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Network A system of interconnected computers and computerized peripherals such as printers is called computer network. This interconnection among computers facilitates information sharing among them. Computers may connect to each other by either wired or wireless media. A computer network consists of a collection of computers, printers and other equipment that is connected together so that they can communicate with each other.  

Network application
A Network application is any application running on one host and provides a communication to another application running on a different host, the application may use an existing application layer protocols such as: HTTP(e.g. the Browser and web server), SMTP(e.g. the email-client). And may be the application does not use any existing protocols and depends on the socket programming to communicate to another application. So the web application is a type of the network applications. 
There are lots of advantages from build up a network, but the th…



Most people use the term peripheral more loosely to refer to a device external to the computer case. You connect the device to the computer to expand the functionality of the system. For example, consider a printer. Once the printer is connected to a computer, you can print out documents. Another way to look at peripheral devices is that they are dependent on the computer system. For example, most printers can't do much on their own, and they only become functional when connected to a computer system. An expansion card (also known as an adapter card) is simply a circuit board you install into a computer to increase the capabilities of that computer. Expansion cards come in varying formats for different uses, but the important thing to note is that no matter what function a card has, the card being installed must match the bus type of the motherboard you are installing it into. For example, you can install a PCI network card into a PCI expansion slot only. A computer peripheral is a device that is connected to a computer but is not part of the core computer architecture. The core elements of a computer are the central processing unit, power supply, motherboard and the computer case that contains those three components. Technically speaking, everything else is considered a peripheral device. However, this is a somewhat narrow view, since various other elements are required for a computer to actually function, such as a hard drive and random-access memory (or RAM).
For today’s integrated components (those built into the motherboard), you might not need an adapter to achieve the related services, but you will still need to install drivers to make the integrated devices function with the operating system. As the trend toward More integrated components was maturing, many installers found most of the integrated components to be nonfunctional. A quick check in Device Manager showed a small col- lection of devices to be without their device drivers. Most motherboard manufacturers supply CD-ROM discs with their motherboards that contain all the device drivers needed to get the built-in electronics recognized by the operating system. Execution of the disc’s setup program generally results in all components working and Device Manager clearing its warnings. 
The following are the four most common categories of expansion cards installed today:
  •  Video 
  • Multimedia  
  • I/O 
  • Communications 


A video adapter (more commonly called a graphics adapter or even more commonly a video card) is the expansion card you put into a computer to allow the computer to display information on some kind of monitor. A video card is also responsible for converting the data sent to it by the CPU into the pixels, addresses, and other items required for display. Sometimes, video cards can include dedicated chips to perform some of these functions, thus accelerating the speed of display. 

At a basic level, video adapters that have a PCI interface operate sufficiently. However, because AGP and PCIe slots offer more resources to the adapter, most manufacturers and computer owners prefer not to use PCI slots for video adapters. Although you might be able to find the rare motherboard that still offers an AGP slot, PCIe is the preferred expansion slot for video card attachment. The technology on which PCIe was designed performs better for video than those on which AGP and PCI are based.


The most basic and prolific multimedia adapter is the sound card. TV tuner cards and video capture cards are newer multimedia adapters that continue to gain in popularity due to decreasing cost and the rise of the Internet as a forum for creative sharing. 

Sound Card 

Just as there are devices to convert computer signals into printouts and video information, there are devices to convert those signals into sound. These devices are known as sound cards. Although sound cards started out as plug-gable adapters, this functionality is one of the most common integrated technologies found on motherboards today. A sound card typically has small, round, 1⁄8 g jacks on the back of it for connecting microphones, headphones, and speakers as well as other sound equipment. Many sound cards used to have a DA15 game port, which can be used for either joysticks or MIDI controllers.  

Sound cards today might come with an RCA jack (see the section “Audio/ Video Jacks” later in this chapter).  This is decidedly not for composite video. Instead, there is a digital audio specification known as the Sony/Philips Digital Interface (S/PDIF). Not only does this format allow you to transmit audio in digital clarity, but in addition to specifying an RCA jack and coaxial copper cabling, it specifies optical fiber connectors (TOSLINK) and cabling for electrically noisy environments, further increasing transmission quality of the digital signal. 

TV Tuner Cards and Video Capture Cards 

TV Tuner Cards and Video Capture Cards
The TV tuner card is a class of internal and external devices that allows you to connect a broadcast signal, such as home cable television, to your computer and display the output on the computer monitor. TV tuner cards come in analog, digital, and hybrid varieties. Most TV tuner cards act as video capture cards as well. A video capture card can also be a stand- alone device and is often used to save a video stream to the computer for later manipulation or sharing.  Video-sharing sites on the Internet make video capture cards quite popular with enterprises and Internet socialites alike. TV tuner cards and video capture cards need and often come with software to aid in the processing of multimedia input. 


I/O cardI/O card is often used as a catchall phrase for any expansion card that expands the system to interface with devices that offer input to the system, output from the system, or both. Common examples of I/O are the classic serial (RS-232) and parallel (printer) ports and drive interface connections. A popular expansion card of the 1980s and early 1990s was known as the Super I/O card. This one adapter had the circuitry for two standard serial ports, one parallel port, two IDE (PATA) controllers, and one floppy controller. Some versions included other components, such as a game port. 

Often, if you want to use a SCSI hard drive in your system or a SCSI-attached printer or scanner, you have to install an expansion card that expands the motherboard’s capabilities to allow the use of SCSI devices. The drives and other devices then cable to the adapter, and the adapter performs the requisite conversion of the drive signals to those that the motherboard and the circuits installed on it could use. Today,  many server motherboards have SCSI controllers built in for such internal  hard drives, and everything else tends to use integrated USB and Fire-wire interfaces,  although expansion cards for these common  interfaces exist as well. 


Communications adapters give a computer the ability to transmit information to other devices that might be too distant to cable up to directly. Network adapters and modems are the two most popular types of communications adapter. Network adapters are generally used within the administrative domain of a home or enterprise and rely on other devices to relay their transmissions around the world.  In contrast, modems allow direct domestic or international communication between two devices across the Public Switched Telephone Network (PSTN). Although there are other devices in the PSTN, the service provider’s net- work appears as a cloud to the end stations, unlike the intermediate devices of a home or enterprise data network. 

Network Interface Card (NIC)

Network Interface Card (NIC)
A network interface card (NIC) is an expansion card that connects a computer to a network so that it can communicate with other computers on that network. NIC can also stand for network interface controller.  

It translates the data from the parallel data stream used inside the computer into the serial data stream that makes up the frames used on the network. It has a connector for the type of expansion bus on the motherboard (PCIe, PCI, and so on) as well as a connector for the type of network (such as fiber connectors, RJ-45 for UTP, antenna for wireless, or BNC for legacy coax). In addition to physically installing the NIC, you need to install drivers for the NIC in order for the computer to use the adapter to access the network.  

i. Wireless NICs

Wireless NICsWireless NICs have the unique characteristic of requiring that you configure their connecting device before configuring the NIC. Wired NICs can generally create a link and begin operation just by being physically connected out of the box to a hub or switch. The wireless access point or ad hoc partner computer must also be configured before secure communication, at a minimum, can occur by using a wireless NIC. 

ii. Cellular Cards

Cellular CardsAlmost every cellular service provider offers a line of adapters that can be installed into or inserted on the outside of desktop and laptop computers. In addition, depending on your service plan, most smartphones can be tethered to your computer and used as a cellular gateway. Very often, the cellular adapter comes with a setup program that configures the card for the service provider’s network. From that point,  anytime you are in a cellular service area, you can use the adapter to gain access to the Internet  through the provider  or by roaming  on the network of a partner or competitor with which an agreement  has been reached in that area. 


