Year: 2020

Expansion Slots

An expansion slot is a socket on the motherboard that is used to insert an expansion card (or circuit board), which provides additional features to a computer such as video, sound, advanced graphics, Ethernet or memory.

The expansion card has an edge connector that fits precisely into the expansion slot as well as a row of contacts that is designed to establish an electrical connection between the motherboard and the electronics on the card, which are mostly integrated circuits. Depending on the form factor of the case and motherboard, a computer system generally can have anywhere from one to seven expansion slots. With a backplane system, up to 19 expansion cards can be installed.

Expansion cards can provide various functions including:

• Sound
• Modems
• Network
• Interface adapters
• TV and radio tuning
• Video processing
• Host adapting such as redundant array of independent disks or small computer system interface
• Solid-state drive
• Power-on self-test
• Advanced multirate codec
• Basic input/output system (BIOS)
• Expansion read-only memory (ROM)
• Security devices
• RAM memory

Older expansion cards also included memory expansion cards, clock/calendar cards, hard disk cards, compatibility cards for hardware emulation, and disk controller cards. The Altair 8800 was the first slot-type expansion card bus added to a microcomputer. It was developed in 1974-1975 by IBM Corp.

The expansion slot opening is generally located on the back of a PC and provides an electrical connection to the motherboard for an expansion card. Screws are then used to attach the card to the slot for added security.

(i) Video Controller

A video controller, often referred to as a video or graphics card, is a key hardware component that allows computers to generate graphic information to any video display devices, such as a monitor or projector. They are also known as graphics or video adapters. Some modern computers do not include video cards, but rather have graphics processing units directly integrated into the computer’s motherboard.

Older Video Controllers

A video controller, once more commonly referred to as a video display controller, were used in older models of home-computers during the 1980s; they were also used in some early video game system consoles. Their main function as an integrated circuit in a video signal generator was to produce television video signals in computers or game systems. Although they could generate graphics, older video controller models did not have specialized hardware accelerators that created 2D and 3D images.

Evolution of the Video Controller

Modern video controllers are installed with hardware accelerators that create both 2D and 3D images. They also offer various functions beyond accelerated image rendering, such as TV output and the ability to hook up to several monitors. Although many computers’ motherboards are already integrated with graphics processing units, you can disable the integrated graphics chip via the computer’s BIOS to install a higher-performance video controller via the accelerated graphics port. For a modern video controller to function properly in a computer, a computer needs to have four essential units: a functioning motherboard, a processor that generates the power that a video controller needs to perform its tasks, enough memory to distribute the images created by the GPU and a screen or monitor to properly display these images.

(ii) Sounds Cards

A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces used for professional audio applications.

Sound functionality can also be integrated onto the motherboard, using components similar to those found on plug-in cards. The integrated sound system is often still referred to as a sound card. Sound processing hardware is also present on modern video cards with HDMI to output sound along with the video using that connector; previously they used a S/PDIF connection to the motherboard or sound card.

Typical uses of sound cards or sound card functionality include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation, education and entertainment (games) and video projection. Sound cards are also used for computer-based communication such as voice over IP and teleconferencing.

The Small Computer System Interface (SCSI)

The Small Computer System Interface (SCSI) is a set of parallel interface standards developed by the American National Standards Institute (ANSI) for attaching printers, disk drives, scanners and other peripherals to computers. SCSI (pronounced “skuzzy”) is supported by all major operating systems.

SCSI Versions

The first version (SCSI-1), adopted by ANSI in 1986, was an 8-bit version with a 5 MBps transfer speed that allowed up to eight devices to be connected with a maximum cable length of six meters. The latest version, 16-bit Ultra-640 (Fast-320) SCSI, was introduced in 2003 and has a 640 MBps transfer speed, connecting up to 16 devices with a 12 meter cable length. Other versions include:

• SCSI-2: 8-bit bus, six meter cable length, 5-10 MBps; connects 8 or 16 devices. 50-pin connector.
• Wide SCSI-2: Received its name from the wider 168 line cable with 68-pin connectors to accommodate the 16-bit bus. 3 meter cable; 20 MBps transfer rate; connected 16 devices.
• Fast SCSI-2: 8-bit bus, but double the clock speed of SCSI-2 allowing transfers of 10-20 MBps. 3 meter cable; connects 8 devices.
• Fast Wide SCSI-2: 6-bit bus; 3 meter cable; 20 MBps; 16 devices.
• Ultra SCSI-3: 8-bit and 16-bit versions, both with 1.5 meter cable length. The 8-bit version supports data rates of 20 MBps and connects 8 devices. The 16-bit version doubled the transfer rate and number of devices.
• Ultra-2 SCSI: 8-bit bus; 12 meters; 40 MBps; 8 devices.
• Wide Ultra-2 SCSI: 16-bit bus; 12 meters; 80 MBps; 16 devices.

Traditional SCSI has been superseded by later attachment protocols such as Serial Attached SCSI (SAS) and iSCSI, which build on the earlier SCSI command structure.

Network Card

A Network interface card (also known as a NIC, network card, or network interface controller) is an electronic device that connects a computer to a computer network, usually a LAN. It is considered a piece of computer hardware. Most modern computers support an internal network interface controller embedded in the motherboard directly rather than provided as an external component.

Network cards let a computer exchange data with a network. To achieve the connection, network cards use a suitable protocol, for example CSMA/CD. Network cards usually implement the first two layers of the OSI model, that is the physical layer, and the data link layer. There are older network protocols such as ARCNET, introduced in 1977, LocalTalk or Token Ring, but today, most network cards use Ethernet.

