Computer Hardware

UNIT-01

COMPUTER FUNDAMENTAL

Computer :-—Computer is an electronic device which receive the input (data) from the user, stored it for a long time as user required, process it according to the set of instruction (program) and give the result (output) into the output device.

Computer Hardware :-—A computer's hardware components are the parts you can touch. Computer hardware is the physical  part of the computer. The smallest hardware component of a computer is the computer chip. Example of computer hardware components are motherboard, CPU, RAM & hard disk drive etc.

Computer Software :-—Software is a collection of computer programs and related data that provides the instructions for telling a computer what to do and how to do it. Software includes all the various forms and roles that digitally stored data may have and play in a computer.

—There are basically three types of computer softwares.

1.System software.

2.Programming Software.

3.Application Software.

—System software-: System software is computer software designed to operate the computer hardware. System software includes device drivers, operating systems, servers, utilities, and window systems.

—Programming Software-: Programming software include tools in the form of programs or applications that software developers use to create, debug, maintain, or otherwise support other programs and applications, such as compilers, debuggers, interpreters, linkers, and text editors.

—Application Software-: Application software is developed to perform in any task that benefits from computation. It is a set of programs that allows the computer to perform a specific data processing job for the user.

Category of Hardware Components :-—Computer hardware components are divided into following categories.

1.Input Devices.

2.Output Devices.

3.Processing Devices.

4.Storage Devices.

5.Power Supply.

Input Devices :-—Input device are use to provide the data (input) to be processed by the computer. This data can be provided by different ways by the different input devices. There are following commonly used input devices.

—Keyboard.

—Mouse.

—Scanner.

—Microphone.

—Digital pan.

—Camera.

Output Devices :-—Output devices are use to provide the result (output) processed by the computer. This data can be provided by different ways by the different output devices. There are following commonly used output devices.

—Monitor.

—Printer.

—Speaker.

—Projector.

Processing Devices :-—These devices are used to process the data received from the input devices and provide the result  to the output devices. There are following devices helps to process the data.

—Motherboard.

—CPU (Central Processing Unit).

—RAM.

—BIOS (ROM).

              

Storage Devices :-—These devices are use to store the information or data in the computer. The storage devices store the user’s data and other important information required to process the other data. There are following main storage devices.

—Hard Disk Drive (HDD).

—Floppy Disk Drive (FDD).

—CD/DVD.

—Pen Drive.

—Flash Memory.

—Tape Drive.

Power Supply :-—Power supply is use to provide the power to all electronics components of the computer. SMPS (Switch Mode Power Supply) is used as a power supply in the computer. There is another power supply used in the computer for uninterrupted power supply called as UPS  (Uninterrupted Power Supply), but it is not main power supply.

UNIT-2 

Motherboard :-•The main circuit board of a microcomputer. The motherboard contains the connectors for attaching different components of the system. Typically, the motherboard contains the CPU,BIOS, memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers required to control standard peripheral devices, such as the display screen,keyboard, and disk drive. Collectively, all these chips that reside on the motherboard are known as the motherboard's chipset.

Modern motherboards include, at a minimum -:

1.Microprocessor Sockets/slots-:  in which microprocessor are connected .

2.Memory Slots-:  into which the system's main memory is to be installed.

3.Chipset-: which forms an interface between the CPU's front-side bus, main memory, and peripheral buses.

4.ROM/Non-volatile memory-: a  chips containing the system's firmware or BIOS.

5.Clock Generator-: It produces the system clock signal to synchronize the various components.

6.Expansion Slots-: These interface to the system via the buses supported by the chipset.

7.Power connectors-:  which receive electrical power from the computer power supply and distribute it to the CPU, chipset, main memory, and expansion cards.

 

Types Of Motherboard :-•Motherboards are classified as integrated and Non-integrated devices depending on the devices they support.

1.Integrated Motherboards.

2.Non-integrated Motherboards.

Integrated Motherboards :-•Integrated motherboards have all the peripheral device slots, input output ports, serial and parallel ports are mounted on the board. The connectors for the various devices such as the hard drive connector and floppy disk drive connector are installed directly on to the motherboard. The major disadvantage of these types of motherboards are that if an individual component of the motherboard fails, the whole board may need to be replaced and that can be a costly affair at times.

Non-integrated Motherboards :-•Non-Integrated motherboards have RAM slots integrated on the board. All the input-output ports for devices such as the serial and parallel port connectors, other controllers such as connectors for hard drive and floppy disk drives are attached to the system using expansionboards. Expansion boards use more space of the cabinet. Expansion boards use more spaceof the cabinet. If any one of the expansion boards fail, only those particular expansionsboard needs to be replaced and not the whole board.

Components of Motherboard :-•Components of motherboard are classified into following categories.

1.On board components.

2.Expansion Slots.

3.Connectors.

4.Input / Output Ports.

5.Jumpers.

On board components :-•There are following basic onboard components of motherboard.

1.CMOS Battery.

2.Real Time Clock Circuit (RTC).

3.BIOS Chip.

4.North Bridge.

5.South Bridge.

6.Input / Output Controller.

7.Audio Controller.

8.LAN Controller.

9.DMA (Direct Memory Access).

10.BIOS (Basic Input Output System).

•CMOS BATTERY-: It is used to provide the backup (Power backup) to the BIOS chip,which contain the configuration of date, time and other system configuration.

•REAL TIME CLOCK-: It provides the computer time and date update with the help of battery and BIOS.

•BIOS CHIP-:It is one of the most important programs stored in a ROM chip inside the computer. Basically it’s neither a complete H/W nor a complete S/W, so that it is called as“Firmware”.

•NORTH BRIDGE-: It is a main controller chip at motherboard that provides a connection between the microprocessor, RAM and AGP Slot. This chip is located near about of microprocessor’s socket on the motherboard.

•SOUTH BRIDGE-: It is also main control chip of motherboard like “North Bridge”. It provides a communication between the different motherboard’s components that are not supported by the North Bridge; such as I/O (Input/Output) controller, I/O Ports, expansion slots, motherboard connectors, BIOS and Graphics Controller.

•INPUT/OUTPUT CONTROLLER-: It is a controller chip that control all function of the I/O devices and handover them to the microprocessor.

•AUDIO CONTROLLER-: It is a chip that controls the audio signals given by the microprocessor as input or output signal.

•LAN CONTROLLER-: This chip control the network signals that are send or receive through the RJ-45 port.

•DMA-: It is a method of transferring information directly from external storage devices such as HDD, FDD and CD/DVD drive, Pen Drive into computer’s main memory (RAM) and vice-versa. During this process the information does not pass through the processor.When a large volume of data is to be transmitted between the processor and an external device, routing them through the processor is a very slow process. An additional device called DMA controller placed between the I/O device and memory for DMA operation.

•BIOS (Basic Input Output System) -: It is a program stored inside a ROM chip. Thisprogram provides the basic hardware information to the Operating Systems.

JUMPERS :-Jumpers are used to configure the motherboard’s different settings. The oldest motherboardcontains various jumpers but latest motherboard contain main two jumpers as following-

1. CMOS CLEAR JUMPER-: This jumper is use to set the BIOS program settings as per default factory setting.

Connectors :-•Connectors provides the connections for other devices to the motherboard. These are the following main connectors on the motherboard -

1.Front Panel Connector.

2.USB Header Connector.

3.Audio Codec Connector.

4.IDE Connector.

5.FDD Connector.

6.Power connector.

7.Additional 4 Pin Connector.

8.CPU Fan Connector.

9.System Case Fan Connector.

1.Front Panel Connector-:It is used to provide the connection for front panel of the system cabinet.

2.USB(Universal Serial Bus) Header Connector-: It provide the connection to the front panel USB port.

3.Audio Codec Connector-: It is use to provide the connection for digital audio sound of the front panel sound ports.

4.IDE (Integrated Device Electronics) Connector-:It is a 40 pin connector that provides the connection for IDE devices such as Hard Disk Drive, CD Drive, DVD Drive etc.

5. FDD Connector-: It is a 34 pin connector, it provide the connection for Floppy Disk Drive (FDD) using a 34 pin cable.

1.Power connector-: There are three types of Power connector used on motherboard.

(a.)AT Power Connector-: It is a 12 pin power connector used on the old motherboards.

(b.)ATX Power Connector-: It is a 20 pin power connector available on ATX motherboards or Integrated motherboards.

(c.)Advance ATX Power Connector-: It is 24 pin power connector available on latest motherboards.

2.Additional 4 Pin Connector-: It is a 4 pin power connector. It provide additional 12 volts to the motherboard.

3.CPU Fan Connector-: It provide the connection to the CPU fan, latest motherboards contain 4 pins CPU fan and old motherboards had 3 pins for CPU fan.

4.System Case Fan Connector-: It provide the connection for additional fan of the cabinet.

Expansion Slots :-•expansion slot is a slot located on the motherboard that allows additional boards to be connected to it. For example, if you wanted to install a new video card install that card into the compatible expansion slot. There are following some of the expansion slots commonly found computers.

1. AGP (Accelerated Graphics Port).

2. AMR (Audio/Modem Riser).

3. CNR (Communication and Network Riser).

4. MCA (Micro Channel Architecture).

5. EISA (Extended Industry Standard Architecture).

6. ISA (Industry Standard Architecture).

7. PCI (Peripheral Component Interconnect).

8. PCI-e (PCI Express).

9. VESA (Video Electronics Standard Association).

AGP (Accelerated Graphics Port) :-•AGP is an advanced port designed for Video cards and 3D accelerators. Designed by Intel,AGP introduces a dedicated point-to-point channel that allows the graphics controller direct access the system memory.