Any computer that connects to the Internet using an analog dial-up connection needs a modem, or modulator/demodulator. A modem is a device that converts digital signals from a computer into analog signals that can be transmitted over phone lines and back again. These expansion card devices have one connector for the expansion bus being used (PCIe, PCI, and so on) and another for connection to the telephone line. Actually this is primarily so that a phone can gain access to the same wall jack that the computer connects to without swapping their cords. Keep in mind, though, that you won’t be able to use the phone while the computer is connected to the Internet.  

Riser Cards

Riser CardsAn alternative motherboard form factor, known as New Low-Profile Extended (NLX),or one of its offshoots  have been used in some types of low-profile cases. NLX places the expansion slots sideways on a special riser card to use the reduced vertical space optimally. Adapter cards that normally plug into expansion slots vertically in other motherboards plug in parallel to the motherboard, so their second most demanding dimension does not affect case height.  
Riser technology also serves to free up valuable motherboard space for circuitry that cannot or should not be placed on adapters. Without the use of the riser, the motherboard would need to be made larger to accommodate the same circuitry. 

Identifying Characteristics of Connectors and Cables

Now that you’ve learned the various types of items found in a computer, let’s discuss the various types of ports and cables used with computers. A port is a generic name for any connector on a computer or peripheral into which a cable can be plugged. A cable is simply a way of connecting a peripheral or other device to a computer using multiple copper or fiber-optic conductors inside a common wrapping or sheath.  Typically, cables connect two ports: one on the computer and one on some other device. 

Let’s take a quick look at some of the different styles of port connector types as well as peripheral port and cable types. We’ll begin by looking at peripheral port connector types. 

 Device Connector Types

 Computer ports are interfaces that allow other devices to be connected to a computer. Their appearance varies widely, depending on their function. In this section we’ll examine the following types of peripheral ports: 

  • D-sub-miniature 
  • RJ-series 
  • Other types 

D-sub-miniature Connectors

D-sub-miniature ConnectorsD-sub connectors, for a number of years the most common style of connector found on computers, are typically designated with DXn, where the letter X is replaced by the letters A through E, which refer to the size of the connector, and the letter n is replaced by the number of pins or sockets in the connector. D-sub connectors are usually shaped like a trapezoid and have at least two rows of pins with no other keying structure or landmark. 


Serial port

Connector on a serial cable

Serial port or connector on a parallel cable

Parallel port, or connector on a serial cable

Game port or MIDI port

Connector on a game peripheral cable or MIDI cable

Video  port (has three rows of five pins as opposed to two  rows)

Connector on a monitor cable











Registered jack (RJ) connectors are most often used in telecommunications. The two most common examples of RJ ports are RJ-11 and RJ-45. RJ-11 connectors are used most often on flat satin cables in telephone hookups; your home phone jack is probably an RJ-11 jack. The ports in older external and internal analog modems are RJ-11. RJ-45 connectors, on the other hand, are larger and most commonly found on Ethernet networks that use twisted-pair cabling. Your Ethernet NIC likely has an RJ-45 jack on it. RJ-45 is a widely accepted description for the larger connectors, it is not correct.  Generically speaking, Ethernet interfaces are 8-pin modular connectors, or 8P8C connectors, meaning there are eight pin positions, and all eight of them are connected, or used. RJ-45 specifies 

The physical appearance of the connector and also how the contacts are wired from one end to the other.  Surprisingly the RJ-45 specification does not match the TIA T568A and T568B wiring standards used in data communications. 

Other Types of Ports

There are many other types of ports that are used with computers today, including these:
  • Universal Serial Bus (USB) 
  • IEEE 1394 (Fire-wire) 
  • Infrared 
  • Audio jacks 
  • PS/2 (mini-DIN) 
  • Centronics 

Universal Serial Bus (USB)

Universal Serial Bus (USB)Most computers built after 1997 have one or more flat ports in place of one DE9M serial port. These ports are Universal Serial Bus (USB) ports, and they are used for connecting multiple (up to 127) peripherals to one computer through a single port (and the use of multi-port peripheral hubs). USB version 1.x supports data rates as high as 12Mbps (1.5MBps).  USB 2.0 supports data rates as high as 480Mbps (60MBps), 40 times that of its predecessor.  USB 3.0 boasts data rates of 5Gbps, more than 10 times the rate of USB 2.0.

Because of USB’s higher transfer rate, flexibility, and ease of use, most devices that in the past used serial or parallel interfaces now come with USB interfaces.  It’s rare to see a newly introduced PC accessory with a standard serial interface.  For example, PC cameras used to come as standard serial-only interfaces.  Now, USB and Fire-wire are the preferred interfaces. 

IEEE 1394 (Fire-wire)

While not as prevalent as USB ports, one other port has crept into the mainstream and is included as a standard attachment in small numbers, often only one, on motherboards and laptops. That port is the IEEE 1394 port, more commonly known as a Fire-wire port.  Its popularity is due to its ease of use, isochronous (synchronized clock) mode, and very high (400Mbps to 3.2Gbps and higher) transmission rates. 


Many years ago, increasing numbers of people became fed up with being tethered to their computers by cords. As a result, many computers (especially portable computing devices like laptops and PDAs) hit the market with infrared ports to send and receive data.  Modern com- putters use radio frequency (RF) technologies, such as Bluetooth and Wi-Fi, to accomplish the same and more. 

Common Peripheral Cables and Their Interfaces

An interface is a method of connecting two dissimilar items together. A peripheral interface is a method of connecting a peripheral or accessory to a computer, including the specification of cabling, connector and port type, speed, and method of communication used. The most common interfaces used in PCs today include (in no particular order): 
  • Drive interfaces 
  • SCSI 
  • Parallel 
  • Serial 
  • USB 
  • IEEE 1394 (Fire-wire) 
  • RJ-45 
  • Audio (RCA and TOSLINK) 
  • PS/2 

Floppy and Hard Disk Connectors

Floppy and Hard Disk Connectors
Floppy disk drive interfaces allow floppy disk drives (FDDs) and certain other devices, such as some internal tape drives, to be connected to the motherboard, and similarly, hard disk drive interfaces do the same for hard disks and optical drives, among others.  The interfaces consist of circuitry and a port, or header. Many motherboards produced today lack a header for FDD attachment. Almost all, however, still provide non-SCSI hard disk inter- faces on the motherboard, with the latest version of SATA being the most popular.
Hard Disk
The 40-pin ATA header transfers multiple bits of data between the drive and motherboard in parallel, hence the name Parallel ATA. SATA, in comparison, which came out later and prompted the retroactive PATA moniker, transfers data in series, allowing a higher data throughput because there is no need for the more advanced parallel synchronization of data signals. The SATA headers are vastly different from the PATA headers.   