Ethernet cards are available in several different standard packages called form factors that have evolved over the last several generations of PC hardware:

• In the 1990s and early 2000s, large Industry Standard Architecture cards were the first standard for PCs. Computer owners had to open the computer’s case to install the card.
• Newer Ethernet cards installed inside desktop computers use the Peripheral Component Interconnect standard and are usually installed by the manufacturer. These cards are still common in desktop PCs, for computers whose motherboards do not contain an onboard Ethernet port.
• Smaller Personal Computer Memory Card International Association Ethernet cards that resemble credit cards are readily available for laptop and other mobile computers. These insert conveniently into slots on the side or front of the device. The PC Card is a common PCMCIA device, although only certain PC Card and PCMCIA products support Ethernet. By the early 2010s, however, fewer laptops supported the PCMCIA standard.
• Though they look more like small boxes than cards, external USB Ethernet adapters also fill a market niche. These devices are a convenient alternative to PCI cards for desktop computers and they’re also commonly used with video game consoles and other consumer devices lacking PCMCIA slots and devices.

Input device enables the user to send data, information, or control signals to a computer. The Central Processing Unit (CPU) of a computer receives the input and processes it to produce the output.

Input Devices are:

• Keyboard
• Mouse
• Light Pen
• Touch Screen
• Scanner
• Joystick
• Microphone
• Magnetic Ink Character Recognition (MICR)
• Optical Character Reader (OCR)

1. Keyboard

The keyboard is a basic input device that is used to enter data into a computer or any other electronic device by pressing keys. It has different sets of keys for letters, numbers, characters, and functions. Keyboards are connected to a computer through USB or a Bluetooth device for wireless communication.

Types of keyboards: There can be different types of keyboards based on the region and language used. Some of the common types of keyboards are as follows:

(i) QWERTY Keyboard

It is the most commonly used keyboard with computers in modern times. It is named after the first six letters of the top row of buttons and is even popular in countries that do not use Latin-based alphabet. It is so popular that some people think that it is the only type of keyboard to use with computers as an input device.

(ii) AZERTY Keyboard

It is considered the standard French keyboard. It is developed in France as an alternative layout to the QWERTY layout and is mainly used in France and other European countries. Some countries have manufactured their own versions of AZERTY.

Its name is derived from the first six letters that appear on the top left row of the keyboard. The Q and W keys in AZERTY keyboard are interchanged with A and Z keys in QWERTY keyboard. Furthermore, in AZERTY keyboard M key is located to the left of the L key.

AZERTY keyboard differs from QWERTY keyboard not only in the placement of letters but also in many other ways, e.g., it gives emphasis on accents, which is required for writing European languages like French.

(iii) DVORAK Keyboard

This type of keyboard layout was developed to increase the typing speed by reducing the finger movement while typing. The most frequently used letters are kept in a home row to improve typing.

2. Mouse

The mouse is a hand-held input device which is used to move cursor or pointer across the screen. It is designed to be used on a flat surface and generally has left and right button and a scroll wheel between them. Laptop computers come with a touchpad that works as a mouse. It lets you control the movement of cursor or pointer by moving your finger over the touchpad. Some mouse comes with integrated features such as extra buttons to perform different buttons.

The mouse was invented by Douglas C. Engelbart in 1963. Early mouse had a roller ball integrated as a movement sensor underneath the device. Modern mouse devices come with optical technology that controls cursor movements by a visible or invisible light beam. A mouse is connected to a computer through different ports depending on the type of computer and type of a mouse.

Common types of the mouse:-

(i) Trackball Mouse

It is a stationary input device that has ball mechanism to move the pointer or cursor on the screen. The ball is half inserted in the device and can be easily rolled with finger, thumb or the palm to move the pointer on the screen. The device has sensor to detect the rotation of ball. It remains stationary; you don’t need to move it on the operating surface. So, it is an ideal device if you have limited desk space as you don’t need to move it like a mouse.

(ii) Mechanical Mouse

It has a system of a ball and several rollers to track its movement. It is a corded type of mouse. A mechanical mouse can be used for high performance. The drawback is that they tend to get dust into the mechanics and thus require regular cleaning.

(iii) Optical Mouse

An optical mouse uses optical electronics to track its movement. It is more reliable than a mechanical mouse and also requires less maintenance. However, its performance is affected by the surface on which it is operated. Plain non-glossy mouse mat should be used for best results. The rough surface may cause problems for the optical recognition system, and the glossy surface may reflect the light wrongly and thus may cause tracking issues.

(iv) Cordless or Wireless Mouse

As the name suggests, this type of mouse lacks cable and uses wireless technology such as IrDA (infrared) or radio (Bluetooth or Wi-Fi) to control the movement of the cursor. It is used to improve the experience of using a mouse. It uses batteries for its power supply.

3. Light Pen

A light pen is a computer input device that looks like a pen. The tip of the light pen contains a light-sensitive detector that enables the user to point to or select objects on the display screen. Its light sensitive tip detects the object location and sends the corresponding signals to the CPU. It is not compatible with LCD screens, so it is not in use today. It also helps you draw on the screen if needed. The first light pen was invented around 1955 as a part of the Whirlwind project at the Massachusetts Institute of Technology (MIT).

4. Touch Screen

A touch screen is a computer display screen that serves as an input device. When a touch screen is touched by a finger or stylus, it registers the event and sends it to a controller for processing.

A touch screen may contain pictures or words that the user can touch to interact with the device.

• Scanner
• Magnetic Ink Character Recognition (MICR)
• Optical Character Reader (OCR)
• Optical mark recognition (OMR)

1. Scanner

The scanner uses the pictures and pages of text as input. It scans the picture or a document. The scanned picture or document then converted into a digital format or file and is displayed on the screen as an output. It uses optical character recognition techniques to convert images into digital ones. Some of the common types of scanners are as follows:

Types of Scanner:

(i) Flatbed Scanner

It has a glass pane and a moving optical CIS or CCD array. The light illuminates the pane, and then the image is placed on the glass pane. The light moves across the glass pane and scans the document and thus produces its digital copy. You will need a transparency adapter while scanning transparent slides.

(ii) Handheld Scanner

It is a small manual scanning device which is held by hand and is rolled over a flat image that is to be scanned. The drawback in using this device is that the hand should be steady while scanning; otherwise, it may distort the image. One of the commonly used handheld scanners is the barcode scanner which you would have seen in shopping stores.