•The AGP channel is 32-bits wide and runs at 66 MHz. This translates into total  bandwidth of 266 MBps, which is much greater than the PCI bandwidth. AGP also supports two optional faster modes, with throughput of 533 MBps and 1.07 GBps.

AMR (Audio/Modem Riser)  :-•AMR is a card that has the functionality of either Modem or Audio or both Audio and Modem on one card. This specification allows for the motherboard to be manufactured at a  lower cost and free up industry standard expansion slots in the system for other additional plug-in peripherals.

CNR (Communication and Network Riser) :-•CNR is a specification that supports audio, modem USB, and Local Area Networking interfaces of core logic chipsets. This technology and the CNR slot was first introduced by Intel February 7, 2000 and was mainly developed by leading hardware and software developers who helped release the AMR (Audio Modem Riser). Today, this slot is no longer found on motherboards.

MCA (Micro Channel Architecture) :-•MCA was introduced by IBM in 1987 as a competitor to the ISA bus. The MCA bus offered several additional features over the ISA such as a 32-bit bus, ran at 10MHz,automatically configure cards (similar to what Plug and Play is today), and bus mastering.The primary downfall of the MCA bus was that it was a proprietary bus and required licensing fees. Because of its proprietary format and competing standards the MCA bus never became widely used and has been fazed out of the desktop computers for greater efficiency.

EISA (Extended Industry Standard Architecture) :-•EISA, It is a bus architecture created by a group of nine computer manufactures in response to MCA bus design by IBM. One big plus point in favor of this architecture is that EISA bus provided 32-bit slots at an 8.33MHz cycle rate for use with 386DX or higher processors. In addition, the EISA also support auto configure and bus mastering feature. 

ISA (Industry Standard Architecture) :-•ISA was originally an 8-bit computer bus that was later expanded to a 16-bit bus. When this bus was originally released it was a proprietary bus, which allowed only IBM to create peripherals and the actual interface. In 1993, Intel and Microsoft introduced a PnP(Plug and Play) ISA bus that allowed the computer to automatically detect and setup computer ISA peripherals, such as a modem or sound card. Using the PnP technology, an end-user would  have the capability of connecting a device and not having to configure the device using jumpers or dip switches.

PCI (Peripheral Component Interconnect) :-•PCI was introduced by Intel. The PCI bus is a 32-bit computer bus that is also available as a 64-bit bus and was the most commonly found and used computer bus in computers during the late 1990's and early 2000's. Today's computers have replace PCI with PCI Express. 

PCI-e (PCI Express) :-•Originally known as 3rd Generation I/O (3GIO), PCI Express, or PCI-e, was approved as a standard on July 2002 and is a computer bus found in computers. PCI Express is designed to replace PCI and AGP and is available in several different formats: x1, x2, x4, x8, x12, x16 and x32.

VESA (Video Electronics Standard Association) :-• VESA is a group of monitor and video card manufacturers that set various display standards. VESA supports and sets industry-wide interface standards for the PC,workstation, and consumer electronics industries.

Input/ Output Ports :-•When referring to a computer or device, a hardware port resembles a plug-in or connection commonly found on the back of a computer. Hardware ports allow computers to have access to external devices such as computer printers.

•There are following mainly used port of the computer

1.AT Port (Old Keyboard Port).

2.Fire wire port.

3.LPT Port (Printer Port).

4.PS/2 Port (Keyboard Port and Mouse Port).

5.Serial Port.

6.Sound In & out and Line out.

7.USB Port.

8.Game Port.

AT Port (Old Keyboard Port) :-•Alternatively referred to as the 101-key keyboard, the AT keyboard is a US standard keyboard introduced in 1986 by IBM. An AT keyboard may also be used to describe a keyboard that uses the AT (Din5) port.

Fire wire port :-•referred to as IEEE-1394, FireWire was developed by Apple in 1995 and is a bus that has a bandwidth of 400-800 Mbps, can handle up to 63 units on the same bus, and is hot swappable. Users more familiar with USB can relate FireWire to USB as it has a lot of the same similarities. Like USB, FireWire has dozens of different devices such as removable drives and cameras.

LPT Port (Printer Port) :-•Short for Line Printer Terminal, LPT is used by IBM compatible computers as an identification for the parallel port such as LPT1, LPT2, or LPT3. This is commonly required when installing a printer on an IBM compatible computer.

PS/2 Port (Keyboard Port and Mouse Port) :-•Often referred to as the mouse port or keyboard port, the PS/2 port was developed by IBM and is used to connect a computer mouse or keyboard to an IBM compatible computer. The PS/2 port is a mini DIN plug that contains six pins and is still found on all IBM compatible computers today, however, is starting to be replaced by USB.

Serial Port :-•An Asynchronous port on the computer used to connect a serial device to the computer and capable of transmitting one bit at a time. Serial ports are typically identified on IBM compatible computers as COM (communications) ports. For example, a mouse might be connected to COM1 and a modem to COM2.

Sound In & out and Line out :-•referred to as audio in and sound in, the line in or line-in is a port found on computer sound cards that enables a user to connect an external audio device such as a cassette tape player,disc player, audio mixer, additional microphones, etc. to record or otherwise manipulate the incoming audio.

                                                       

Game Port :-•The game port is a device port found on IBM PC compatible systems throughout the 1980s and 1990s. It was the traditional connector for joystick input devices until superseded by USB in the 21st century. The game port uses a DA-15 connector and was originally usually mounted on a dedicated ISA card. Since the early 1990s, when the game port moved from dedicated expansion cards to PC I/O or sound cards. 

USB(Universal Serial Bus) Port :-•USB is an external bus standard that supports data transfer rates of 12 Mbps and is capable of supporting up to 127 peripheral devices.

•USB 2.0, also known as hi-speed USB. Hi-speed USB is capable of supporting a transfer rate of up to 480 Mbps and is backwards compatible, meaning it is capable of supporting USB 1.0 and 1.1 devices and cables.

                                                

Motherboard Buses :-•A computer sends several kinds of electronic signals back and forth among its various components. For efficiency, separate paths on the motherboard called buses each carry only one kind of signal. All computers have three fundamental buses:

1.Control Buses.

2.Address Buses.

3.Data Buses.

Control Buses :-•A control bus is a computer bus, used by CPUs for communicating with other devices within the computer. The control bus carries commands from the CPU and returns status signals from the devices, for example if the data is being read or written to the device the appropriate line (read or write) will be active (logic zero).

Address Buses :-•The computer must be able to access every character of memory rapidly, so every character has its own address number. The central processor specifies which addresses it wants to read or write and the address bus carries this information to a memory controller circuit, which locates and fetches the information. Some locations, called random-access memory, hold program instructions and temporary calculation results. Other locations point to the hard drive, mouse and keyboard. The control bus specifies which of these two sets of addresses become active for a particular memory operation.

                                 

Data Bus :-•The data bus acts as a carrier for data from the keyboard, memory and other devices. It passes information at speeds up to billions of characters per second. The central processor reads the data, performs calculations, and moves new data back to memory, the hard drive and other locations. The control bus determines which direction the data is moving. 

                                UNIT-03

Microprocessor :-—Microprocessor is the main processing unit of the computer system. It is also known as CPU (Central Processing Unit). It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and provides results as output. Most of the PC uses microprocessors  design produced by intel and AMD(Advance Micro Devices).

—The 4-bit processors.

—Intel 4004.

—Intel 4040.

—The 8-bit processors.

—8008.

—8080.

—8085.

—The 16-bit processors.

—8086.

—8088.

—80186.

—80188.

—80286.

—32-bit processors: the non-x86 microprocessors

—iAPX 432.

—i960 aka 80960.

—i860 aka 80860.

—Xscale.

—32-bit processors: the 80386 range.

—80386DX.

—80386SX.

—80376.

—80386SL.

—80386EX.

—32-bit processors: the 80486 range.

—80486DX.

—80486SX.

—80486DX2.

—80486SL.

—80486DX4.

—32-bit processors: P5 microarchitecture-

—Original Pentium.

—Pentium with MMX Technology.

—32-bit processors: P6/Pentium M microarchitecture-

—Pentium Pro.

—Pentium II.

—Celeron (Pentium II-based).

—Pentium II Xeon.

—Pentium III.

—Pentium II and III Xeon.

—Celeron (Pentium III Coppermine-based).

—Pentium 4 (not 4EE, 4E, 4F), Itanium, P4-based Xeon, Itanium 2.

—Pentium M.

—Celeron M.

—Intel Core 2 Duo.

—Intel Dual-Core.

—64-bit processors: IA-64.

—64-bit processors: IA-64

—Itanium.

—Itanium 2

—64-bit processors: Intel 64-

—Pentium 4F .

—Pentium D.

—Pentium Extreme Edition.

—Xeon.

—Intel Core 2.

—Core 2 Extreme.

—Core 2 Quad.

—Core 2 Duo.

—Pentium Dual Core.

—Celeron.

—Celeron M.

—Core i3.

—Core i5.

—Core i7.

AMD Microprocessors :-

—Am2900 series (1975).

—29000 (29K) (1987–95).

—29000 (29K) (1987–95).

—x86 architecture processors-

—Am286.

—Am386.

— Am486.