Common Ports and Connectors

For a computer to be useful and have as much functionality as possible, there must be a way to get the data into and out of it. Many different ports are available for this purpose. This section continues the discussion of port and connector types started earlier in the chapter but introduces additional information on those already mentioned and other interfaces. Briefly, the seven most common types of ports you will see on a computer are Universal Serial Bus (USB), Fire-wire/IEEE 1394, eSATA, video, Ethernet, digital/analog sound in/out, and PS/2 keyboard and mouse.  
  • DC power in 
  • Analog modem RJ-11 
  • Ethernet  NIC RJ-45 
  • S-video out 
  • DVI-D (dual-link)   
  • SVGA out 
  • Parallel  
  • Standard serial        
  • S/PDIF  
  • USB 

The Classic Game Port 

The game port can be used to connect to Musical Instrument Digital Interface (MIDI) devices as well. Game ports connect such peripheral devices to the computer using a DA-15F connector. Legacy sound cards often included a game port.  Devices that once connected to the game port have evolved, for the most part, into USB-attached devices. 

Analog Sound Jacks

These jacks are known  as 1 ⁄ 8 g (3.5mm)  stereo mini jacks,  so called for their size and the fact that they make contact  with both the left and right audio channels through their tip, rings (if they have any), and sleeve. 

Shown in the photo is a six-jack setup capable of 8-channel audio, also known as 7.1 surround sound. The 7 represents the seven full-bandwidth channels and the 1 represents the one low frequency effects (LFE) channel, most often attached to the sub-woofer. 

Parallel Interfaces

For many years, the most popular type of interface available on computers was the parallel interface.  Parallel communications take the interstate approach to data communications. Normally, interstate travel is faster than driving on city roads.  This is the case mainly because you can fit multiple cars going the same direction on the same highway by using multiple lanes. On the return trip, you take a similar path, but on a completely separate road.  The parallel printer interface transfers data 8 bits at a time over eight separate transmit wires inside a parallel cable (1 bit per wire). 

Normal parallel interfaces use a DB25 female connector on the computer to transfer data to peripherals. Parallel ports are faster than the original serial ports, which were also once used for printers in electrically noisy environments or at greater distances from the computer. However, the advent of USB has brought serial—fast serial—back to the limelight. As it turns out, firing 1 bit at a time leads to faster bit rates than babysitting a parallel procession of bits. 

Standard Parallel Ports

The standard parallel port only transmits data out of the computer. It cannot receive data (Except for a single wire carrying a Ready signal). The standard parallel port was found on the original IBM PC, XT, and AT. It can transmit data at only 150KBps and was most commonly used to transmit data to printers.  This technology also had a maximum trans- mission distance of 10 feet. 

Bidirectional Parallel Ports

As its name suggests, the bidirectional parallel port has one important advantage over a standard parallel port: It can both transmit and receive data.  These parallel ports are capable of interfacing with such devices as external CD-ROM drives and external parallel port backup drives (Zip, Jaz, and tape drives). Most computers made since 1994 that included a parallel printer port had this bidirectional parallel port. 

Parallel Interfaces and Cables

Most parallel interfaces use a DB25 female connector, as shown earlier in this chapter.  Most parallel cables use a DB25 male connector on one end and either a DB25 male connector or, more commonly, a Centronics36 connector on the other.  The original printer cables typically used the DB25M–to–Centronics-36 configuration. Inside a parallel cable, eight wires are used for transmitting data so that 1 byte can be transmitted at a time.


If standard parallel communications were similar to taking the interstate, then RS-232 serial communications were similar to taking a country  road.  In serial communications, bits of data are sent one after another (single file, if you will) down one wire, and they return  on a different wire in the same cable. Three main types of serial interfaces are available today: standard serial (RS-232), Universal Serial Bus (USB), and Fire-wire (IEEE 1394).  USB and Fire-wire use increased signaling frequencies to overcome serial’s stigma and join other serial technologies, such as PCIe and SATA, as front-runners in data communications. 

Standard Serial 

Almost every computer made since the original IBM PC has at least one serial port.  These computers are easily identified because they have either a DE9 or DB25 male port. Standard serial ports have a maximum data transmission speed of 57Kbps and a maximum cable length of 50 feet. 

Serial cables come in two common wiring configurations: standard serial cable and null modem serial cable. A standard serial cable is used to hook various peripherals such as modems and printers to a computer. A null modem serial cable is used to hook two computers together without a modem.  The transmit-centric pins on one end are wired to the receive-centric pins on the other side, so it’s as if a modem connection exists between the two computers but without the need for a modem.

Common serial cable configurations

First Connector

Second Connector
DE9 female

DB25 male
Standard modem cable
DE9 female

DE9 male
Standard serial extension cable
DE9 female

DE9 female
Null modem cable
DB25 female

DB25 female
Null modem cable
DB25 female

DB25 male
Standard serial cable or standard serial extension cable

Universal Serial Bus

(USB) USB cables are used to connect a wide variety of peripherals to computers, including key- boards, mice, digital cameras, printers, and scanners.  Not all USB cables maximize the potential of all USB ports.  USB 1.x cables cannot provide USB 2.0 and 3.0 performance; USB 2.0 cables cannot provide USB 3.0 performance. Good or bad, depending on how you look at it, the interfaces accept all cable connectors. So, ensuring that your cable is built to the specification you intend to use, whether version 2.0 or 3.0, is of utmost importance. Otherwise, the connected device will have to fall back to the maximum version supported by the cable. This is usually not an issue, except for the lost performance, but some high- performance devices will refuse to operate at reduced levels. 

USB speed limitations


Maximum Speed
Speed Trade Name
USB 1 .0 /1 .1

Full Speed
USB 2 .0

High Speed
USB 3 .0

5Gbps (5000Mbps)
Super Speed

The USB technology is fairly straightforward. Essentially, it was designed to be Plug and Play—just plug in the peripheral and it should work, providing the software is installed to support it. Many standard devices have drivers built into the common operating systems. More complex devices come with drivers to be installed before the component is connected. The USB cable varies most based on the USB peripheral connector on the external-device end. Because there can be quite a number of USB devices on a single system, it helps to have a scheme to clarify their connectivity. The USB standard specifies two broad types of connectors.  They are designated Type A and Type B connectors. A standard USB cable has some form of Type a connector on one end and some form of Type B connector on the other end. Let’s have a look on various USB connectors. 
  • Type A  
  • N-Standard Mini-B 
  • Type B 
  • Alternate Mini-B 

USB cable-length limitations


Maximum Cable Length
Total Cable with  Five Hubs
USB 1 .0 /1 .1

USB 2 .0

USB 3 .0


In addition to the cable length difference between USB 2.0 and 3.0, there are a host of other differences between these specifications.  The following items outline some of the primary differences. 


USB 3.0 requires that each pair in the cable assembly be shielded to withstand the electromagnetic interference (EMI) inherent with transmissions at higher frequencies. 


 Although all connectors are compatible with all receptacles, to attain Super Speed performance, Super Speed connectors with five additional pins must be used on cables and receptacles.  These pins do not obstruct the four legacy pins required for backward compatibility. Instead, they sit farther back and are accessible only to compatible interfaces. 

Bursting and streaming

USB 2.0 does not support bursting, the low-duration, excessively fast transmission of data, nor does it support streaming, the continuous flow of data between two endpoints once the flow has begun. USB 3.0 supports continuous bursting as well as streaming. 


USB 2.0 is a half-duplex technology, meaning that all devices must share a common bandwidth, making overall performance appear sub-par.  USB 3.0, on the other hand, supports dual simplex communications pathways that collectively imitate full-duplex transmission, where devices at both ends of the cable can transmit simultaneously. 

Media access method

USB 2.0 peripheral devices must wait until polled by the host before transmitting data.  USB 3.0 endpoints use an asynchronous transmission mechanism, similar to that of Ethernet, where data is transmitted at will. 