(iii) Sheetfed Scanner

In this scanner, the document is inserted into the slot provided in the scanner. The main components of this scanner include the sheet-feeder, scanning module, and calibration sheet. The light does not move in this scanner. Instead, the document moves through the scanner. It is suitable for scanning single page documents, not for thick objects like books, magazines, etc.

(iv) Drum Scanner

Drum scanner has a photomultiplier tube (PMT) to scan images. It does not have a charge-coupled device like a flatbed scanner. The photomultiplier tube is extremely sensitive to light. The image is placed on a glass tube, and the light moves across the image, which produces a reflection of the image which is captured by the PMT and processed. These scanners have high resolution and are suitable for detailed scans.

(v) Photo Scanner

It is designed to scan photographs. It has high resolution and color depth, which are required for scanning photographs. Some photo scanners come with in-built software for cleaning and restoring old photographs.

2. Magnetic Ink Character Recognition (MICR)

MICR computer input device is designed to read the text printed with magnetic ink. MICR is a character recognition technology that makes use of special magnetized ink which is sensitive to magnetic fields. It is widely used in banks to process the cheques and other organizations where security is a major concern. It can process three hundred cheques in a minute with hundred-percent accuracy. The details on the bottom of the cheque (MICR No.) are written with magnetic ink. A laser printer with MICR toner can be used to print the magnetic ink.

The device reads the details and sends to a computer for processing. A document printed in magnetic ink is required to pass through a machine which magnetizes the ink, and the magnetic information is then translated into characters.

3. Optical Character Reader (OCR)

OCR computer input device is designed to convert the scanned images of handwritten, typed or printed text into digital text. It is widely used in offices and libraries to convert documents and books into electronic files.

It processes and copies the physical form of a document using a scanner. After copying the documents, the OCR software converts the documents into a two-color (black and white), version called bitmap. Then it is analyzed for light and dark areas, where the dark areas are selected as characters, and the light area is identified as background. It is widely used to convert hard copy legal or historic documents into PDFs. The converted documents can be edited if required like we edit documents created in ms word.

4. Optical mark recognition (OMR)

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 a piece of paper.

OMR allows for the processing of hundreds or thousands of documents per hour. For example, students may recall taking tests or surveys where they filled in bubbles on paper (shown right) with a 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.

An output device is any device used to send data from a computer to another device or user. Most computer data output that is meant for humans is in the form of audio or video. Thus, most output devices used by humans are in these categories. Examples include monitors, projectors, speakers, headphones and printers.

Following are some of the important output devices used in a computer.

• Monitors
• Graphic Plotter
• Printer

Monitors

Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.

There are two kinds of viewing screen used for monitors.

• Cathode-Ray Tube (CRT)
• Flat-Panel Display

(i) Cathode-Ray Tube (CRT) Monitor

The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity or resolution. It takes more than one illuminated pixel to form a whole character, such as the letter ‘e’ in the word help.

A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes – fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.

There are some disadvantages of CRT

• Large in Size
• High power consumption

(ii) Flat-Panel Display Monitor

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, and graphics display.

The flat-panel display is divided into two categories −

• Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes).
• Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device).

Printer

A printer is an external hardware output device that takes the electronic data stored on a computer or other device and generates a hard copy of it. For example, if you created a report on your computer, you could print several copies to hand out at a staff meeting. Printers are one of the most popular computer peripherals and are commonly used to print text and photos. The picture to the right is an example of an inkjet computer printer, the Lexmark Z605.

There are two types of printers:

• Impact Printers
• Non-Impact Printers

1. Impact Printers

Impact printers print the characters by striking them on the ribbon, which is then pressed on the paper.

Characteristics of Impact Printers are the following −

• Very low consumable costs
• Very noisy
• Useful for bulk printing due to low cost
• There is physical contact with the paper to produce an image

These printers are of two types −

(i) Character printers

(ii) Line printers

Character Printers

Character printers are the printers which print one character at a time.

These are further divided into two types:

(i) Dot Matrix Printer(DMP)

(ii) Daisy Wheel

Dot Matrix Printer

In the market, one of the most popular printers is Dot Matrix Printer. These printers are popular because of their ease of printing and economical price. Each character printed is in the form of pattern of dots and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to form a character which is why it is called Dot Matrix Printer.

Advantages

• Inexpensive
• Widely Used
• Other language characters can be printed

Disadvantages

• Slow Speed
• Poor Quality

Daisy Wheel

Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower) which is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices that require a few letters to be sent here and there with very nice quality.

Advantages

• More reliable than DMP
• Better quality
• Fonts of character can be easily changed

Disadvantages

• Slower than DMP
• Noisy
• More expensive than DMP

Line Printers

Line printers are the printers which print one line at a time.

These are of two types −

(i) Drum Printer

(ii) Chain Printer

Drum Printer

This printer is like a drum in shape hence it is called drum printer. The surface of the drum is divided into a number of tracks. Total tracks are equal to the size of the paper, i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track. Different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can print 300 to 2000 lines per minute.

Advantages

• Very high speed

Disadvantages

• Very expensive
• Characters fonts cannot be changed

Chain Printer

In this printer, a chain of character sets is used, hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters.

Advantages

• Character fonts can easily be changed.
• Different languages can be used with the same printer.

Disadvantages

• Noisy

2. Non-impact Printers

Non-impact printers print the characters without using the ribbon. These printers print a complete page at a time, thus they are also called as Page Printers.

These printers are of two types −

(i) Laser Printers

(ii) Inkjet Printers

Characteristics of Non-impact Printers

• Faster than impact printers
• They are not noisy
• High quality
• Supports many fonts and different character size

Laser Printers

These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.

Advantages

• Very high speed
• Very high quality output
• Good graphics quality
• Supports many fonts and different character size

Disadvantages

• Expensive
• Cannot be used to produce multiple copies of a document in a single printing

Inkjet Printers

Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features.