—Am5x86.

—K5 architecture (1995)-

—AMD K5 .

—K6 architecture-

—AMD K6.

—AMD K6-2.

—AMD K6-III.

—AMD K6-2+.

—AMD K6-III+.

—K7 architecture.

—K7 architecture.

—Athlon (Slot A).

—Athlon (Socket A).

—Duron.

—Athlon MP.

—Mobile Athlon 4.

—Athlon XP.

—Mobile Athlon XP.

—Mobile Duron.

—Sempron.

—Mobile Sempron.

—K8 core architecture.

—Opteron.

—Athlon 64 FX.

—Athlon 64.

—Mobile Athlon 64.

—Athlon XP-M.

—Sempron.

—Athlon 64.

—Turion 64.

—Athlon 64 FX.

—Athlon 64.

—Athlon 64 X2.

—Mobile Sempron.

—K10 core architecture

—K10 core architecture.

—Opteron.

—Phenom FX.

—Phenom X4 (9-series).

—Phenom X3 (8-series).

— Athlon 6-seriesl

—Athlon 4-series

—Athlon X2.

—Sempron .

Performance Of Microprocessor :-—The performance of microprocessor depends on various factors as following

1.Clock Speed or Clock Rate.

2.Bus Speed.

3.Bandwidth.

4.Cache Memory.

Clock Speed Or Clock Rate :-—The clock rate typically refers to the frequency at which a CPU is running. It uses the SI unit Hertz. Clock Speed is specified the speed at which the microprocessor process the instructions at a given time. An instruction is a command that the microprocessor execute.The clock rate is only one of several factors that can influence performance when comparing processors in different families.

Bus Speed :-—A system bus is a single computer bus that connects the major components of a computer system. CPU buses can be categorized into two categories.

1.FSB (Front Side Bus).

2.BSB (Back Side Bus).

FSB (Front Side Bus) :-—FSB is a bus that connect CPU to the system’s main memory. It measure the speed at which the CPU communicate with the RAM, north bridge of the motherboard. This bus and the cache connected to it are faster than accessing the system memory (or RAM) via the front-side bus. The speed of the front side bus is often used as an important measure of the performance of a computer.

BSB (Back Side Bus) :-—A back-side bus (BSB), or backside bus, is a computer bus used to connect the CPU to CPU cache memory, usually L2. If a design utilizes it along with a front-side bus(FSB), it is said to use a dual-bus architecture. It is very fast as compared to FSB. 

Bandwidth :-—The Bandwidth specified the number of binary digits that the microprocessor can process in a single instruction. 

Cache Memory :-—The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations. As long as most memory accesses are cached memory locations, the average latency of memory accesses will be closer to the cache latency than to the latency of main memory.

—When the processor needs to read from or write to a location in main memory, it first checks whether a copy of that data is in the cache. If so, the processor immediately reads from or writes to the cache, which is much faster than reading from or writing to main memory.

                                           

Working Of Microprocessor :-—In the microprocessor chip different parts works together to process the data or instructions and provide user valuable information.

—There are some common parts of microprocessor.

1.ALU (Arithmetic Logic Unit).

2.CU (Control Unit).

3.DU (Decode Unit).

4.Instruction Cache.

5.Prefetching Unit.

6.Bus Unit.

7.Data Cache.

8.Registers.

1. ALU (Arithmetic Logic Unit)-: It perform all the arithmetic calculations such as subtraction, addition, division and the logic calculation using the logic gates.

                                     

2.CU (Control Unit)-: It control the flow of data and information to other unit of the microprocessor.

3.Decode Unit-: It decode the various instruction send to the microprocessor. It converts data to a language that is understood by the microprocessor.

4.Instruction Cache-: It store the instructions that are frequently used by the microprocessor to process the data.

5.Prefetching Unit-: This unit controls the flow of data and given instructions to the decode data from the instruction cache. This unit reduced the program execution time.

6.Bus Unit-: It connects the internal units of the microprocessor like the control unit and prefetching unit. The bus unit also connects the microprocessor and external parts of the computer such as RAM and other Input/Output(I/O) devices. This unit is responsible for flow of data, instructions from and to the microprocessor.

                                       

7.Data Cache (L2)-: Data cache store data in the microprocessor and store data that is required by the ALU unit.

8.Registers-: It stores the default information of the microprocessor and store data that is required by ALU. 

                          UNIT-04 

Memory :-—The memory refers to the physical devices used to store programs (sequences of instructions) or data  on a temporary or permanent basis for use in a computer or other digital electronic device. There are following categories of memory.

                                   

Primary Memory :-—Primary storage (or main memory or internal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required.

—Primary Memory is divided in two types -

1.RAM (Random Access Memory).

2.ROM (Read Only Memory).

RAM (Random Access Memory) :-—Random access memory (RAM) is the best known form of computer memory. RAM is considered "random access" because you can access any memory cell directly if you know the row and column that intersect at that cell. It is also known as volatile memory.

—RAM is categorized in two categories -

1.DRAM.

2.SRAM.

DRAM (Dynamic Random Access Memory) :-—Dynamic random-access memory (DRAM) is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit,conventionally called 0 and 1. Since capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory.

—The advantage of DRAM is its structural simplicity: only one transistor and a capacitor arerequired per bit, compared to four or six transistors in SRAM. This allows DRAM to reach very high densities. Unlike flash memory, DRAM is volatile memory, since it loses its data quickly when power is removed.

—The transistors and capacitors used are extremely small; billions of transistors and capacitors can fit on a single memory chip.

FPM(Fast Page Mode)-DRAM :- —It is a standard DRAM exist through a technique called paging. This method was popularon 32 bit wide memory system on “80486” processors. But failed in favor of Pentium because of there 64 bit wide memory.

EDO(Extended Data Out)-DRAM :-—Sometimes referred to as Hyper Page Mode enabled DRAM, is similar to Fast Page Mode DRAM with the additional feature that a new access cycle can be started while keeping the data output of the previous cycle active. It was 5% faster than FPM DRAM, which it began to replace in 1995, when Intel introduced the 430FX chipset that supported EDO DRAM.

SD(Synchronous Dynamic)-RAM :-— SDRAM has a synchronous interface, meaning that it waits for a clock signal before responding to control inputs and is therefore synchronized with the computer's system bus.SDRAM is widely used in computers; from the original SDRAM, further generations of DDR (or DDR1) and then DDR2 and DDR3 have entered the mass market, and QDR also used. DDR4 currently being designed and anticipated to be available in 2013.

DDR(Double Data Rate)-SDRAM :-—Compared to single data rate SDRAM, the DDR SDRAM interface makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals.The name "double data rate" refers to the fact that a DDR SDRAM with a certain clock frequency achieves nearly twice the bandwidth of a SDR SDRAM running at the same clock frequency, due to this double pumping.

—With data being transferred 64 bits at a time, DDR SDRAM gives a transfer rate of(memory bus clock rate) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number ofbits/byte). Thus, with a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s.

DDR2-SDRAM :-

—In addition to double pumping the data bus as in DDR SDRAM. DDR2 allows higher bus speed and requires lower power by running the internal clock at half the speed of the data bus. The two factors combine to require a total of four data transfers per internal clock cycle. With data being transferred 64 bits at a time, DDR2 SDRAM gives a transfer rate of (memory clock rate) × 2 (for bus clock multiplier) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz,DDR2 SDRAM gives a maximum transfer rate of 3200 MB/s.

DDR3-SDRAM :-—The primary benefit of DDR3 SDRAM over its immediate predecessor, DDR2 SDRAM, is its ability to transfer data at twice the rate. With two transfers per cycle of a quadrupled clock signal, a 64-bit wide DDR3 module may achieve a transfer rate of up to 64 times the memory clock speed in megabytes per second (MB/s). With data being transferred 64 bits at a time per memory module, DDR3 SDRAM gives a transfer rate of (memory clock rate) × 4(for bus clock multiplier) × 2 (for data rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus with a memory clock frequency of 100 MHz, DDR3 SDRAM gives a maximum transfer rate of 6400 MB/s.

R-DRAM:-—RDRAM was initially expected to become the standard in PC memory, especially after Intel agreed to license the Rambus technology for use with its future chipsets. Further,RDRAM was expected to become a standard for VRAM. However, RDRAM got embroiled in a standards war with an alternative technology - DDR SDRAM, quickly losing out on grounds of price, and, later on, performance.

SG-RAM :-—SGRAM is a specialized form of SDRAM for graphics adaptors. It adds functions such as bit masking (writing to a specified bit plane without affecting the others) and block write (filling a block of memory with a single colour). Unlike VRAM and WRAM, SGRAM is single-ported. However, it can open two memory pages at once, which simulates the dual port nature of other VRAM technologies.

V-RAM :-—VRAM is a dual-ported variant of DRAM that was once commonly used to store the frame-buffer in some graphics adaptors. VRAM has two sets of data output pins, and thus two ports that can be used simultaneously. The first port, the DRAM port, is accessed by the host computer in a manner very similar to traditional DRAM. The second port, the video port, is typically read-only and is dedicated to providing a high throughput.

ROM :-—Read-only memory (ROM), also known as firmware, is an integrated circuit programmed with specific data when it is manufactured. ROM chips are used not only in computers, but in most other electronic items as well. ­ ROM Types.

—There are five basic ROM types:-

1.Mask ROM.

2.PROM.

3.EPROM.

4.EEPROM.

5.Flash memory.