Host control

The host (computer system) is the only device in the USB 2.0 specification that can control power management. The endpoints are the only devices that can participate in error detection and recovery as well as flow control. USB 3.0 endpoints can all control when they enter low-power mode to conserve power.  Error handling and flow control are performed on each link in USB 3.0, not just at the endpoints. 

Power   USB 2.0 provides a maximum of 100 mill amperes (mA) of current at low power and 500mA at high power.  USB 3.0 provides 150mA and 900mA, respectively, allowing for the direct powering of some of the same component types that Fire-wire is capable of powering but that USB 2.0 is not.Through the use of a 7-bit identifier, providing 27 = 128 possible addresses, no more than 127 devices, including hubs, should be connected back to a single USB host controller in the computer, not that you would ever want to approach this number.  The 128th identifier, the highest address, is used for broadcasting to all endpoints. No interconnection of host controllers is allowed with USB; each one and its connected devices are isolated from other host controllers and their devices. As a result, USB ports are not considered network- able ports.  Consult your system’s documentation to find out if your USB ports operate on the same host controller. From the perspective of the cable’s plug, Type A is always oriented toward the system from the component. As a result, you might notice that the USB receptacle on the computer system that a component cables back to is the same as the receptacles on the USB hub that components cable back to. The USB hub is simply an extension of the system and becomes a component that cables back to the system. Each hub takes one of the 127 available addresses. Type B plugs connect in the direction of the peripheral component. Therefore, you see a single Type B interface on the hub as well as on the peripheral endpoints to allow them to cable back to the system or another hub. Although they exist, USB cables with both ends of the same type, a sort of extension cable, are in violation of the USB specification. Collectively, these rules make cabling your USB subsystem quite straightforward. 

IEEE 1394 (Fire-wire)

The IEEE 1394 interface is about two things, if nothing else: speed and efficiency. Its first iteration, now known as Fire-wire 400, has a maximum data throughput of 400Mbps in half duplex.  Although the numbers imply that USB 2.0 at 480Mbps might outperform Fire-wire 400, the truth is that Fire-wire allows a closer saturation of the bandwidth by its devices due to its different encoding mechanism.  USB devices are lucky to achieve half of their bus’s rated bandwidth during sustained operation. The other major difference between the two technologies is the amount of power accessible to Fire-wire devices. Whereas USB provides less than an ampere of current at 5VDC, Fire-wire specifications allow for the provision of 1.5A at up to 30VDC (and slightly more in some implementations). This production of 45W of power allows for larger devices to be powered by the Fire-wire interface, obviating the need for separate external power. The next iteration, Fire-wire 800 (specified under IEEE 1394b), has a maximum data throughput of 800Mbps and works in full duplex.  Fire-wire 400 carries data over a maxi- mum cable length of 4.5 meters with a maximum of 63 devices connected to each interface on the computer. Using new beta connectors and associated cabling, including a fiber-optic solution, Fire-wire 800 extends to 100 meters. When implemented over copper, Fire-wire 800, like Fire-wire 400, is limited to 4.5m cable runs. IEEE 1394c standardized the running of Fire-wire over the same Category 5e infrastructure that supports Ethernet, including the use of RJ-45 connectors. IEEE 1394b also allows for 1.6Gbps (S1600) and 3.2Gbps (S3200) implementations. 

Although most people think of Fire-wire as a tool for connecting their digital camcorders to their computers, it’s much more than that.  Because of its high data transfer rate, it is being used more and more as a universal, high-speed data interface for things like hard drives, optical drives, and digital video editing equipment.


The RCA cable is a simple coaxial cable. There are two connectors, usually male, one on each end of the cable. There are two contacts on each connector, the ground ring and the positive data pin in the middle. The male connector connects to the female connector on the equipment. An RCA male-to-RCA female connector is also available; it’s used to extend the reach of audio or video signals. 

PS/2 (Keyboard and Mouse)

The most important input device for a PC is the keyboard. All PC motherboards contain some sort of connector that allows a keyboard to be connected directly to the motherboard through the case. There are two main types of wired keyboard connectors. Once, these were the AT and PS/2 connectors. Today, the PS/2-style connector remains somewhat popular, but it is quickly being replaced by USB-attached keyboards. The all-but-extinct original AT connector is round, about 1⁄2 g in diameter, in a 5-pin DIN configuration. Figure 3.32 shows an example of the AT-style keyboard connector. The PS/2 connector is a smaller 6-pin mini-DIN connector. Many new PCs you can purchase today contain a PS/2 keyboard connector as well as a PS/2 mouse connector right above it on the motherboard. 

Video Display Cables and Connectors

While the analog VGA-spawned standards might keep the computing industry satisfied for years to come yet, the sector in the market driving development of non-VGA specifications has become increasingly more prevalent.  These high-resolution, high-performance junkies approach video from the broadcast angle. They are interested in the increased quality of digital transmission. For them, the industry responded with technologies like DVI and HDMI.  The computing market benefits from these technologies as well. DVI interfaces on graphics adapters and laptops became commonplace. In increasingly more cases, HDMI interfaces take adapters to the next generation. Other consumers desire specialized methods to connect analog display devices by split- ting out colors from the component to improve quality or simply to provide video output to displays not meant for computers. For this group, a few older standards remain viable: component video, S-video, and composite video. The following sections present the details of these five specifications. 


In an effort to leave analog VGA standards and return  to digital video, which can typically be transmitted farther  and at higher quality than analog,  a series of connectors known  collectively as Digital Visual (or Video) Interface (DVI)  connectors was developed for the technology of the same name. These digital interfaces offer much higher performance than the original digital standards, such as CGA and EGA. At first glance, the DVI connector might look like a standard D-sub connector, but on closer inspection, it begins to look somewhat different.  For one thing, it has quite a few pins, and for another, the pins it has are asymmetrical in their placement on the connector. 

There are three main categories of DVI connectors

DVI-A    An analog-only connector. The source must produce analog output, and the monitor must understand analog input.
DVI-D    A digital-only connector. The source must produce digital output, and the monitor must understand digital input.
 DVI-I   A combination analog/digital connector. The source and monitor must both support the same technology, but this cable works with either a digital or an analog signal. 


High-Definition Multimedia Interface (HDMI)  is an all-digital technology  that advances the work of DVI to include the same dual-link  resolutions using a standard HDMI  cable but with higher motion-picture frame rates and digital audio right on the same connector. HDMI cabling also supports an optional Consumer Electronics Control (CEC) feature that allows transmission of signals from a remote control unit to control multiple devices with- out separate cabling to carry infrared signals. 

HDMI is compatible with DVI-D and DVI-I interfaces through proper adapters, but HDMI’s audio and remote-control pass-through features are lost. Additionally, 3D video sources work only with HDMI.


Two main forms of coaxial cable are used to deliver video from a source to a monitor or television. One of them is terminated by RCA or BNC plugs and tends to serve a single frequency, while the other is terminated by F connectors, those seen in cable television (CATV) settings, and tends to require tuning/demodulation equipment to choose the frequency to display. The terms that refer to whether a single frequency or multiple frequencies are carried over a cable are base-band and broadband, respectively. 


With the capability of today’s data networks, both compressed and even uncompressed audio and video can be digitized and sent over an IP network in packet form. The physical and data-link connectivity is often implemented through devices that connect through a standard Ethernet network. Care must be taken that this new application for the network does not obstruct the normal flow of data or even the possibly recently added voice over IP (VoIP) traffic. As with VoIP applications, quality of service (QoS) must be implemented and supported throughout the data network or audio/video (A / V) quality will surely suffer. 

