an election gun in its neck and a fluorescent coated surface opposite the electron gun. The display screen of CRT monitor is covered with tiny phosphor dots which are called pixels (picture elements). The pixels on the monitor form images. So, more the number of pixels better the display quality.

CRT monitor can be monochrome or color. A monochrome monitor can display texts or images only in two colors (black and white colors). A color monitor displays texts or images in millions of colors.

Nowadays Liquid Crystal Display (LCD) monitors are mostly used instead of CRT monitors. The LCD monitors are the flat panel monitors which use special kind of liquid crystal to form images. The LCD monitor can display pictures, text and videos more clearly than the CRT based monitors. Since LCD monitors consume lesser amount of electricity than CRT monitors, they are used in notebooks and laptop computers. LCD monitors are also used in desktop computers. The display on the monitor is controlled by an adapter, display card or video card. The display cards may be SVGA(super video graphics array) or AGP (Accelerated Graphic Port).

HARD DISK

Hard disk is a type of secondary memory which is used to store data for permanent time period. It can store data in the form of magnetic flux. Hard disk is consists of a circular plate known as platter which was made of aluminum glass or plastic. Both surface disk plate is coated with metallic oxide. The disk plate is fixed on a motor which rotates disk plate. For each platter there are two heads (upper surface and other for lower one0. Both heads are fixed on a head arm which is controlled by head actuator. The surface of this plate contains number of circle known as tracks. Section of tracks is known as sector. In hard disk data is stored from outer track to inner one. The read/write heads leaner magnetic flux one the disk plate. The read/write head acts as a magnet which leaves data signals in the form of magnetic charge.

MEMORY

Memory is a unit area where small size as well as large amount of data can be stored for temporary or permanent time period. Some types of memory store data without using any power backup and some type of memory require power supply. Similarly some memories are essential to run computer system while others are required for only data storing depending on their nature. Memory is classified into two types. Those are:

1)    Primarymemory:                                                                                                                                                                                   They are essential memory to run a computer system which store small size of data temporary period with the help of power backup. Those types of memories are required while booting the computer system. If the power supply is stopped all the data stored in primary memory are lost. So, these types of memories are called primary memory. For example: RAM and ROM.

2)    Secondarymemory:                                                                                                                                                                              Those memories which are used to store data and programmes for further use i.e. for permanent time period without any power backup. Those types of memories are not essential to run computer system. So, they are called secondary memory or auxiliary memory. For example: Hard-disk (HDD), Pen drive etc.

KEYBOARD

 Keyboard is an input device which is used to input different commands, instructions and values. It is used for executing, entering and for selection purpose. It consist number of keys for different functions. A standard keyboard has 102 key while multimedia keyboard has more number of keys. It has numeric function keys, printing keys and non-printing keys. All keyboard have common working principle. But the architecture can be different. It consist of 3 plastic layers which have two (first and last)circuits while other  has holes on it. When any key is pressed the spring or rubber membrane stroke on the dot of circuit.hence, current signs flow through the circuit. All signal passes to the IC if keyboard and is further sent to the CPU

MOTHERBOARD

Motherboard is a largest circuit board found in computer system which provides platform to connect a various types of I/O devices as well as processor and memory. It is a backbone which helps to interact various devices with each other. It is a printed circuit board having complex electrical components. Such as capacitor, diode, IC, transistor, chips etc. It is also having various slots and sockets where I/O devices, RAM and processor are kept. It has two main chips on near the processor is called north bridge chip, on other far from the processor is called south bridge chips. North Bridge Chips links data flow between processor and RAM whereas South Bridge Chips links data flow between PCI devices and RAM. It has a small chips known as CMOS Chips and 3 volt DC battery for CMOS power backup. 

PROCESSOR

Processor is a core component of computer system. It helps to process data instruction and execute (run) programs. It is small chip which is made of thousand of transistor. It consists of very complex microscopic circuit fabilicate on a chip. The shape and size of processor varies according to generation and model of computer. Some processors have pins on their surface while other don’t have pins on their surface. Some processor are placed in socket of motherboard while other in slot. Processor is of two types socket type and slot type. Pentium I to Pentium III processor have pins on their surface and are placed in socket with holes while Pentium IV processor are pin less and they are placed in socket with pins. Some of Pentium II and Pentium III processor are card shape, so they are placed in slot.

RANDOM ACCESS MEMORY(RAM)

RAM is the type of primary memory which is requires to run computer system. Once computer is turn on RAM is started to functioning data and programs from hard disk are loaded into RAM and from RAM. Processors process one by one. All this process is carried until RAM get power on while the power is switch off the data. Instructions are lost.Since, the access data are store in memory location in random manner. So it is called RAM. It is of two types:-

1) STATIC RAM:                                                                                                                                       It is type of RAM which is found in Pentium I, Pentium II and Pentium III computer. It has double notch and 1 to 168 numbers of pins for signal transmission.Since, it updates data and instruction store in after a long time. The process data and instruction are appeared in RAM for a long time. So, it is called Static RAM.

2)DYNAMIC RAM:-

It is found in Pentium IV computer which has one notch and 1 to 240 pins.it has high frequency rate than Static RAM. It is of two types:-                                                                                                        i)DDR1 RAM                                                                           ii)DDR2 RAM

                                                                                                                                                                                                                                                                                                                                                                                      

READ ONLY MEMORY(ROM)

ROM is also called CMOS (Complementary Metal Oxide Semiconductor) chip. It is an internal memory of a computer which is on a motherboard. It contains BIOS (Basic Input Output System) program which is a bridge between motherboard and operating system. The basic program stored in ROM is called Firmware. The motherboard manufacturer stores the firmware in ROM at the time of manufacturing motherboard. The firmware stored in ROM can only be read by the CPU but can’t be erased or rewritten. so it is called Read Only Memory(ROM).Except the BIOS program,a computer  needs information of devices like keyboard,mouse,hard disk.ram etc each and every time when it is turned on. So, these essential or necessary information are also stored in ROM chip later by the users themselves. These information are not erased when you turned off a computer. Since the program and data stored in ROM do not get erased when the computer is turned off. So it is also called permanent memory or non volatile memory. There are three types of memory:-  
                    
I)PROM(Programmable Read Only Memory)    

II)EPROM(Erasable Programmable Read Only Memory)                                                                     
                                                                                                                                                                        

III)EEPROM(Electrically Erasable Programmable Read Only Memory)

COMPUTER

Computer is derived for latin word “computare” which means “calculate”. In another way computer can defined as an electronic digital and automatic machine which takes input from the user , process it, stores it if necessary and gives output in desired form. Every computer system requires data and instructions to produce useful information. A computer system gets data and instruction through peripheral devices like keyboard, mouse, etc. in the same way the information from the computer are displayed to users through peripheral devices like monitor. All the hardware devices connected to a computer are known as peripheral devices. They are also known as I/O devices (Input/output Devices).A Computer consists of main processing unit called central processing unit (CPU) or processor (or microprocessor), main memory(normally RAM), input devices(normally keyboard, mouse), output device(normally monitor, printer) and auxiliary storage (normally hard disk, floppy disk).