Mask ROM :-—Mask ROM is a type of ROM whose contents are programmed by the manufacturer.

—The main advantage of mask ROM is its cost. Per bit, mask ROM is more compact than any other kind of semiconductor memory. Since the cost of an integrated circuit strongly depends on its size, mask ROM is significantly cheaper than any other kind of semiconductor memory.

—Some integrated circuits contain only mask ROM. Other integrated circuits contain mask ROM as well as a variety of other devices. In particular, many microprocessors have mask ROM to store their microcode. Some microcontrollers have mask ROM to store the bootloader or all of their firmware.

P-ROM :-—At the time of manufacturing the chip is made as a blank chip and using a specific P-ROM writer the information is stored into the chip. 

—These types of memories are frequently seen in video game consoles, mobile phones,radio-frequency identification (RFID) tags, implantable medical devices, high-definition multimedia interfaces (HDMI) and in many other consumer and automotive electronics products.

EP-ROM :-—It is a P-ROM with an option to erase its contains, if user wants to change the information stored into it. The program can be erased using a special glass window in the middle of the chip. This window allow ultra violet light that can be shined on the EP-Rom to erase it’s contains. After erasing the EP-ROM it can be reprogramed using the Rom writer. 

EEP-ROM :-—It another type of EP-ROM, the difference between EPROM and EEP-ROM is the way to erase the contains. In EP-ROM the contains are erased by using the ultraviolet rays, whereas in the EEP-ROM the contains are erased by using high voltage electricity (more than +5 volts).

Flash ROM :-—Flash memory was developed from EEPROM. It can be erased or reprogramed using the normal operating voltages. Example of flash ROM is Pen Drive, memory cards.  

MEMORY PACKAGING 

Memory Modules :-—Memory packages are small circuits that contain memory chips or modular. It is also known as memory modular. The memory modules are  available in following packaging.

1.Dual in-line Package (DIP).

2.Single In-line Pin Package (SIPP).

3.Single In-line Memory Module (SIMM).

4.Dual In-line Memory Module (DIMM).

5.Rambus In-line Memory Module (RIMM).

6.Small outline DIMM (SO-DIMM).

7.Small outline RIMM (SO-RIMM).

Dual in-line Package (DIP):-—DIP is an electronic device package with a rectangular housing and two parallel rows of electrical connecting pins. It was introduced with the first PC that could store only 16 KB of information each. Later with AT machines 256 KB of modules were introduced. pre-fast page mode DRAM (FPRAM) use this module.

Single In-line Pin Package (SIPP) :-—It consisted of a small printed circuit board upon which were mounted a number of memory chips. It had 30 pins. This type of memory was used in 80286 and some 80386 systems. It was later replaced by SIMMs, which proved to be easier to install. It uses FPRAM and EDO-DRAM.

Single In-line Memory Module (SIMM):-—The SIPP's 30 pins often bent or broke during installation, which is why they were quickly replaced by SIMMs which used contact plates rather than pins. It was use by EDO-DRAM.

—The first version of SIMMs has 30 pins and provides 8 bits of data .

—The second version of SIMMs has 72 pins and provides 32 bits of data. 72-pin SIMMs had replaced 30-pin SIMMs in new-build computers, and were starting to themselves be replaced by DIMMs.

Dual In-line Memory Module (DIMM):-—These modules are mounted on a printed circuit board and designed for use in personal computers, workstations and servers. The main difference between SIMMs and DIMMs is that DIMMs have separate electrical contacts on each side of the module, while the contacts on SIMMs on both sides are redundant. Another difference is that standard SIMMs have a 32-bit data path, while standard DIMMs have a 64-bit data path.

—The most common types of DIMMs are:

1.100-pin DIMM, used for printer SDRAM.

2.168-pin DIMM, used for SDRAM.

3.184-pin DIMM, used for DDR SDRAM.

4.240-pin DIMM, used for DDR2 SDRAM, DDR3 SDRAM and FB-DIMM DRAM.

Rambus In-line Memory Module (RIMM) :-—When Intel introduced P-4 microprocessor, there was a requirement of very fast memory for it and their choice was “RDRAM”. The RDRAM uses a special 184 pins RIMM memory module. It was available on intel 850 series chipset, but RIMM was no so popular because of its cost. RIMM is very costly memory module. It consist two notches closer to each other then DIMM module.

Small outline DIMM (SO-DIMM) :-—SO-DIMMs are a smaller alternative to a DIMM, being roughly half the size of regular DIMMs. SO-DIMMs are often used in systems which have space restrictions such as notebooks, small footprint PCs, high-end upgradable office printers, and networking hardware like routers.

—The most common types of DIMMs are:

1.100-pin SO-DIMMs have two notches,

2.144-pin SO-DIMMs have a single notch near (but not at) the center, and

3.200-pin SO-DIMMs have a single notch nearer to one side.

4.204-pin SO-DIMMs (DDR3) have a single notch closer to the center than on 200-pin SO

DIMMs.

Small outline RIMM (SO-RIMM):-—Small outline RIMM (SO-RIMM). Smaller version of the RIMM, used in laptops.Technically SO-DIMMs but called SO-RIMMs due to their proprietary slot. This module uses RDRAM for portable device. 

UNIT-05

Hard Disk Drive :-—A hard disk drive (HDD) is a data storage device used for storing and retrieving digital information using rapidly rotating discs (platters) coated with magnetic material. It is a permanent storage device . Data is read in a random-access manner. An HDD consists of one or more rigid ("hard") rapidly rotating discs (platters) with magnetic heads arranged on a moving actuator arm to read and write data to the surfaces.

Components Of Hard Disk Drive :-

—A HDD(Hard Disk Drive) consist the following main components.

1.Platters or Recording Media.

2.Read-write heads.

3.Spindle motor.

4.Head Actuator .

5.Air Filters.

6.Logic Board.

7.Power Connector.

8.Jumper Block..

9.Data Cable Connector.

Platters or Recording Media :-—A hard disk drive platter is the circular disk on which magnetic data is stored in a hard disk drive. Hard drives typically have several platters which are mounted on the same spindle. A platter can store information on both sides, requiring two heads per platter.

—The platters are made from a non-magnetic material, usually aluminum alloy, glass, or ceramic, and are coated with a layer of magnetic material typically 10–20 nm in depth, with an outer layer of carbon for protection. 

Read-write heads :-—Read-write heads move above the disk platter and transform the platter's magnetic field into electrical current (read the disk) or vice versa – transform electrical current into magnetic field (write the disk).

—In modern drives there is one head for each magnetic platter surface on the spindle,mounted on a common arm. 

Spindle motor :-—A typical HDD design consists of a spindle that holds Platters. It runs the platters at speeds varying from 4,200 rpm in energy-efficient portable devices, to 15,000 rpm for high performance servers. The first HDDs spun at 1,200 rpm and, for many years, 3,600 rpm was the normal. Today, most consumer HDDs operate at a speed of 7,200 rpm.

                                      

Head Actuator  :-—An actuator is a type of motor for moving or controlling a mechanism or system. In the hard disk drive actuator is a permanent magnet and moving coil motor that swings the heads to the desired position. 

Air Filters:-

—Air filters helps to remove internal air inside the hard disk drive during the platters

rotation. These filters also protect the HDD from outside air & dust.

                                               

Logic Board:-—It is main control circuit board of the HDD that control and connect several parts of the HDD and also provide the power supply to the different motors and components.

                                     

Power Connector :-It is use to connect the power cable from the power supply(SMPS) to the HDD.

                                     

Jumper Block :-—This part of the HDD have some pins for jumper setting of the HDD. Jumpers are use to make the HDD master or slave, in modern HDD it is use to control the speed of HDD.

  

Data Cable Connector:-It is also a connector of HDD that is use to connect the data cable of the HDD from the motherboard.

                                           Hard Disk Drive Interfacing

HDD Interfacing :-—Interfacing means connecting a device to another device. This interfacing can be hardware or software. There are following hardware interfacing of HDD.

—IDE (Integrated Device Electronics) or EIDE.

—SATA (Serial Advance Technology Attachment ).

—USB (Universal Serial Bus).

—SCSI (Small Computer System Interface).

—SAS (Serial Attached-SCSI).

—(FC) Fibre Channel.

USB (Universal Serial Bus) :-—External removable HDDs typically connect via USB. Plug and play drive functionality offers system compatibility, and features large storage options and portable design. External HDDs are available in 2.5" and 3.5" sizes. Common storage sizes are 160GB, 250GB, 320GB, 500GB, 640GB, 750GB, 1TB, and 2TB.

—External hard drives generally have a slower transfer rate then that of an internally mounted hard drive connecting through SATA.

DE (Integrated Device Electronics) or EIDE :-—The 40-pin IDE/ATA connection transfers 16 bits of data at a time on the data cable. The data cable was originally 40-conductor.

—EIDE was an unofficial update to the original IDE standard, with the key improvement being the use of direct memory access (DMA) to transfer data between the disk and the computer without the involvement of the CPU.

SATA (Serial Advance Technology Attachment ) :-— Serial ATA was designed to replace the older IDE (known as ATA or PATA). It offers several advantages over the older interface: reduced cable size and cost (seven conductors instead of 40), native hot swapping, faster data transfer through higher signaling rates.

—The SATA data cable has one data pair for transmission of data to the device, and one pair for receiving from the device.