Types of Peripheral Devices 

There are many different peripheral devices, but they fall into three general categories: 
1. Input devices, such as a mouse and a keyboard. 
2. Output devices, such as a monitor and a printer. 
3. Storage devices, such as a hard drive or flash drive. 

Input Devices:

An input device for a computer allows you to enter information. The most fundamental pieces of information are keystrokes on a keyboard and clicks with a mouse. These two input devices are essential for you to interact with your computer. Many other input devices exist for entering other types of information, such as images, audio and video. Input devices represent one type of computer peripheral - the other two types are output devices and storage devices. Following are few of the important input devices which are used in a computer: 
  • Keyboard  
  • Mouse 
  • Joy Stick 
  • Light pen 
  • Track Ball 
  • Scanner 
  • Graphic Tablet 
  • Microphone 
  • Magnetic Ink Card Reader(MICR) 
  • Optical Character Reader(OCR) 
  • Bar Code Reader 
  • Optical Mark Reader(OMR) 


A computer keyboard is an input device used to enter characters and functions into the computer system by pressing buttons, or keys. It is the primary device used to enter text. A keyboard typically contains keys for individual letters, numbers and special characters, as well as keys for specific functions. A keyboard is connected to a computer system using a cable or a wireless connection. Most keyboards have a very similar layout. The individual keys for letters, numbers and special characters are collectively called the character keys. The layout of these keys is derived from the original layout of keys on a typewriter. The most widely used layout in the English language is called QWERTY, named after the sequence of the first six letters from the top left. Other sets of keys common to almost all keyboards are entering and editing keys (e.g., Enter, Delete, Insert), modifier keys (e.g., Control, Shift), navigation keys (e.g., arrows for up, down, left, right) and lock keys (e.g., Caps Lock). Additional keys are very operating system specific (such as the Windows and Apple keys). Most keyboards also include a set of function keys at the top (F1, F2, etc.). The function keys typically perform a very specific task within a particular software application. So, what they do may depend on what you are doing on your computer at the time. Most keyboards for desktop computers also contain a separate numeric keypad to the right. Even though there are numeric keys already in a row near the top, having them all close together makes it faster to enter numeric data. On smaller keyboards, like those on most laptops, these numeric keypads are typically no longer present due to space constraints. 

Mouse: A mouse is a small device that a computer user pushes across a desk surface in order to point to a place on a display screen and to select one or more actions to take from that position. The mouse first became a widely-used computer tool when Apple Computer made it a standard part of the Apple Macintosh. Today, the mouse is an integral part of the graphical user interface (GUI) of any personal computer. 

Traditional mouse

Traditional computer mouse button will be the most affordable, when they make use of a simple construction. They connect to your personal machine utilizing the mouse port, and some mouse for Apple computers use a USB connection. Most mouse include a USB connection for those who love the USB port within the mouse port. No special application is needed, while you need to reboot after connecting in case you are employing an older version of Windows. This kind of mouse does need to be periodically disassembled for cleaning. You should make use of a lint-free, static-free cloth for cleaning. It will eliminate harm to your mouse preventing any bothersome lint buildup. 

Optical mouse

Optical mouse have become more commonplace. They exercise efficiently, because they lack the ball found in traditional mouse. The majority are built to be ergonomic, so you are able to make use of them very comfortably. There’re especially appropriate users with cts or arthritis. These mouse are less vulnerable to collecting dust than traditional mouse are and require less cleaning. Most optical mouse hook up to your computer through the USB port. Special software usually isn’t necessary if you do not need advanced functions enabled for the mouse. You are able to enable any special functions that you want your mouse to accomplish when using the driver CD that had the mouse. 

➤ Wireless mouse

Wireless mouse provide capability of connecting without cables. That is very useful for gamers as well as others who want room to freely move their mouse. A button ‘talks’ to the computer with the infrared port that you just attach yourself. Some newer laptops consist of built-in infrared ports where you can start employing the mouse without special hardware. These sorts of mouse include the necessary driver software. You’ll normally be capable to start using your brand-new mouse during first minutes. Wireless mouse are optical, taking into account easier movement. Many wireless mouse are purchased plus a wireless keyboard. When you’ve got a large enough monitor, you are able to safely sit well back through the computer and still have the capacity to apply it efficiently. 

➤ Laptop mouse

Laptop mouse have numerous of identical features as desktop mouse. They give a more compact design that’s well-suited to smaller spaces that laptops are utilized in. These mouse are ideal for laptop users unaccustomed to track pads. Additionally they be useful if your track pad fails and you poses zero chance to change it instantly. Laptop mouse use a retractable cord having a USB connection or may include wireless connection. 


An input device that allows the user to control a character or machine in a computer program. They look similar to the control device you would find on an arcade game. For example, a joystick allows an individual to move an object in a game; such as navigating a plane in a flight simulator. A joystick is a type of gaming controller that may mimic the appearance of an aircraft flight stick. One typically consists of a stick, mounted on a base of some kind that can be articulated in two or three directions. One of the oldest control methods for video games, joysticks are prevalent on arcade machines and may also be available for home use. Most home video game systems have had a variety of joysticks available as optional peripherals, with older systems even using them as the primary controller. They are often sought out in situations where a game requires precise inputs and a great deal of control, such as in flight simulators or games in the fighting genre.  While the joystick is typically an analog input device, digital versions have also existed. An analog joystick typically works by transmitting an angle reading to a video game system or computer. This way, the device can detect where the stick is moved, along both x and y axes, at any time. Models with a z axis are also able to transmit this additional date along with the x and y positions. 

Analog Joystick

Analog joysticks often have what may be known as gates. These are a part of the movement mechanism, and allow the user of the stick to easily lock it into four or eight different cardinal positions. While the movement remains analog, this may be useful to some people that use a joystick for fighting-type games. Round gates may also be available, and it is often possible to modify a joystick with a different style of gate according to personal preference. 

Digital Joystick

Digital joysticks operate in much the same way as the analog variety, though they are only capable of reporting that a movement has occurred, rather than the distance the stick was moved in that direction. These may still be capable of reporting in-between movements, such as an up-left movement, a down-right movement, or anything in between. They were commonly seen in many of the earliest home video game systems. 


A scanner is a device that captures images from photographic prints, posters, magazine pages, and similar sources for computer editing and display. Scanners come in hand-held, feed-in, and flatbed types and for scanning black-and-white only, or color. Very high resolution scanners are used for scanning for high-resolution printing, but lower resolution scanners are adequate for capturing images for computer display. 

➤ Flatbed Scanners

The most common desktop scanners resemble copy machines, in that the item being scanned rests on a glass plate while the scanning head moves underneath it. These flatbed scanners are versatile because they can scan flat originals of various sizes, and they can even scan small three-dimensional objects. Most flatbed scanners require a transparency adapter with a separate light source in order to scan slides, x-rays, and other transparent originals. And unless the user is willing to place each page on the scanner individually, they require an automatic document feeder to handle large numbers of documents.  

 ➤ Sheet-fed Scanners

Over the last few years, personal sheet-fed scanners have grown in popularity. These units are more like a fax machine than a copier, because they move the page being scanned past the scanning head, rather than the other way around. Some sheet-fed scanners only scan a single sheet of paper at a time, while others come with built-in document feeders that can scan multiple-page documents unattended. Sheet-fed scanners also tend to be less exact than their flatbed counterparts, because of the difficulty of moving a sheet of paper without introducing distortions. Still, a sheet-fed scanner is a good choice for handling paperwork without giving up much desk space.   