They make less noise because no hammering is done and these have many styles of printing modes available. Color printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.

Advantages

• High quality printing
• More reliable

Disadvantages

• Expensive as the cost per page is high
• Slow as compared to laser printer

3. Plotter

A plotter is a computer hardware device much like a printer that is used for printing vector graphics. Instead of toner, plotters use a pen, pencil, marker, or another writing tool to draw multiple, continuous lines onto paper rather than a series of dots like a traditional printer. Though once widely used for computer-aided design, these devices have more or less been phased out by wide-format printers. Plotters are used to produce a hard copy of schematics and other similar applications.

Advantages of plotters

• Plotters can work on very large sheets of paper while maintaining high resolution.
• They can print on a wide variety of flat materials including plywood, aluminum, sheet steel, cardboard, and plastic.
• Plotters allow the same pattern to be drawn thousands of times without any image degradation.

Disadvantages of plotters

• Plotters are quite large when compared to a traditional printer.
• Plotters are also much more expensive than a traditional printer.

A diskette drive is a term used to describe a floppy disk drive. Commonly the A: or B: drive on IBM compatible computers; this drive allows users to read and write information to floppy disk drives.

A diskette is a random access, removable data storage medium that can be used with personal computers. The term usually refers to the magnetic medium housed in a rigid plastic cartridge measuring 3.5 inches square and about 2millimeters thick. Also called a “3.5-inch diskette,” it can store up to 1.44 megabytes (MB) of data. Although many personal computers today come with a 3.5-inch diskette drive pre-installed, some notebook computers and centrally-administered desktop computers omit them.

Some older computers provide drives for magnetic diskettes that are 5.25 inches square, about 1 millimeter thick, and capable of holding 1.2 megabytes of data. These were sometimes called “floppy disks” or “floppies” because their housings are flexible. In recent years, 5.25-inch diskettes have been largely replaced by 3.5-inch diskettes, which are physically more rugged. Many people also call the newer hard-cased diskette a “floppy.”

Magnetic diskettes are convenient for storing individual files and small programs. However, the magneto-optical (MO) disk is more popular for mass storage, backup, and archiving. An MO diskette is only a little larger, physically, than a conventional 3.5-inch magnetic diskette. But because of the sophisticated read/write technology, the MO diskette can store many times more data.

Types of Diskettes

There are dozens of types of diskettes commercially available. If one were to cite a single properly, however, that most distinguishes one of these products from another, that property would likely be size.

Diskettes are widely available in three sizes (diameters)- 3.5 inches, 5.25 inches, and 8 inches. Historically, the 8-inch diskettes came along first, then respectively, their 5.25 inch and 3.5 inch counterparts.

The 8 inch and 5.25 inch diskettes are encased in flexible, plastic-coated cardboard jack­ets, whereas the 3.5 inch diskettes are contained in rugged plastic cases that can fit into a shirt pocket.

Eight-inch diskettes are more commonly used with small minicomputers and 5.25 inch and 3.5 inch sizes with micro­computer systems. Strange as it may seem, 3.5 inch diskettes can store more data than 5.25 inch ones.

Despite their small size, diskettes can store a respectable amount of data. Common capacities are 360 kilobytes for 5.25 inch diskettes and 720 kilo­bytes, 800 kilobytes, or 1.44 megabytes for 3.5 inch diskettes.

A 360 kilo­byte diskette can store over 100 typewritten pages of information; thus, 3.5 inch diskettes can store about 400 pages. Mega floppies- diskettes that can carry 2, 4, or 10 megabytes of data- are also available, although not com­monly found in practice.

It is highly possible that the next generation of microcomputers will use a mega floppy format.

To protect data, diskettes also contain a write-protect notch or square. This prevents the user from accidentally writing on the disk. Covering the notch on 5.25 inch diskettes makes it impossible to write on the surface.

The convention on 3.5 inch and 8 inch diskettes is the opposite: Exposing the notch or square makes writing impossible.

Disk Density

Disk density is a capacity designation on magnetic storage, usually floppy disks. Each designation describes a set of characteristics that can affect the areal density of a disk or the efficiency of the encoded data. Such characteristics include modulation method, track width, coercivity, and magnetic field direction.

High Density Disk

A high-quality floppy disk capable of holding more data than a double-density disk. High-density 5¼-inch disks for PCs can hold 1.2-MB (megabytes) of data. High-density 3½-inch disks can store 1.44MB.

Formatting Boot Record FAT Folder Directory

A FAT file system is a specific type of computer file system architecture and a family of industry-standard file systems utilizing it.

The FAT file system is a legacy file system which is simple and robust. It offers good performance even in very light-weight implementations, but cannot deliver the same performance, reliability and scalability as some modern file systems. It is, however, supported for compatibility reasons by nearly all currently developed operating systems for personal computers and many home computers, mobile devices and embedded systems, and thus is a well suited format for data exchange between computers and devices of almost any type and age from 1981 through the present.

Originally designed in 1977 for use on floppy disks, FAT was soon adapted and used almost universally on hard disks throughout the DOS and Windows 9x eras for two decades. Today, FAT file systems are still commonly found on floppy disks, USB sticks, flash and other solid-state memory cards and modules, and many portable and embedded devices. DCF implements FAT as the standard file system for digital cameras since 1998. FAT is also utilized for the EFI system partition (partition type 0xEF) in the boot stage of EFI-compliant computers.

For floppy disks, FAT has been standardized as ECMA-107 and ISO/IEC 9293:1994 (superseding ISO 9293:1987). These standards cover FAT12 and FAT16 with only short 8.3 filename support; long filenames with VFAT are partially patented. According to Google Patents the “Common name space for long and short filenames”(US5758352A) status was expired in 2019, which may mean that patents expired completely.

Hard Disk Drive

A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that uses magnetic storage to store and retrieve digital data using one or more rigid rapidly rotating platters coated with magnetic material. The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a random-access manner, meaning that individual blocks of data can be stored and retrieved in any order. HDDs are a type of non-volatile storage, retaining stored data even when powered off.