SCSI (Small Computer System Interface) :-—SCSI originally named SASI (Shugart  Associates System Interface) was standard on servers, workstations, Commodore Amiga, and Apple Macintosh computers.

—This interface is more faster then ATA and it also allow more HDD then ATA and SATA to connect with the single PC.

SCSI (Small Computer System Interface) :-

SAS (Serial Attached-SCSI) :-—The SAS is a new generation serial communication protocol for devices designed to allow for much higher speed data transfers and is compatible with SATA. SAS uses a mechanically identical data and power connector to standard 3.5-inch SATA1/SATA2 HDDs, and many server-oriented SAS RAID controllers are also capable of addressing SATA HDDs. SAS uses serial communication instead of the parallel method found in traditional SCSI devices but still uses SCSI commands.

(FC) Fibre Channel :-—It is a successor to parallel SCSI interface on enterprise market. It is a serial protocol. Recently other protocols for this field, like iSCSI and ATA over Ethernet have been developed as well.

                                                  Disk Geometry

Disk Geometry :-—The HDD store data as magnetic information on it’s surface. If the data is store continuously one next to another than at the time of retrieve of data, the disk will have to scan entire surface to find the required information.

—To arrange the data on the disk surface. The disk surface is divided into different sections as following.

1.Sides or Head.

2.Track.

3.Sectors.

 4.Cylinders.

Sides or Head :-—The HDD contain multiple platters or disks. Each side of disk will have a separate read/write head to read and write the information on that side. All heads are connected to a single head rack which makes these read/write heads to move together over different parts of the disk drive. Each head is specified by the head number such as head0, head1, head2 and so on.

Track :-—Each side of HDD platter surface is divided into concentric circles that’s are called track. These tracks are not visual marks on the disk surface, instead these are magnetic information written during the low level formatting of HDD.

      

                                      

Sectors :-—The track is very big area to store the data, so that  tracks are divided into number of sectors. Like a track sectors are not visual on the disk surface. It is also written information during the low level formatting. Almost all drives stores minimum of 5kb of data per sector.

              

Cylinders :-—On a HDD which have more than one side of the platter same track of different platters form a imagine cylinder like structure when data is stored on the HDD. It is written cylinder by cylinder. A track usually refers to one part of the cylinder. A cylinder is combination of all the tracks having same value. 

            

                                  UNIT-06

Floppy Disk Drive :-—A floppy disk is a disk storage medium. Floppy disks, initially as 8-inch (200 mm) media and later in 5.25-inch (133 mm) and 3.5-inch (90 mm).

—While floppy disk drives still have some limited uses, especially with legacy industrial computer equipment.

—Now a days most common floppy disk is 1.44 MB storage capacity with 3.5 inch size.

Components of Floppy Disk Drive :-—There are following components of FDD (Floppy disk Drive)-

1.Read/Write Head.

2.Head Actuator.

3.Stepper Motor.

4.Spindle Motor.

5.Logic Board.

6.Data Cable Connector.

7.Power Cable Connector.

8.Face-plate.

Floppy Disk Construction:-—Both the 5.25 inch and the 3.5 inch floppy disks have some common parts and construction as following.

1.Jacket (available in both 3.5``and 5.25`` ).

2.Recording Media (available in both 3.5``and 5.25``).

3.Label Area (available in both 3.5``and 5.25``).

4.Drive Hub Hole (5.25``).

5.Index Hole (5.25``).

6.Alignment Hole (3.5``).

7.Read/Write Window (available in both 3.5``and 5.25``).

8.Write Enable Notch (5.25``).

9.Protection Shutter (3.5``).

10.Spindle Connector (3.5``).

11.High Density Detection hole (3.5``).

12.Stress Relief Notch (available in both 3.5``and 5.25``).

FDD Interfacing :-—To connect a FDD to the computer, there is  a standard interface called SA-450. This interface was used for 5.25`` FDD.

—The connector for 3.5`` floppy disk drive is a 34 pins FDD connector.

 UNIT-07 

Optical Disk Drive :-—In computing, an optical disc drive (ODD) is a disk drive that uses laser light or electromagnetic waves to read/write the data. Some drives can only read from discs, but recent drives are commonly both readers and recorders, also called burners or writers. Compact discs(CD), DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives.

CD-ROM Drive :-—CD-ROM Drive can only read information from the compact disk. A CD-ROM disk is a very high capacity storage floppy disk which can store about 700 MB of data. A CD-ROM disk mainly used to store permanent information that does not required any changes. The software, movies, audio and video songs  are distributed on the CD-ROM disks.

CD-R/W Drives :-—CD-R/W stands for compact disk read and write. It is a drive that can read the optical information from CD-ROM disk and also write(burn) the information on to the CD-R disks.

   WORKING OF  CD-ROM DRIVE

—CD-ROM disks are mirror like disk. The data from the disk retrieve using laser beam.

—When the CD-ROM is placed on the tray and tray closed, the CD-ROM drive starts rotating the disk. A laser beam optical assembly moves in and out over the disk. The optical lens starts reading the information stored on the disk surface using a laser beam. This laser light is focused on the CD surface by a focusing coil of optical assembly. This laser beam strike the disk surface area.

—Data is store on the CD in the form of flat area(land) and small depression(pits). These land and pits used to store binary 1 & 0. The optical light when fall on the “land” area it reflected directly back to the optical assembly. When light fall on the “pit” area it does not receive back to the optical assembly.

—When the light receives by the optical assembly by a light sensing diode and this diode generate an “1” electrical signal to the logic board and un-received light sends a “0” signal to the logic board.

DVD Drive :-—It is faster and can hold more data then the CD disk. There are different variations of DVD such as DVD-ROM, DVD-R, DVD video and DVD Audio. 

Types of DVD based on sizes :-—There are following different types of DVDs on the basis of size.

1.DVD-5.

2.DVD-9.

3.DVD-10.

4.DVD-18.

—DVD-5-: It is a single sided single layered disk which can store maximum “4.7 GB” of data.

—DVD-9-: It is a single sided double layered disk. It can store maximum “8.5 GB” of data.

—DVD-10-: It is a double sided single layered disk. It can store maximum “9.4 GB” of data.

—DVD-18-: It is a double sided double layered disk. It can store maximum “17 GB” of data.

Types of DVD based on uses :-—There are following different types of DVDs on the basis of uses.

1.DVD-ROM.

2.DVD-VIDEO.

3.DVD AUDIO.

4.DVD-R & DVD+R.

5.DVD-RW & DVD+RW.

6.DVD RAM.

7.DVD-VR & DVD+VR.

8.HD DVD.

—DVD-ROM-: It stores data ranging from 4.7 GB to 17 GB. A DVD-ROM disk mainly used to store permanent information that does not required any changes. The software, movies, audio and video songs  are distributed on the DVD-ROM disks.

 DVD-VIDEO :-—DVD-Video is a video format used to store digital video on DVD discs. Discs using the DVD-Video specification require a DVD drive and an H.262/MPEG-2 Part 2 decoder (e.g., a DVD player, or a computer DVD drive with a software DVD player). Commercial DVD movies are encoded using a combination of H.262/MPEG-2 Part 2 compressed video and audio of varying formats. Typically, the data rate for DVD movies ranges from 3 Mbit/s to 9.5 Mbit/s, and the bit rate is usually adaptive. It was first available for retail around 1997.

DVD AUDIO :-—DVD-Audio (commonly known as DVD-A) is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio is not intended to be a video delivery format and is not the same as video DVDs containing concert films or music videos.

—The first discs entered the marketplace in 2000. DVD-Audio was in a format “war” with Super Audio CD (SACD).

DVD-R & DVD+R :-—DVD-R is a DVD recordable format. A DVD-R typically has a storage capacity of 4.9 GB. Pioneer has also developed an 8.5 GB dual layer version, of  DVD-R DL, also available in market from 2005. Data on a DVD-R cannot be changed.

—A DVD+R is a recordable optical disc. It is similar to, but incompatible with, the older DVD-R standard.

—DVD+R discs must be formatted before being recorded by a compatible DVD video recorder. DVD-R do not have to be formatted before being recorded by a compatible DVD video recorder.

DVD-RW & DVD+RW :-—A DVD-RW disc is a rewritable optical disc with equal storage capacity to a DVD-R, typically 4.7 GB. The primary advantage of DVD-RW over DVD-R is the ability to erase and rewrite to a DVD-RW disc.

— DVD+RW supports a method of writing called "lossless linking", which makes it suitable for random access and improves compatibility with DVD players. DVD+RW must be formatted before recording by a DVD recorder.

DVD RAM :-—DVD-RAM (DVD–Random Access Memory) is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD writers. DVD-RAM technology provides excellent data integrity, data retention and damage protection through a number of mechanisms and properties.

—DVD-RAM (DVD–Random Access Memory) is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD writers. DVD-RAM technology provides excellent data integrity, data retention and damage protection through a number of mechanisms and properties.

—DVD-RAM (DVD–Random Access Memory) is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD writers. DVD-RAM technology provides excellent data integrity, data retention and damage protection through a number of mechanisms and properties.

DVD-VR & DVD+VR :-—The DVD-VR standard defines a logical format for video recording on DVD-R, DVD-RW, and DVD-RAM style media, including the dual layer versions of these media. As opposed to media recorded with the DVD+VR recording standard, the resulting media are not DVD-Video compliant, and do not play back in some DVD-Video players. Most DVD video recorders in the market that support DVD-R, DVD-RW, or DVD-RAM media record to these media in DVD-VR mode, as well as in a DVD-Video compliant mode. It is possible to use the DVD-VR format with DVD+R and DVD+RW media, but no examples are known other than some PC based recording utilities.