 Slide Scanners

Some items demand special handling during scanning. Slides, for instance, require a scanner that passes light through the image rather than reflecting off light off it. Because of their small size, slides also need to be scanned on a unit with very high resolution (in other words, a lot of eyes on the scanning head).To meet these requirements, several manufacturers have developed dedicated scanners that handle only 35mm slides. These devices are usually much more expensive than flatbed or sheet-fed scanners, and are much less versatile, but they are still the right choice for those who need to make high-quality scans of more than a few slides.  

Drum Scanners

Before the advent of desktop scanning, most images were loaded into computers through drum scanners. Expensive and difficult to operate, these units were found primarily in color prepress companies. Technicians there would carefully mount originals on a glass cylinder, which would then be rotated at high speeds around a sensor located in the center. Today, drum scanners remain the best high-end choice, but while their prices have come down significantly, they remain expensive in comparison to flatbed or sheet-fed scanners. Their advantage lies in the fact that they typically use photo-multiplier tubes (PMTs), which are more sophisticated sensors than the charge-coupled devices (CCDs) and contact image sensors (CISs) used in other kinds of scanners. That, and the fact that the original is rotated past the PMTs again and again at high speed, makes drum scanners important professional tools.  

Light pen

A light-sensitive stylus wired to a video terminal used to draw pictures or select menu options. The user brings the pen to the desired point on screen and presses the pen button to make contact. Contrary to what it looks like, the pen does not shine light onto the screen; rather, the screen beams into the pen. Screen pixels are constantly being refreshed. When the user presses the button, the pen senses light, and the pixel being illuminated at that instant identifies the screen location.  

Track Ball

 A trackball is a computer cursor control device used in many notebook and laptop computers. The trackball is usually located in front of the keyboard toward the user. Essentially, the trackball is an upside-down mouse that rotates in place within a socket. The user rolls the ball to direct the cursor to the desired place on the screen and can click one of two buttons (identical to mouse buttons) near the trackball to select desktop objects or position the cursor for text entry. 

Graphics Tablet

Alternatively referred to as a drawing tablet and pen tablet, a graphics tablet is a hardware input device that enables an artist to draw or sketch digitally using a pen. They are helpful because they provide a more natural and precise feel than a standard computer mouse.  


A microphone is a device that captures audio by converting sound waves into an electrical signal. This signal can be amplified as an analog signal or may be converted to a digital signal, which can be processed by a computer or another digital audio device. While all microphones (or "mics") serve the same basic function, they can capture audio in several different ways.

Magnetic Ink Card Reader (MICR)

Short for Magnetic-Ink Character Recognition, MICR is a font capable of recognition using magnetically charged ink. Computers equipped with the right hardware and software can print or read the character printed in such ink. MICR font is commonly used to print checks, deposit slips, mortgage coupons, etc. There are several MICR fonts, the MICR E-13B font is used in the Canada, Panama, Puerto Rico, UK, and the United States. The MICR CRC-7 was created according to the ISO standards and is a font used in France, Mexico, Spain, and most other Spanish speaking countries. 

OCR (Optical character recognition)

OCR (optical character recognition) is the recognition of printed or written text characters by a computer. This involves photo scanning of the text character-by-character, analysis of the scanned-in image, and then translation of the character image into character codes, such as ASCII, commonly used in data processing. In OCR processing, the scanned-in image or bitmap is analyzed for light and dark areas in order to identify each alphabetic letter or numeric digit. When a character is recognized, it is converted into an ASCII code.Special circuit boards and computer chips designed expressly for OCR are used to speed up the recognition process. OCR is being used by libraries to digitize and preserve their holdings. OCR is also used to process checks and credit card slips and sort the mail. Billions of magazines and letters are sorted every day by OCR machines, considerably speeding up mail delivery. 

Bar Code Reader

A bar-code reader (or bar-code scanner) is an electronic device that can read and output printed bar-codes to a computer. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all bar-code readers contain decoder circuitry analyzing the bar-code's image data provided by the sensor and sending the bar-code's content to the scanner's output port.  

Optical Mark Reader (OMR)

Short for Optical Mark Reading or Optical Mark Recognition, OMR is the process of gathering information from human beings by recognizing marks on a document. OMR is accomplished by using a hardware device (scanner) that detects a reflection or limited light transmittance on or through piece of paper. OMR allows for the processing of hundreds or thousands of physical documents per hour. For example, students may recall taking tests or surveys where they filled in bubbles on paper (shown right) with pencil. Once the form had been completed, a teacher or teacher's assistant would feed the cards into a system that grades or gathers information from them. 

Output Devices

An output device is any peripheral that receives data from a computer, usually for display, projection, or physical reproduction. For example, the image shows an inkjet printer, an output device that can make a hard copy of any information shown on your monitor. Another example of an output device is a computer monitor, which displays an image that is received from the computer. Monitors and printers are two of the most common output devices used with a computer. 

Following are the common output devices.
  • Monitor 
  • Printer 
  • Speaker 
  • Headphone 
  • Projector 


A computer monitor, technically termed as a visual display unit, can be plainly described as an electronic device that transmits information from the computer onto a screen, thereby acting as an interface and connecting the viewer with the computer. At present, computer monitors are available in a variety of shapes, designs, and colors. However, based on the technology used to make computer monitors, they can be broadly categorized into three types.

1. CRT (Cathode Ray Tube)
2. LCD (Liquid Crystal Display) 
3. LED (Light-Emitting Diodes) 

1. CRT (Cathode Ray Tube) Monitors

These monitors employ the CRT technology used most commonly in the manufacturing of television screens. In this, a stream of intense high energy electrons is used to form images on a fluorescent screen. A cathode ray tube is a basically a vacuum tube containing an electron gun at one end and a fluorescent screen at another end. From this electron gun, a process called thermionic emission generates a strong beam of electrons. These electrons travel through a narrow path within the tube with high speed using various electro-magnetic devices and finally strike the phosphor points present on the fluorescent screen, thus creating an image. There are several advantages of using CRT monitors: 
  • These monitors are highly reliable and efficient, and are capable of generating a resolution of up to 2048 x 1536 pixels, thereby providing a clear picture quality. Also, CRT monitors that are now available are capable of producing thousands of different colors. 
  • Secondly, CRT monitors are affordable and cost effective. 
  • Unlike conventional CRT monitors, modern technological advancements have resulted in the development of flat screen CRT monitors that reduce the glare and are good for the eyes. However, the only concern with buying CRT monitors is that they are heavy and can occupy a great deal of work space. Also, these devices get heated up very easily. 
2.  LCD (Liquid Crystal Display) Monitors

Liquid crystal display, also known as liquid crystal diode, is one of the most advanced technologies available at present. Typically, an LCD monitor consists of a layer of color or monochrome pixels arranged schematically between a couple of transparent electrodes and two polarizing filters. Optical effect is achieved by polarizing the light in varied amounts and making it pass through the liquid crystal layer. At present, there are two types of LCD technology available. These include the active matrix or TFT and a passive matrix technology. Among these, TFT technology is more secure and reliable, and generates better picture quality. On the other hand, passive matrix has a slow response time and is slowly becoming outdated. In recent times, LCD monitors have become increasing popular with consumers. Some major advantages of using an LCD monitor include: 
  • These monitors are compact, lightweight, and do not consume much desk space. 
  • Secondly, these monitors do not consume much electricity and can even be operated by using batteries. 
  • Also, the images transmitted by these monitors do not get geometrically distorted and have little flicker. However, LCD monitors do have certain disadvantages. Most importantly, these monitors are very expensive. Secondly, image quality is not constant when viewed from different angles. Also, an LCD monitor’s resolution is always constant. Any alterations can result in a reduced performance. 
3. LED (Light-Emitting Diodes) Monitors