Introduced by IBM in 1956, HDDs were the dominant secondary storage device for general-purpose computers beginning in the early 1960s. HDDs maintained this position into the modern era of servers and personal computers, though personal computing devices produced in large volume, like cell phones and tablets, rely on flash products. More than 224 companies have produced HDDs historically, though after extensive industry consolidation most units are manufactured by Seagate, Toshiba, and Western Digital. HDDs dominate the volume of storage produced (exabytes per year) for servers. Though production is growing slowly, sales revenues and unit shipments are declining because solid-state drives (SSDs) have higher data-transfer rates, higher areal storage density, better reliability, and much lower latency and access times.

The revenues for SSDs, most of which use NAND, slightly exceed those for HDDs. Flash storage products had more than twice the revenue of hard disk drives as of 2017. Though SSDs have four to nine times higher cost per bit, they are replacing HDDs in applications where speed, power consumption, small size, high capacity and durability are important. Cost per bit for SSDs is falling, and the price premium over HDDs has narrowed.

The primary characteristics of an HDD are its capacity and performance. Capacity is specified in unit prefixes corresponding to powers of 1000: a 1-terabyte (TB) drive has a capacity of 1,000 gigabytes (GB; where 1 gigabyte = 1 billion bytes). Typically, some of an HDD’s capacity is unavailable to the user because it is used by the file system and the computer operating system, and possibly inbuilt redundancy for error correction and recovery. Also there is confusion regarding storage capacity, since capacities are stated in decimal Gigabytes (powers of 10) by HDD manufacturers, whereas some operating systems report capacities in binary Gibibytes, which results in a smaller number than advertised. Performance is specified by the time required to move the heads to a track or cylinder (average access time) adding the time it takes for the desired sector to move under the head (average latency, which is a function of the physical rotational speed in revolutions per minute), and finally the speed at which the data is transmitted (data rate).

The two most common form factors for modern HDDs are 3.5-inch, for desktop computers, and 2.5-inch, primarily for laptops. HDDs are connected to systems by standard interface cables such as PATA (Parallel ATA), SATA (Serial ATA), USB or SAS (Serial Attached SCSI) cables.

CD Rom Drive

A CD-ROM (compact disc read-only memory) is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of read-only memory.

During the 1990s, CD-ROMs were popularly used to distribute software and data for computers and fourth generation video game consoles. Some CDs, called enhanced CDs, hold both computer data and audio with the latter capable of being played on a CD player, while data (such as software or digital video) is only usable on a computer (such as ISO 9660 format PC CD-ROMs).

The CD-ROM format was developed by Japanese company Denon in 1982. It was an extension of Compact Disc Digital Audio, and adapted the format to hold any form of digital data, with a storage capacity of 553 MB. CD-ROM was then introduced by Denon and Sony at a Japanese computer show in 1984. The Yellow Book is the technical standard that defines the format of CD-ROMs. One of a set of color-bound books that contain the technical specifications for all CD formats, the Yellow Book, standardized by Sony and Philips in 1983, specifies a format for discs with a maximum capacity of 650 MB.

DVD Rom Drive

Digital versatile disc-read only memory (DVD-ROM) is a read-only digital versatile disc (DVD) commonly used for storing large software applications. It is similar to a compact disk-read only memory (CD-ROM) but has a larger capacity. A DVD-ROM stores around 4.38 GB of data. A CD-ROM usually stores 650 MB of data.

A DVD-ROM permanently stores data files which cannot be changed, written over or erased. A personal computer (PC) with a DVD-ROM or a DVD-RAM drive is designed to read a DVD-ROM disc. Generally a DVD-ROM disc is not equipped to be used with a DVD drive connected to a home theater system or television. But many DVD-ROM drives can generally read a DVD movie disc.

A DVD-ROM is one of the various types of DVDs. A blank DVD is generally a DVD-R or DVD+R, which has a read-write format. The +R or -R references the format standards and is a rewritable or recordable DVD.

Compared to a CD-ROM, a DVD-ROM has the same 5 inch diameter and 1.2 millimeter (mm) thickness. But because a DVD-ROM uses a shorter wavelength laser with tighter compacted pits, the disc capacity is increased. In fact, the smallest DVD-ROM can store approximately 7 times more data than a CD-ROM.

Tape Drive

A tape drive is a data storage device that reads and writes data on a magnetic tape. Magnetic tape data storage is typically used for offline, archival data storage. Tape media generally has a favorable unit cost and a long archival stability.

A tape drive provides sequential access storage, unlike a hard disk drive, which provides direct access storage. A disk drive can move to any position on the disk in a few milliseconds, but a tape drive must physically wind tape between reels to read any one particular piece of data. As a result, tape drives have very large average access times. However, tape drives can stream data very quickly off a tape when the required position has been reached. For example, as of 2010 Linear Tape-Open (LTO) supported continuous data transfer rates of up to 140 MB/s, a rate comparable to hard disk drives.

Software is a collection of instructions that enable the user to interact with a computer, its hardware, or perform tasks. Without software, most computers would be useless. For example, without your Internet browser software, you could not surf the Internet or read this page. Without an operating system, the browser could not run on your computer. The picture shows a Microsoft Excel box, an example of a spreadsheet software program.

Computer software, or simply software, is a collection of data or computer instructions that tell the computer how to work. This is in contrast to physical hardware, from which the system is built and actually performs the work. In computer science and software engineering, computer software is all information processed by computer systems, programs and data. Computer software includes computer programs, libraries and related non-executable data, such as online documentation or digital media. Computer hardware and software require each other and neither can be realistically used on its own.

The majority of software is written in high-level programming languages. They are easier and more efficient for programmers because they are closer to natural languages than machine languages. High-level languages are translated into machine language using a compiler or an interpreter or a combination of the two. Software may also be written in a low-level assembly language, which has strong correspondence to the computer’s machine language instructions and is translated into machine language using an assembler.