HD DVD:-—HD DVD (short for High Definition/Density Digital Versatile/Video Disc) is a discontinued high-density optical disc format for storing data and high-definition video.  Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format.

—Capacity15 GB (single layer)30 GB (dual layer).

Blu-ray Disc :-—Blu-ray or Blu-ray Disc (BD, BRD) is a digital optical disc data storage format. It was designed to supersede the DVD format, in that it is capable of storing high-definition video resolution (1080p). Blu-ray Discs contain 25 GB per layer, with dual layer discs (50 GB) Triple layer discs (100 GB) and quadruple layers (128 GB) are available for BD-XL re-writer drives.  The name "Blu-ray" refers to the blue laser (specifically, a violet laser) used to read the disc. The main application of Blu-ray is as a medium for video material such as feature films and physical distribution of video games for the PlayStation 3,PlayStation 4 and Xbox One. Besides the hardware specifications, Blu-ray is associated with a set of multimedia formats. 

  UNIT-08

SMPS (Switch Mode Power Supply) :-—Power supply is an electrical device that provide power to the electronic devises of the computer system. This device is responsible for power conversion from high volt AC into compatible DC voltages. Now a days power supplies are available in range from 450 watt to 600 watt.

—Different components of the system required different voltages to operate. Various voltages provided by the power supply are as following.

1. -12 volts-: Required by some serial ports and other serial port compatible hardware.

2. -5 volts-: Required by older floppy controller and ISA bus cards. It is provided for some older hardware of the system

3. 0 volts-: It is ground (GND) voltages, also known as earth.

4. +3.3 volts-: Required by processor’s socket or slot, DIMM, PCI, AGP cards. This voltage was introduce in ATX SMPS.

5. +5 volts-: Required by the motors in the system such as cooling fans and disk drive spindle and stepper motors. It is also required by system bus slots.

6. +12 volts-: Required by disk drive logic card, ISA cards, SIMM and other miscellaneous components of the system.  

Power Supply Control Signals :-—Older SMPS uses mechanical switches for turn on and off the computer system, but the new power supply operated using different control signals. These control signals are as following-:

1.Power Good Signal

2.Power (PS-ON)

3.Voltage Stand By (VBS) 

Power Good Signal :-—It indicate to the microprocessor that all the supplies given are at proper level. It also inform to the microprocessor that power supply is working properly and prevents computer from operating on improper voltage level.

Power (PS-ON):-—Controls the power supply and it is a part of ATX standard. It caries a low voltage logic level signal from the motherboard to power supply that indicates it when to turn off and on.

Voltage Stand By (VBS):-—It supplies power to the line that is used to “Power Stand By” circuitry. It is always on when the AC power input is active even if the system is off.

TYPES OF POWER SUPPLY :-—Power supply is a system which provides power to the circuits or the devices connected to it. Power supply also convert AC voltage into DC voltage. There are basically two types of power supply.

1.Linear Power Supply

2.Switch Mode Power Supply (SMPS).

Linear Power Supply :-—It transfer incoming high voltage through step down transformer to decrease the voltage. A rectifier circuit is used to rectify AC voltage to pulsating DC voltage. The capacitor filters are used  to filter the received DC voltage from the rectifier.

 Switch Mode Power Supply (SMPS) :-—It uses high switching frequency. It is compact and can deliver very high power. It is also used as AC to DC converter. It also consist linear power supply. In SMPS incoming power is passed through a network of transistor and transformers. This network switches its state on and off number of times per second. The SMPS has the following types for computer system.

1.AT SMPS.

2.ATX SMPS.

3.BTX SMPS.

AT SMPS :-—This type of SMPS is the oldest technology. It was used with PC/AT system it consist the following main connectors in of output-

1.Motherboard Power Connector-: It is a set of two 6 pin connectors.

                                        

2. Molex connector-:It is a 4 pins connectors which provides 5volts, 12 volts, and grounds. This connector provides the power to the Hard Disk Drive, CD/DVD Drive and 5.25 inch Floppy Disk Drive.

3.Berge Connector-: This connector provides the power supply same as Molex connector, but it is smaller than Molex connector. It provide the power to the 3.5 inch Floppy Disk Drive.

 ATX SMPS:-—ATX stands for Advanced Technology extended. It is used with latest ATX motherboard. This power supply is available in two different versions 20 pin ATX and 24 pin ATX which is also known as BTX. It is used in Pentium-III, Pentium-IV and AMD CPUs. It has the following additional connectors than AT SMPS.

01.20 Pin ATX Power.

02.20+4 Pin ATX Power.

03.AMP ATX 12v Power Connector.

04.Serial ATA Power Connector.

05.Berg Floppy Power Connector.

20 Pin ATX Power :-—The 20-pin Main power connector is standard for all power supplies conforming to the ATX and ATX12V 1.x form factors, and consists of a Molex Mini-Fit, Jr. connector housing with female terminals.

                   

20+4 Pin ATX Power  :-—The 20 +4 may be used for either 20 pin connector motherboards or 24 pin connector motherboards.

                    

AMP ATX 12v Power Connector :-—4 pin connector for the Intel Pentium 4 CPU. This connector provide additional 12 volts power to the motherboard.

                                      

Serial ATA Power Connector :- —This connector is use to provide power supply to the SATA type of HDD and CD/DVD Drives.

 

UNIT-09 

BIOS :-—The BIOS (Basic Input/Output System) software is built into the PC, and is the first software run by a PC when powered on. The fundamental purposes of the BIOS are to initialize and test the system hardware components, and to load an operating system or other program from a mass memory device.

—The BIOS provides a consistent way for application programs and operating systems to interact with the keyboard, display, and other input/output devices.

Functions of BIOS :-—In most PCs, the BIOS has 4 main functions as mentioned below.

1.POST - Test the computer hardware and make no errors exist before loading the operating system. Additional information on the POST can be found on our POST and Beep Codes page.

2.Bootstrap Loader - Locate the operating system. If a capable operating system is located, the BIOS will pass control to it.

3.BIOS drivers - Low level drivers that give the computer basic operational control over your computer's hardware.

4.BIOS or CMOS Setup - Configuration program that allows you to configure hardware settings including system settings such as computer passwords, time, and date.

 UNIT-10 

TROUBLESHOOTING :-

—Problem No. 01-: The system is not powered ON.

—Reason-:

1.There is no power supply in the main power board.

2.Power cable may be faulty.

3.SMPS may not working proper.

4.Power button is not working proper or not connected to the motherboard proper.

5.BIOS jumper may be not in normal position.

6.Power connector of SMPS is not connected proper with the motherboard.

7.BIOS setting may be wrong.

8.Motherboard may be faulty.

—Solution-:

1.Test the power board and power cable through tester, multi-meter or by connecting other electronic device like monitor.

2.Test the SMPS by  shorting green and black wire.

3.Try to power ON by shorting the power pins of Front-Panel connecter by a metal.

4.Check the BIOS jumper is connected in 1and2 pins or connected in 2and3 pins. It should be in 1and2.

5.If BIOS setting is wrong first default the bios by removing battery or by the jumper, then again power ON by setting the jumper in normal.

—Problem No. 2-: There is no display in the system.

— Reason-:

1.12 volt additional power connector is not connected.

2.RAM is not connected proper or RAM may be faulty.

3.BIOS jumper may be not in normal position.

4.CPU may not connected proper.

5.BIOS chip may be faulty.

6.Motherboard may be faulty.

—Solution-:

1.Check the 12 volt additional power connector.

2.Check the RAM is proper connected or not connected. Now remove the RAM and power ON the system if there is any type of beep it means BIOS and CPU is working proper, RAM may be faulty.

3.Remove the CPU and check all pins are in good condition and connect again.

4.Check the BIOS jumper is connected in 1and2 pins or connected in 2and3 pins. It should be in 1and2.

5.Test BIOS chip through the diagnostic card.

6.Test Motherboard through the diagnostic card.

—Problem No. 3-: System is shutting down or restart after few seconds.

—Reason-:

1.SMPS is not providing proper voltage.

2.CPU fan is not connected proper.

3.Silicon paste have removed, not  enough.

4.Power button is in pressed  position.

—Problem No. 4-: System is shutting down or restart after some time.

— Reason-:

1.There is heating Problem in the system.

2. SMPS is not providing the proper power supply.

3.Operating System (O.S.) may be corrupted.

4.There may be virus in the system

— Solution-:

1.Check the CPU fan & SMPS fan is it working proper, and there may be dust in the system.

2.Check the output voltages of SMPS through multi-meter.

3.If system is restart during the booting time, so OS is corrupted. Reinstall or repair it.

4.Try the system to run in BIOS up to that time if it is not have problem then OS is corrupted or have virus.

—Problem No 5-: System is hanging during the booting process.

—Reason-:

1.HDD or CD/DVD  data cable may be faulty.

2.CPU heating.

3.BIOS chip may be faulty.

4.RAM may be faulty.

—Solution-:

1.Remove the data cable from the system and try again to power ON the system.

2.Check the CPU fan is it working proper, and there may be dust in the system.

3.Test the BIOS chip using diagnostic card.

4.Check the RAM, is there any type of moister in the RAM.

—Problem No 6-: System is hanging. Or system is working slow down.