LED monitors are the latest types of monitors in the market today. Like LCD, it is again a flat panel display making use of light-emitting diodes for back-lightning instead of Cold Cathode Fluorescent (CCFL) back-lightning used in LCDs. Primarily, the display is of LCD only but the back-lightning is done by LEDs. LED monitors are said to use much lesser power than CRT and LCD. Thus, they are also considered environmental friendly. Other core advantages of LED monitors are: 
1. They produce images with higher contrast  
2. They have less negative environmental impact when disposed 
3. Lifespan and durability of LED monitors is more than CRT or LCD monitors 
4. Because of the technology, the monitor panels can be made very thin 
5. Do not produce much heat while running 


Organic LED (rather than silicon or germanium based like regular LEDs). Comparatively recent technology, so cost still quite variable and not available in really large sizes. In theory can be printed on plastic, resulting in lighter flexible displays with good brightness, good power consumption and good response time. 
LED monitors are little expensive than the former types. There are multiple ways by which LED back-lightning is done. 
  • White-edge LEDs are fixed around the rim of the monitor. It used a special diffusion panel to spread light evenly behind the screen. 
  • An array of LEDs are placed behind the screen. Their brightness is not controlled individually. 
  • Again an array of LEDs are placed behind the screen, but the brightness of each individual LED is controlled separately. 
Construct between Types of Monitors (LCD, LED and CRT)

LCD stands for Liquid Crystal Display which is a thin, flat display screen made up of any number of color or monochrome pixels arrayed in front of a light source or reflector.
LED stands for light emitting diode which is a semiconductor diode that emits incoherent narrow- spectrum of light when electrically biased in the Forward direction of the p-n junction. This effect is a form of electroluminescence.
CRT stands for cathode Ray Tube which is a tube coated with phosphorous in Inner surface. When electrons produced by e-gun come in Contact with phosphorous wall, light is produced by virtue of which we can see.
It is often used in electronic Devices because it uses very small amounts of electric power.
It can be used as a regular household light source.
It is generally used in TV screens, monitors, etc.


A printer is an electromechanical device which converts the text and graphical documents from electronic form to the physical form. Generally, they are the external peripheral devices which are connected with the computers or laptops through a cable or wirelessly to receive input data and print them on the papers. A wide range of printers are available with a variety of features ranging from printing black and white text documents to high quality colored graphic images. Quality of printers is identified by its features like color quality, speed of printing, resolution etc. Modern printers come with multipurpose functions i.e. they are combination of printer, scanner, photocopier, fax, etc. To serve different needs there are variety of printers available that works on different types of technologies. 

Difference between Impact & Non-Impact Printer

Dot matrix printer: A type of impact printer that produces characters and illustrations by striking pins against an ink ribbon to print closely spaced dots in the appropriate shape. Dot-matrix printers are relatively expensive and do not produce high-quality output. However, they can print to multi-page forms (that is, carbon copies), something laser and ink-jet printers cannot do. 


1. The Dot matrix printers are cheap and easily available in the market.  
2. They can make carbon copies of the print out unlike non-impact printers. 
3. The printing costs are the lowest as compared to other printers. 
4. The printout fades gradually rather than coming to a halt suddenly. You therefore get plenty of time 

Impact Printer

Non-Impact Printer
Text or image is formed in contact of paper and the printer head
Text or image is formed without any physical contact of the paper and the printer head
Noisy, slow and poor quality output.

Noiseless, fast and high quality Output
These printers are cheap.
Example – Dot matrix
These printers are expensive
Example –Laser and Ink-Jet

to change the ribbon before crisis emerges. 
5. They use paper continuously unlike other printers that require frequent change of paper.  
6. The maintenance cost is low as compared to other printers. 
7. They tolerate dirty and hot conditions as are found in industrial environments. 


1. The output is not high resolution. Color printout is limited and the print speed is also lesser as compared to non-impact printers. Therefore, the quality of print out in general is not very good. This affects the scanner readability of the print out. 
2. The printer creates great deal of noise while the pins strike the ribbon to the paper. 
3. The pins get bended easily destroying the print head. 
4. The single sheet of paper has to wound and aligned by hand which is time-consuming and hectic. This also makes it prone to jamming frequently. Although paper jamming can happen with any printer, fixing it here is not an easy task. 
5. The density of bar-codes is low and may fail to match user’s standards. 

Ink-jet printer

A type of printer that works by spraying ionized ink at a sheet of paper. Magnetized plates in the ink's path direct the ink onto the paper in the desired shapes. Inkjet printers are capable of producing high quality print approaching that produced by laser printers. A typical ink-jet printer provides a resolution of 600 dots per inch, although some newer models offer higher resolutions. 


1) Low cost 
2) High quality of output, capable of printing fine and smooth details 
3) Capable of printing in vivid color, good for printing pictures 
4) Easy to use 
5) Reasonably fast 
6) Quieter than dot matrix printer 
7) No warm up time 


1)  Print head is less durable, prone to clogging and damage 
2) Expensive replacement ink cartridges 
3) Not good for high volume printing 
4) Printing speed is not as fast as laser printers 
5) Ink bleeding, ink carried sideways causing blurred effects on some papers 
6) Aqueous ink is sensitive to water, even a small drop of water can cause blurring 

Laser Printer

A type of printer that utilizes a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work. 

1) Laser prints are generally very high and very accurate.  
2) For high volume printing laser printers are considerably cheaper to run. 
3) Printing is fast so they can cope large volumes.  
4) Due to the technology used prints from a laser printer emerge from the printer dry to the touch.

1) Buying a laser printer can be expensive when compared to an inkjet. 
2) Color laser printers are significantly more expensive than a color inkjet.  
3) Laser printers are larger and heavier as they need to comprise the imaging drum and laser technology. 


Speakers are one of the most common output devices used with computer systems. Some speakers are designed to work specifically with computers, while others can be hooked up to any type of sound system.  Regardless of their design, the purpose of speakers is to produce audio output that can be heard by the listener. Speakers are transducers that convert electromagnetic waves into sound waves. The speakers receive audio input from a device such as a computer or an audio receiver. This input may be either in analog or digital form. Analog speakers simply amplify the analog electromagnetic waves into sound waves. Since sound waves are produced in analog form, digital speakers must first convert the digital input to an analog signal, then generate the sound waves.  


Sometimes referred to as earphones, headphones are a hardware device that either plugs into your computer (line out) or your speakers to privately listen to audio without disturbing anyone else. The picture is an example of a USB headset from Logitech with a microphone and a popular solution for computer gaming.  Projector:  Often no larger than a toaster and only weighing a few pounds, a projector is an output device that can take images generated by a computer and reproduce them on a large, flat (usually lightly colored) surface. For example, projectors are used in meetings to help ensure that all participants can view the information being presented.  