Introduction to Programming Languages

A programming language is a formal language, which comprises a set of instructions that produce various kinds of output. Programming languages are used in computer programming to implement algorithms.

Most programming languages consist of instructions for computers. There are programmable machines that use a set of specific instructions, rather than general programming languages. Early ones preceded the invention of the digital computer, the first probably being the automatic flute player described in the 9th century by the brothers Musa in Baghdad, during the Islamic Golden Age. Since the early 1800s, programs have been used to direct the behavior of machines such as Jacquard looms, music boxes and player pianos. The programs for these machines (such as a player piano’s scrolls) did not produce different behavior in response to different inputs or conditions.

Thousands of different programming languages have been created, and more are being created every year. Many programming languages are written in an imperative form (i.e., as a sequence of operations to perform) while other languages use the declarative form (i.e. the desired result is specified, not how to achieve it).

The description of a programming language is usually split into the two components of syntax (form) and semantics (meaning). Some languages are defined by a specification document (for example, the C programming language is specified by an ISO Standard) while other languages (such as Perl) have a dominant implementation that is treated as a reference. Some languages have both, with the basic language defined by a standard and extensions taken from the dominant implementation being common.

System Software

System software is software designed to provide a platform for other software. Examples of system software include operating systems like macOS, GNU/Linux and Microsoft Windows, computational science software, game engines, industrial automation, and software as a service applications.

In contrast to system software, software that allows users to do user-oriented tasks such as create text documents, play games, listen to music, or browse the web are collectively referred to as application software.

In the early days of computing most application software was custom-written by computer users to fit their specific hardware and requirements. In contrast, system software was usually supplied by the manufacturer of the computer hardware and was intended to be used by most or all users of that system.

The line where the distinction should be drawn is not always clear. Many operating systems bundle application software. Such software is not considered system software when it can be uninstalled usually without affecting the functioning of other software. Exceptions could be e.g. web browsers such as Internet Explorer where Microsoft argued in court that it was system software that could not be uninstalled. Later examples are Chrome OS and Firefox OS where the browser functions as the only user interface and the only way to run programs (and other web browsers can not be installed in their place), then they can well be argued to be the operating system and hence system software.

Another borderline example is cloud-based software. This software provides services to a software client (usually a web browser or a JavaScript application running in the web browser), not to the user directly, and is therefore systems software. It is also developed using system programming methodologies and systems programming languages. Yet from the perspective of functionality there is little difference between a word processing application and word processing web application.

Operating System Utilities

We have seen that the fundamental purpose of the operating system is to manage the various system resources. We have also examined the human computer interface which allows us to interact with the operating system. There is, however, a significant body of software that, while not strictly part of the operating system itself, cannot be described as application software. This software is often bundled with the operating system software, and comes under the general heading of utility software.

Utility software can include file re-organization utilities, backup programs, and a whole range of communication services. Many of the utilities that are bundled with a particular operating system are installed by default, although a significant number are optional and must be explicitly selected for installation.

The number and type of utility program provided varies from one operating system to another, but common examples include facilities to partition and format hard drives and floppy disks, file encryption and compression utilities, and task scheduling programs. These utilities are often implemented as stand-alone programs and can be run by the user in much the same way as an application program. In many cases, there are a number of proprietary utility programs on the market that carry out the same tasks, but with additional value added features.

Utility Software

Utility software is software designed to help to analyze, configure, optimize or maintain a computer. It is used to support the computer infrastructure – in contrast to application software, which is aimed at directly performing tasks that benefit ordinary users. However, utilities often form part of application systems. For example a batch job may run user-written code to update a database and may then include a step that runs a utility to back up the database, or a job may run a utility to compress a disk before copying files.

Although a basic set of utility programs is usually distributed with an operating system (OS), and this first party utility software is often considered part of the operating system, users often install replacements or additional utilities. Those utilities may provide additional facilities to carry out tasks that are beyond the capabilities of the operating system.

Many utilities that might affect the entire computer system require the user to have elevated privileges, while others that operate only on the user’s data do not.

Application software is a program or group of programs designed for end users. These programs are divided into two classes: system software and application software. While system software consists of low-level programs that interact with computers at a basic level, application software resides above system software and includes applications such as database programs, word processors and spreadsheets. Application software may be bundled with system software or published alone.

Application software may simply be referred to as an application.

Different types of application software include:

1. Application Suite

Has multiple applications bundled together. Related functions, features and user interfaces interact with each other.

2. Enterprise Software

Addresses an organization’s needs and data flow in a huge distributed environment.

3. Enterprise Infrastructure Software

Provides capabilities required to support enterprise software systems.

4. Information Worker Software

Addresses individual needs required to manage and create information for individual projects within departments.

5. Content Access Software

Used to access content and addresses a desire for published digital content and entertainment.

6. Educational Software

Provides content intended for use by students.

7. Media Development Software

Addresses individual needs to generate and print electronic media for others to consume.

Word Processor

A word processor is software or a device that allows users to create, edit, and print documents. It enables you to write text, store it electronically, display it on a screen, modify it by entering commands and characters from the keyboard, and print it.

Of all computer applications, word processing is the most common. Today, most word processors are delivered either as a cloud service or as software that users can install on a PC or mobile device.

Standard Features of Word Processors

Word processors vary considerably, but all word processors, whether cloud-based or installed on a system, support the following basic features:

(i) Insert text: Allows you to insert text anywhere in the document.

(ii) Delete text: Allows you to erase characters, words, lines, or pages.

(iii) Cut and Paste: Allows you to remove (cut) a section of text from one place in a document and insert (paste) it somewhere else.

(iv) Copy: Allows you to duplicate a section of text.

(v) Page Size and Margins: Allows you to define various page sizes and margins, and the word processor will automatically readjust the text so that it fits.

(vi) Search and Replace: Allows you to direct the word processor to search for a particular word or phrase. You can also direct the word processor to replace one group of characters with another everywhere that the first group appears.