—Reason-:

1.There may be heating problem in the system.

2.There may be virus in the system.

3.There may be too much temp and cookies in the system.

4.The may be more fragmented files in the system.

5.RAM is not working proper.

6.HDD data cable may be faulty.

—Solution-:

1.Check the system, SMPS and CPU fan is it working proper, and there may be dust in the system.

2.Run the anti-virus in the system.

3.Run the Disk cleanup in the system.

4.Run the Disk defragment in the system.

5.Check the RAM, is there any type of moister in the RAM.

6.Change the Data cable from the system and try again to power ON the system.

—Problem No 7-: fatal error during running the OS or installing the OS.

—Reason-:

1.HDD data cable may be faulty.

2.RAM may be faulty.

3.HDD may be faulty.

—Solution-:

1.Change the Data cable from the system and try again to power ON the system.

2.Check the RAM, is there any type of moister in the RAM.

3.Change the HDD and try to install the OS.

                                    UNIT-11

                          -: PRINTERS :-

Printer :-*In computing, a printer is a output device which produces a representation of an electronic document on physical media such as paper or film. Many printers are local peripherals connected directly to a nearby personal computer. Individual printers are often designed to support both local and network connected users at the same time. 

*Printers are categorized based on the mechanism used by the printer to print the image and they can also be categorized based on the image creation method used by them.

Types of Printer :-*Based on the image creation method:

1.Fully Formed character printer.

2.Bit Image Printer

*Based on Printing Mechanism

1.Impact Printer.

2.Non-Impact Printer.

Fully Formed character printer :-*Type-writer is very good example of fully formed character printer. In a type-writer the alphabet shapes are made in advance and provide in the type-writer itself. By pressing any key one can get the shape.

*Just like the type-writer these printers contains all the printable characters in the printer as part of printer hardware itself.

*One major drawback of these printer is one can’t use to print a character not provided within the printer. There are some fully formed character printers are-

1.Daisy wheel printer.

2.Daisy chain printer.

3.Drum printer.

*Bit Image Printer :-*In this method printer does not contain any specific character shape , instead it prints the required character using a matrix of dots. These dots are arranged to re-assemble the character and shape that you want to print. These printers can be used to print text as well as graphic image. There are some bit image printers as following-

1.Dot-Matrix Printer.

2.Inkjet Printer.

3.Laser Printer.

*Impact Printer :-*These printers uses impact to create an image on the output media.

*Advantage of the impact printer is that they can be used to print multiple copies of a print using the carbon paper. Disadvantage of impact printer is they produce too much noise during operation. Some common impact printers are-

1.Dot-Matrix Printer.

2.Daisy wheel printer.

3.Daisy chain printer.

4.Drum printer.

*In this category Dot-matrix printer is most common used printer. A Dot-matrix printer is an impact printer which works on bit image technology.

*Non-Impact Printer:-*Non-Impact printer do not strike any ribbon or paper to produce the image, instead they use an spring, electro-static magnetization or heat process to produce the required image. Soundless operation and very high quality output of these printers are making them very popular.

*Disadvantage with these printers is they cannot be used to print carbon copies or multiple copies in a single pass. Some common non-impact type of printers are-

1.Inkjet/Deskjet Printer.

2.Thermal Printer.

3.LaserJet Printer.

*Dot-Matrix Printer :-*Dot matrix printing or impact matrix printing is a type of computer printing which uses a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like the print mechanism on a typewriter. However, unlike a typewriter or daisy wheel printer, letters are drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be produced. The speed of these printers measured in CPS (Character Per Second). Printing speed range from 100 CPS to 1200 CPS.

Working of Dot-Matrix Printer :-*The main image formation part of a dot-matrix printer is the “print head”. Print head is available in  9 pins to 18, or 24 pins. A print pin mechanism is a combination of permanent magnet, electro-magnet, spring and print pin.

*There are different steps of printing process as following-

1.The computer sends  a series of ASCII(American Standard Code for Information Interchange) codes that represent characters

2.ASCII codes receive by the printer are stored inside a buffer(memory).

3.Based on the received ASCII codes the processor inside the printer selects a particular dot pattern from the bit map table.

4.The printer processor sends signals to the print head and print head starts firing the pins.

5.To fire the pins the electro-magnet is energized. It repels the magnet connected at the end of the pin so the pin moves.

6.The moving pin strikes a ribbon that makes a inked dot over the paper,

7.After the pin firing the electromagnetic is de-energized and spring pull back into its original position.

Working of Dot-Matrix Printer :-

Inkjet Printer :-*Inkjet printers are bit image, non-impact type of printers. These printers produce character shape and image by spraying from tiny nozzle on to the paper. These printers are light weight and small size. The speed of these printers measured in PPM (Page Per Minute). The printing speed range from 5 PPM to 15 PPM.

*The biggest difference between inkjet printer and dot-matrix printer is the print head.

Working of Inkjet Printer :-*There are different steps of printing process as following-

1.The print head is made up of small ink filled chamber, each attached to a nozzle, which is smaller than human hair.

2.An electrical pulse flow through a heating element which heats a thin layer of ink at the bottom of chamber. This makes the ink to boil and form a small bubble of vapor.

3.As this vapor bubble expands , it press the ink through the nozzle to form a droplet at the tip of nozzle.

4.The bubble forces droplet on to the paper, forming a small dot and a typical character is formed by a number of these tiny dots.

5.For color printing multiple cartridge of 3 basic colors- cyan, magenta and yellow are used. By mixing these 3 colors and a black color the inkjet printer can provide millions of colors.

●Working of inkjet printer :-

                     

                                       UNIT-12

                                   -: Keyboard :-

Keyboard :-•Keyboard is a input device which uses and arrangement of button for keys to act as mechanical levels all electrical switches. A keyboard typically correctors printed on the keys and each press of a key typically corresponds to a single return symbol or letter.

•At normal uses a keyboard is used to type a text into word processor, text editor or other program.

                                            

Types of Keyboard :-•One factor determining the size of a keyboard is the presence of duplicate keys such as a separate numeric key pack. Another factor determining the size of keyboard is size of keys and space between keys. One of the main component of any keyboard is switch keys. There are different technologies uses to make these switches as following.

•Types of keyboard :-

1.Membrane key switch.

2.Dome switch keyboard.

3.Scissor switch keyboard.

4. Capacitive keyboard.

5.Mechanical switch keyboard.

6.Bucking spring keyboard.

7.Half effect keyboard.

8.Laser keyboard.

9.Optical keyboard.

10.Roll up keyboard.

●Membrane key switch :-•There are two types of membrane based keyboard. Flat panel membrane keyboards and full travel membrane keyboards. Flat panel membrane keyboard are mostly found on applications like micro-waves ovens or photo copier. A common design consist of 3 layers. The top layer as the levels printed on the back, under this it has a special layer which fold the front and back layer a part so that they do not normally make electrically contact.

                                           

Dome switch keyboard :-•Dome switch keyboards are a high bridge of flat panel membrane and mechanical keyboards. They have two circuit boards connected together under a rubber or silicon keypad using either metal dome switches or politer formed domes.•This type of switches technology most commonly used in and hill controllers, mobile phones, small calculator and medical devices. Dome switch keyboard are also known as direct keyboards.

                                          

Scissor Switch keyboard :-•In this keyboard the keys are attached to the keyboard wire to plastic pieces that inter-lock in a scissor like fashion and snap to the keyboard and the key.

•This type of keyboard is mostly found on built in keyboard on laptop. These keyboards are generally quiet and the key require little force to press. Scissor switch keyboards are typically expensive.

                                          

Capacitive Keyboard:-•In this type of keyboards pressing the key changes the capacitance of a pattern of capacitors pads are like dome switch keyboards. The pattern consist of two D-shape capacitors pads for each switch, printed on a PCB and covered by a thin insulating film of solder mask which place of keyboard were the original IBM.

                                          

Mechanical switch keyboard :-•Mechanical switch keyboards use real switches under every key, depending on the construction of the switch. Such keyboards have varying response and travel time. These keyboards are better for a typist.

                                         

Bucking spring keyboard :-•In the bucking spring mechanism a top the switch is responsible for contact of key switch. This mechanism controls a small hammer that sticks a capacitive or membrane switch.                     

                                      

Half effect keyboard :-•A half effect keyboard use magnets and half effect sensors instead of a actual switch. It moves a magnet which is detective by the solid state sensor. They are used for ultra high reliable applications like nuclear systems or Air craft cock pits.

Laser keyboard :-•This types of keyboard is portable enough to be easily used with PDA and cellphone and many models have retractable ports and wireless. These keyboards are less user friendly then the cheapest membrane keyboard. 

                                    

Optical keyboard :-•An optical keyboard technology utilizes light emitting device and photo sensors to optically detect actuated keys.•The mechanism of optical keyboard is very simple, A light beam is sent from the emitter to the receiving sensor and actuated keys blocks reflect with the beam resulting is an identified key.

                                    

Roll up keyboard :-•Some keyboards are design to roll up i8n a light bundle, typically they are completely shielded in a rubber, making them water proof keyboards, like membrane keyboards they are reported to very hard to get used. 

                                    

Types of keys :-

•Keyboard consists different types of keys for different uses as following

•Alphanumeric.

•Modifier.

•Navigation and typing modes.

•System commands.

•Miscellaneous.•Function keys.