Storage Devices

Storage Devices
Alternatively referred to as digital storage, storage, storage media, or storage medium, a storage device is any hardware capable of holding information either temporarily or permanently. There are two types of storage devices used with computers: a primary storage device, such as RAM, and a secondary storage device, like a hard drive. Secondary storage can be removable, internal, or external storage.  Storage devices are one of the core components of any computing device. They store virtually all the data and applications on a computer, except hardware firmware. They are available in different form factors depending on the type of underlying device. For example, a standard computer has multiple storage devices including RAM, cache, a hard disk, an optical disk drive and externally connected USB drives. 

There are two different types of storage devices
Primary Storage Devices: Generally smaller in size, are designed to hold data temporarily and are internal to the computer. They have the fastest data access speed, and include RAM and cache memory. 

Secondary Storage Devices: These usually have large storage capacity, and they store data permanently. They can be both internal and external to the computer, and they include the hard disk, compact disk drive and USB storage device. Let’s have a quick look on primary & secondary memory. 

Primary memory

Secondary memory
The memory devices used for primary memory are semiconductor memories
The primary memory is categorized as volatile and nonvolatile memories, RAM is the volatile memory and ROM is the nonvolatile memory
The primary memory is composed of programs and data that are presently being used by the  microprocessor

Primary memory is known as main memory

These memories are also called as internal memory
Primary memory is temporary
Commonly used primary memory (main memory) available in the range of 512 MB to 8 GB RAMs.
The primary memory devices are connected to the computer through “slots”
The secondary memory devices are magnetic and optical memories.
The secondary memory is always non volatile

The secondary memory is enough capable to store huge amount of information

The secondary memories are somewhat slow in interacting with the microprocessor, when compared with the primary memory  
Secondary memory is known as additional memory or back memory

The secondary memory is permanent Generally secondary memories range between 80 GB to 4 TB Hard Disc Drives.
The secondary memory devices are connected to the computer through Cables

List of Storage devices: 
  • RAM 
  • ROM 
  • Cache memory 
  • Hard disk 
  • CD 
  • DVD 
  • Floppy 
  • Pen drive 

Random Access Memory (RAM) is a hardware device that allows information to be stored and retrieved on a computer. RAM is usually associated with DRAM, which is a type of memory module. Because information is accessed randomly instead of sequentially like it is on a CD or hard drive, the computer can access the data much faster. However, unlike ROM or the hard drive, RAM is a volatile memory and requires power to keep the data accessible; if power is lost all data contained in memory lost. 

Short for Read-Only Memory, ROM is a storage medium that is used with computers and other electronic devices. As the name indicates, data stored in ROM may only be read; it is either modified with extreme difficulty or not at all. ROM is mostly used for firmware updates. A simple example of ROM is the cartridge used with video game consoles; which allows one system to run multiple games.
Differences between RAM and ROM RAM ( Random Access Memory)
ROM ( Read Only Memory)
Random Access Memory or RAM is a form of data storage that can be accessed randomly at any time, in any order and from any physical location., allowing quick access and manipulation

The full form of RAM is Random Access memory.

RAM allows the computer to read data quickly to run applications. It allows reading and writing.

RAM is volatile i.e. its contents are lost when the device is powered off
The two main types of RAM are static RAM and dynamic RAM.

Read-only memory or ROM is also a form of data storage that cannot be easily altered or reprogrammed. Stores instructions that are not necessary for re-booting up to make the computer operate when it is switched off. They are hardwired
The full form of ROM is Read Only memory.

ROM stores the program required to initially boot the computer. It only allows reading.

It is non-volatile i.e. its contents are retained even when the device is powered off.
The types of ROM include PROM, EPROM and EEPROM

Cache Memory

The basic purpose of cache memory is to store program instructions that are frequently re-referenced by software during operation. Fast access to these instructions increases the overall speed of the software program. 

Hard Disk

The primary computer storage medium, which is made of one or more aluminum or glass platters, coated with a ferromagnetic material. Although the terms "hard disk" and "hard drive" are used synonymously; technically, the disk spins inside the drive. All computers have an internal hard disk for storage, and hard disks in external cases can be plugged into a USB, Fire-wire or eSATA port for additional storage. Slowly but surely however, hard disks are being replaced by non-mechanical drives. Today, hard disks are "fixed disks," which means their platters reside permanently in the drive. In the past, before high-speed Internet connections were common, several types of removable disks were used for backup and transport. 

A compact disc is a poly-carbonate with one or more metal layers capable of storing digital information. The most prevalent types of compact discs are those used by the music industry to store digital recordings and CD-ROMs used to store computer data. Both of these types of compact disc are read-only, which means that once the data has been recorded onto them, they can only be read, or played.  

DVD (Digital Versatile Disc)

Stands for "Digital Versatile Disc." A DVD is a type of optical media used for storing digital data. It is the same size as a CD, but has a larger storage capacity. Some DVDs are formatted specifically for video playback, while others may contain different types of data, such as software programs and computer files. 

Blue Ray Disc 

Blue Ray DiscBlu-ray (not Blue-ray) also known as Blu-ray Disc (BD), is the name of a new optical disc format jointly developed by the Blu-ray Disc Association (BDA). A group of the world’s leading consumer electronics, personal computer and media manufacturers (including Apple, Dell, Hitachi, HP, JVC, LG, Mitsubishi, Panasonic, Pioneer, Philips, Samsung, Sharp, Sony, TDK and Thomson). The format was developed to enable recording, rewriting and playback of high-definition video (HD). The format offers more than five times the storage capacity of traditional DVDs and can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. 

 Floppy Disk

Floppy disks have an interesting name, considering they do not appear to be "floppy." However, if you take the actual disk out of the protective casing, you will discover that the disk is, in fact, rather flexible. It is coated with iron oxide and stores data magnetically, just like a hard disk.

Pen drive

B drive also known as a flash drive or key-chain drive is a plug-and-play portable storage device that uses flash memory and is lightweight enough to attach to a key-chain. A USB drive can be used in place of a floppy disk, Zip drive disk or CD. When the user plugs the device into the USB port, the computer's operating system recognizes the device as a removable drive and assigns it a drive letter.  


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What-If Analysis What-If Analysis in Excel allows you to try out different values (scenarios) for formulas. The following example helps you master what-if analysis quickly and easily.  Use scenarios to consider many different variables  A scenario is a set of values that Excel saves and can substitute automatically in cells on a worksheet. You can create and save different groups of values on a worksheet and then switch to any of these new scenarios to view different results. 
Create Different Scenarios 
Note: You can simply type in a different revenue and Cost into cell B2 and B3 respectively to see the corresponding result of a scenario in cell B4. However, what-if analysis enables you to easily compare the results of different scenarios.  
I. On the Data tab, click What-If Analysis and select Scenario Manager from the list. The Scenario Manager Dialog box appears  II. Add a scenario by clicking on Add.  III. Type a name (e.g. “First Case”), select cell B2 and B3 (represents “Revenue” and “…


Asking For and Giving Opinions on Likes and Dislikes

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Apology Etiquette and Office Vocabulary 

Chapter Vocabulary

Word Meaning Sample Sentence Stressed A state of any mental or emotional tension. Ram seems much stressed after his poor exam. Launch An act of instance of starting something. The government launched a new scheme for the poor people. Error A mistake Ravi found a grammatical error in his new grammar book. Scold Blaming someone for any wrong doing Bhuvan scolded his employees for their poor performance. Accuse Claiming that someone has done something wrong. Bharati accuses her friend Chaya for stealing her necklace. Fair Good and honest Ravi got promoted for doing a fair job. Ashamed Embarrassed or guilty because of one’s action. <