(vii) Word Wrap: Automatically moves to the next line when you have filled one line with text, and it will readjust text if you change the margins.

(viii) Print: Allows you to send a document to a printer to get hard copy.

(ix) File management: Provides file management capabilities that allow you to create, delete, move, and search for files.

(x) Font Specifications: Allows you to change fonts within a document. For example, you can specify bold, italics, and underlining. Most word processors also let you change the font size and even the typeface.

(xi) Windows: Allows you to edit two or more documents at the same time. Each document appears in a separate window. This is particularly valuable when working on a large project that consists of several different files.

(xii) Spell Checking: Identifies words that don’t appear in a standard dictionary.

Spreadsheet

A spreadsheet or worksheet is a file made of rows and columns that help sort data, arrange data easily, and calculate numerical data. What makes a spreadsheet software program unique is its ability to calculate values using mathematical formulas and the data in cells. A good example of how a spreadsheet may be utilized is creating an overview of your bank’s balance.

A spreadsheet is a computer application for organization, analysis and storage of data in tabular form. Spreadsheets were developed as computerized analogs of paper accounting worksheets. The program operates on data entered in cells of a table. Each cell may contain either numeric or text data, or the results of formulas that automatically calculate and display a value based on the contents of other cells. A spreadsheet may also refer to one such electronic document.

Spreadsheet users can adjust any stored value and observe the effects on calculated values. This makes the spreadsheet useful for “what-if” analysis since many cases can be rapidly investigated without manual recalculation. Modern spreadsheet software can have multiple interacting sheets, and can display data either as text and numerals, or in graphical form.

Besides performing basic arithmetic and mathematical functions, modern spreadsheets provide built-in functions for common financial and statistical operations. Such calculations as net present value or standard deviation can be applied to tabular data with a pre-programmed function in a formula. Spreadsheet programs also provide conditional expressions, functions to convert between text and numbers, and functions that operate on strings of text.

Spreadsheets have replaced paper-based systems throughout the business world. Although they were first developed for accounting or bookkeeping tasks, they now are used extensively in any context where tabular lists are built, sorted, and shared.

LANPAR, available in 1969, was the first electronic spreadsheet on mainframe and time sharing computers. LANPAR was an acronym: LANguage for Programming Arrays at Random. VisiCalc was the first electronic spreadsheet on a microcomputer, and it helped turn the Apple II computer into a popular and widely used system. Lotus 1-2-3 was the leading spreadsheet when DOS was the dominant operating system. Excel now has the largest market share on the Windows and Macintosh platforms. A spreadsheet program is a standard feature of an office productivity suite; since the advent of web apps, office suites now also exist in web app form. Web based spreadsheets are a relatively new category.

DBMS

A database management system (DBMS) is a software package designed to define, manipulate, retrieve and manage data in a database. A DBMS generally manipulates the data itself, the data format, field names, record structure and file structure. It also defines rules to validate and manipulate this data.

A DBMS relieves users of framing programs for data maintenance. Fourth-generation query languages, such as SQL, are used along with the DBMS package to interact with a database.

Some other DBMS examples include:

• MySQL
• SQL Server
• Oracle
• dBASE
• FoxPro

A database management system receives instruction from a database administrator (DBA) and accordingly instructs the system to make the necessary changes. These commands can be to load, retrieve or modify existing data from the system.

A DBMS always provides data independence. Any change in storage mechanism and formats are performed without modifying the entire application. There are four main types of database organization:

(i) Relational Database

Data is organized as logically independent tables. Relationships among tables are shown through shared data. The data in one table may reference similar data in other tables, which maintains the integrity of the links among them. This feature is referred to as referential integrity – an important concept in a relational database system. Operations such as “select” and “join” can be performed on these tables. This is the most widely used system of database organization.

(ii) Flat Database

Data is organized in a single kind of record with a fixed number of fields. This database type encounters more errors due to the repetitive nature of data.

(iii) Object-Oriented Database

Data is organized with similarity to object-oriented programming concepts. An object consists of data and methods, while classes group objects having similar data and methods.

(iv) Hierarchical Database

Data is organized with hierarchical relationships. It becomes a complex network if the one-to-many relationship is violated.

Presentation Graphics

Presentation graphics is any graphic used during a presentation in place of data. A good example is a graphic of a chart, rather than the actual data it represents.

Business graphics, charts and diagrams used in a presentation. Presentation graphics software provides predefined backgrounds and sample page layouts to assist in the creation of computer-driven slide shows, which, in combination with a data projector, made the 35mm slide presentation obsolete. Navigation from page to page (slide to slide) can be done manually or automatically every so many seconds. The most popular presentation software is Microsoft PowerPoint (see PowerPoint). Frames and Transitions The format is a series of horizontal frames (slides) with transitions between them. Images, text, audio and video are laid out on the frames, and speaker’s notes can be added. Like any page layout program, elements on a frame can be moved around and resized.

Web Browser

 A web browser (commonly referred to as a browser) is a software application for accessing information on the World Wide Web. When a user requests a particular website, the web browser retrieves the necessary content from a web server and then displays the resulting web page on the user’s device.

A web browser is not the same thing as a search engine, though the two are often confused. For a user, a search engine is just a website, such as Google Search, Bing, or DuckDuckGo, that stores searchable data about other websites. However, to connect to a website’s server and display its web pages, a user must have a web browser installed.

Web browsers are used on a range of devices, including desktops, laptops, tablets, and smartphones. In 2019, an estimated 4.3 billion people used a browser. The most used browser is Google Chrome, with a 64% global market share on all devices, followed by Safari with 17%.

Personal information management (PIM)

Personal information management (PIM) is the activities people perform in order to acquire, organize, maintain, retrieve, and use personal information items such as documents (paper-based and digital), web pages, and email messages for everyday use to complete tasks (work-related or not) and fulfill a person’s various roles (as parent, employee, friend, member of community, etc.). More simply, PIM is the art of getting things done in our lives through information.