Alphanumeric :-•Alphabetical, numeric and punctuation keys are used in the same manner as a type writer. These keys used in text editors, many of these keys use to produce different symbols when modifier keys or shift keys are pressed. 

Modifier :-•Modifier keys are special keys that modify the normal action of another key, when two keys are pressed in combination. For example Alt + F4 in Microsoft windows will close the program in active window. The most widely used modifier key include the Ctrl key, Shift key and Alt key.

Navigation and Typing Mode :-•Navigation keys include a variety of keys which move the cursor to different position on the screen. Arrow keys move the cursor in a specified direction. Page Up and Page Down keys scroll the page, The Home key is use to return the cursor to beginning of and End key moves cursor at the end of line. The insert key is mainly used to switch between over type mode. The del key delete correctors. The backspace key delete the preceding correctors .

System Commands :-•The SysRq/Print Screen commands often share the same key. The SysRq was used in earlier system as a panic button to recovers from crash, The print screen command used to capture the entire screen and the user can paste that screen in clip board. The break key can be used by software in different ways.The Esc key is used to initiate an Escape sequence but today in Microsoft windows use a Esc as a shortcut in dialog boxes for quiet, Exit, cancel or abort.

Miscellaneous :-•The mostly keyboard have a numeric keypad to the right of the Alphabetic keyboard which contain numbers, basic mathematical symbols and few function keys. Some keyboards have power management keys for example- Power key, Sleep key and wake up key.

Function key :-•These are software specific keys for different purposes. Today keyboards contain F1 to F12 keys as a function key. 

                                                            UNIT 13 

Mouse :-A mouse is a hardware input device that was invented by Douglas Engelbart in 1963.The mouse allows an individual to control a pointer in a graphical user interface (GUI) and manipulate on-screen objects such as icon,file and folder.

Mechanical mouse :-A mechanical mouse is a computer mouse that contains a metal or rubber ball on its under side. When the ball is rolled in any direction, sensors inside the mouse detect this motion and move the on-screen mouse pointer in the same direction. The picture is an example of the bottom of a mechanical mouse with the ball removed. Today, this mouse has been replaced by the optical mouse.

Different part of mouse :-

                                

 The Optical Mouse :-With advances it mouse technology, it appears that the venerable wheeled mouse is in danger of extinction. The now-preferred device for pointing and clicking is the optical mouse.

                               

Developed by Agilent Technologies and introduced to the world in late 1999, the optical mouse actually uses a tiny camera to take 1,500 pictures every second.

Optical mouse :-The optical mouse is a computer mouse first introduced by Microsoft on April 19, 1999 that utilizes light-emitting diodes (LED) or laser to help track movement. These mice are identified by examining the bottom of the mouse. As seen in the picture the optical-mechanical mouse has a ball, and the optical mouse has a light emitting from the bottom.

Optical mouse(cont.) :-Drawbacks of some optical mice include working properly in rooms with bright lights and on some surfaces such as a glass table. However, in comparison to optical-mechanical mice, optical mice are a much better solution.

Optical mouse working :-In addition to having either a LED or laser, an optical mouse also has a tiny low-resolution camera that takes a thousand or more pictures every second. In the camera the complementary metal-oxide semiconductor (CMOS) sensor sends a signal to a Digital Signal Processor (DSP). The DSP can analyze each picture for pattern and light changes and then based off those changes moves the mouse cursor on your screen.

Cordless or wireless :-Cordless or wireless mice transmit data via infrared radiation, Bluetooth Hand Wi-Fi The receiver is connected to the computer through a serial or USB port, or can be built in (as is sometimes the case with Bluetooth and Wi-Fi).

Cordless working :-Although cordless devices requires no wires, they do require some device to broadcast a signal; for example, a Bluetooth mouse may require A USB Bluetooth transceiver to send and receive signals from the mouse. In addition to this, all wireless hardware devices require batteries.

Computer mouse ports :-Bluetooth: A computing and telecommunications industry specification that describes how different components such as mobile phones, computers or personal digital assistants can communicate with each other. Bluetooth is a RF technology that operates at 2.4 GHz, has an effective range of 32-feet (10 meters) (this range can change depending on the power class).

                               

PS/2 :-Often referred to as the mouse port or keyboard port, the PS/2 port was developed by IBM and is used to connect a computer MOUSE or KEYBOARD to an IBM compatible computer. The PS/2 port is a mini DIN plug that contains six pins and is still found on all IBM compatible computers today, however, is starting to be replaced by USB.

Data Interface :-The standard PS/2 type connector, as shown here:

                           

A typical PS/2 connector: Assume that pin 1 is located just to the left of the black alignment pin, and the others are numbered clockwise from there.

These pins have the following functions (refer to the above photo for pin numbering):

1.Data .

2.Unused .

3. Ground.

4.+5 volts.

5.Clock .

6.Unused .

Serial port :-An Asynchronous port on the computer used to connect a serial device to the computer and capable of transmitting one bit at a time. Serial ports are typically identified on IBM compatible computers as COM (communications) ports. For example, a mouse might be connected to COM1 and a modem to COM2.

                           

USB :- USB(universal serial bus) is a standard that was introduced in 1995 by intel, Compaq, Microsoft and other computer companies. USB 1.x is an external bus standard that supports data transfer rates of 12 Mbps and is capable of supporting up to 127 peripheral devices. The picture shows an example of a USB cable being connected into the USB port.

USB 2.0 :- USB 2.0, also known as hi-speed USB, was developed by Compaq, Hewlett Packard, Intel,Lucent, Microsoft, NEC and Philips and was introduced in 2001. Hi-speed USB is capable of supporting a transfer rate of up to 480 Mbps and is backwards compatible, meaning it is capable of supporting USB 1.0 and 1.1 devices and cables.

USB 3.0 :-USB 3.0 also known as SuperSpeed USB is the latest version of the USB protocol. Most new computers feature USB 3.0 ports built-in, offering data transfer speeds of up to 5 gigabits per second. USB 3.0 improved upon the USB 2.0 technology with speed and performance increases, improved power management and increased bandwidth capability (providing two unidirectional data paths for receiving and sending data at the same time).

Infrared :-A method of transferring data without the use of wires. A common example of an infrared (Ir) device is a TV remote. However, infrared is also used with computers with devices such as a cordless keyboard or mouse. The picture is an example of the Nintendo Wi-Fi remote and a good example of an infrared device

Bluetooth :-It has a transfer rate of 1 Mbps and through put of 721 Kbps. A good example of how Bluetooth could be used is the ability to connect a computer to a cell phone without any wires or special connectors. 

   UNIT-13

MONITOR :-*A monitor Is an electronic visual display for computers. The monitor comprises the display device, circuitry and an enclosure. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) thin panel, while older monitors used a cathode ray tube (CRT) about as deep as the screen size.

Technologies :-*Multiple technologies have been used for computer monitors, as following :

1.CRT (Cathode Ray  Tube).

2.LCD (Liquid Crystal Display).

3.OLED ( Organic Light Emitting Diode).

CRT :-*Cutaway rendering of a color CRT:

1.Three Electron guns (for red, green, and blue phosphor dots).

2.Electron beams.

3.Focusing coils.

4.Deflection coils.

5.Anode connection.

6.Mask for separating beams for red, green, and blue part of displayed image.

7.Phosphor layer with red, green, and blue zones.

8.Close-up of the phosphor-coated inner side of the screen.

                           

LCD :-*A LCD is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals. Liquid crystals do not emit light directly.

*LCDs are available to display arbitrary images or fixed images which can be displayed or hidden, such as preset words, digits, and 7-segment displays as in a digital clock. They use the same basic technology, except that arbitrary images are made up of a large number of small pixels, while other displays have larger elements.

*LCDs are used in a wide range of applications. They are available in a wider range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they do not suffer image burn-in.

*The LCD screen is more energy efficient and can be disposed of more safely than a CRT. Its low electrical power consumption enables it to be used in battery-powered electronic equipment. Liquid crystals were first discovered in 1888.

LCD :-*Reflective twisted nematic liquid crystal display.

1.Polarizing filter film with a vertical axis to polarize light as it enters.

2.Glass substrate with ITO electrodes. The shapes of these electrodes will determine the shapes that will appear when the LCD is turned ON. Vertical ridges etched on the surface are smooth.

3.Twisted nematic liquid crystal.

4.Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter.

5.Polarizing filter film with a horizontal axis to block/pass light.

6.Reflective surface to send light back to viewer. 

                           

OLED :-*An OLED is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound which emits light in response to an electric current. This layer of organic semiconductor is situated between two electrodes; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, portable systems such as mobile phones, handheld game consoles and PDAs.

*There are two main families of OLED: those based on small molecules and those employing polymers. Adding mobile ions to an OLED creates a light-emitting electrochemical cell (LEC) which has a slightly different mode of operation. OLED displays can use either passive-matrix (PMOLED) or active-matrix addressing schemes. Active-matrix OLEDs (AMOLED) require a thin-film transistor backplane to switch each individual pixel on or off, but allow for higher resolution and larger display sizes.

THIN-FILM-TRANSISTOR :-*TFT LCD is a variant of a liquid-crystal display (LCD) that uses thin-film transistor (TFT) technology to improve image qualities such as addressability and contrast. A TFT LCD is an active-matrix LCD, in contrast to passive-matrix LCDs or simple, direct-driven LCDs with a few segments.

*TFT LCDs are used in appliances including television sets, computer monitors, mobile phones, handheld video game systems, personal digital assistants, navigation systems and projectors.

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