Practically, PIM is concerned with how people organize and maintain personal information collections, and methods that can help people in doing so. People may manage information in a variety of settings, for a variety of reasons, and with a variety of types of information. For example, an office worker might manage physical documents in a filing cabinet by placing them in folders organized alphabetically by project name, or might manage digital documents in folders in a hierarchical file system. A parent might collect and organize photographs of their children into a photo album using a temporal organization scheme, or might tag digital photos with the names of the children.

PIM considers not only the methods used to store and organize information, but also is concerned with how people retrieve information from their collections for re-use. For example, the office worker might re-locate a physical document by remembering the name of the project and then finding the appropriate folder by an alphabetical search. On a computer system with a hierarchical file system, a person might need to remember the top-level folder in which a document is located, and then browse through the folder contents to navigate to the desired document. Email systems often support additional methods for re-finding such as fielded search (e.g., search by sender, subject, date). The characteristics of the document types, the data that can be used to describe them (meta-data), and features of the systems used to store and organize them (e.g. fielded search) are all components that may influence how users accomplish personal information management.

Studying, understanding, and practicing PIM can help individuals and organizations work more effectively and efficiently, can help people deal with “information overload”, and can highlight useful strategies for archiving, organizing, and facilitating access to saved information.

Rashumon was a multilingual graphical word processor developed for the Amiga computer by an Israel-based company called HarmonySoft (founded by Michael Haephrati in 1989) and was sold until after the demise of Commodore in 1994 (a lower-priced “student” version was released in 1995). Rashumon had particular support for Hebrew, Arabic and Russian as well as English, and it could send its text to speech synthesis in English.

Rashumon was the only word processor for the Amiga having the ability to create and edit multilingual documents Rashumon printed using Type 1 PostScript fonts and it also supported Intellifont.

Notable Features

• Discontinuous selections: the user can select multiple parts of the text – even if these parts are separated from each other – and perform clipboard manipulations on them (e.g. selecting the first paragraph and the last paragraph of a document at the same time, and copying both of them to the clipboard).
• A Table generator, allowing the creation and editing of tables.
• Multiple key map support, up to 5 simultaneously, allowing for the use of multiple languages simultaneously.
• Search and replace including color, style and font filters. For example, end users could search for the word “Apple” only in green (ignoring this word in other colors) and replace each occurrence with the word “Banana” in yellow.
• Multilingual string gadgets (the Amiga equivalent to text boxes) for creating and renaming files, drawers, etc.
• Import and export multilingual ASCII files to and from PC and Macintosh.
• Fast screen updating and scrolling.
• Interchange File Format (IFF) graphics support (import and export).
• Direct access to 255 characters of each font, similar to inserting “symbols” or “special characters” in modern wordprocessors.

Data Communication System

Data communication refers to the exchange of data between a source and a receiver via form of transmission media such as a wire cable. Data communication is said to be local if communicating devices are in the same building or a similarly restricted geographical area.

The meanings of source and receiver are very simple. The device that transmits the data is known as source and the device that receives the transmitted data is known as receiver. Data communication aims at the transfer of data and maintenance of the data during the process but not the actual generation of the information at the source and receiver.

Datum mean the facts information statistics or the like derived by calculation or experimentation. The facts and information so gathered are processed in accordance with defined systems of procedure. Data can exist in a variety of forms such as numbers, text, bits and bytes. The Figure is an illustration of a simple data communication system.

The term data used to describe information, under whatever form of words you will be using.

A data communication system may collect data from remote locations through data transmission circuits, and then outputs processed results to remote locations. Figure provides a broader view of data communication networks. The different data communication techniques which are presently in widespread use evolved gradually either to improve the data communication techniques already existing or to replace the same with better options and features. Then, there are data communication jargons to contend with such as baud rate, modems, routers, LAN, WAN, TCP/IP, ISDN, during the selection of communication systems. Hence, it becomes necessary to review and understand these terms and gradual development of data communication methods.

Components of data communication system

A Communication system has following components:

1. Message

It is the information or data to be communicated. It can consist of text, numbers, pictures, sound or video or any combination of these.

2. Sender

It is the device/computer that generates and sends that message.

3. Receiver

It is the device or computer that receives the message. The location of receiver computer is generally different from the sender computer. The distance between sender and receiver depends upon the types of network used in between.

4. Medium

It is the channel or physical path through which the message is carried from sender to the receiver. The medium can be wired like twisted pair wire, coaxial cable, fiber-optic cable or wireless like laser, radio waves, and microwaves.

5. Protocol

It is a set of rules that govern the communication between the devices. Both sender and receiver follow same protocols to communicate with each other.

A protocol performs the following functions:

1. Data sequencing

It refers to breaking a long message into smaller packets of fixed size. Data sequencing rules define the method of numbering packets to detect loss or duplication of packets, and to correctly identify packets, which belong to same message.

2. Data routing

Data routing defines the most efficient path between the source and destination.

3. Data formatting

Data formatting rules define which group of bits or characters within packet constitute data, control, addressing, or other information.

4. Flow control

A communication protocol also prevents a fast sender from overwhelming a slow receiver. It ensures resource sharing and protection against traffic congestion by regulating the flow of data on communication lines.

5. Error control

These rules are designed to detect errors in messages and to ensure transmission of correct messages. The most common method is to retransmit erroneous message block. In such a case, a block having error is discarded by the receiver and is retransmitted by the sender.

6. Precedence and order of transmission

These rules ensure that all the nodes get a chance to use the communication lines and other resources of the network based on the priorities assigned to them.

7. Connection establishment and termination

These rules define how connections are established, maintained and terminated when two nodes of a network want to communicate with each other.

8. Data security

Providing data security and privacy is also built into most communication software packages. It prevents access of data by unauthorized users.

9. Log information

Several communication software are designed to develop log information, which consists of all jobs and data communications tasks that have taken place. Such information may be used for charging the users of the network based on their usage of the network resources.