Monday, 3 November 2014

Introduction to Understanding Digital Media Devices of all eras

This chapter focuses on the various types of digital media devices. Users can store different types of data on these devices, including pictures, videos, music, text, and applications. The chapter covers older digital media, such as magnetic tapes and floppy disks, before moving on to a discussion of optical discs, such as CDs and DVDs, and devices such as digital audio players and flash drives.
Magnetic Tapes
A magnetic tape is a recording medium that consists of a thin plastic strip with a coating of a fine magnetic material. It is generally used for recording audio, video, and digital data.
The magnetic layer consists of a magnetic pigment suspended within a polymer binder. As the name implies, the binder holds the magnetic particles and tape backing together.
Data is stored in frames across the width of a tape. The frames are grouped into blocks, or records, which are separated by gaps.
A magnetic tape is a serial access medium. If someone wants to find a particular piece of data on a tape, the tape drive has to start at the beginning of the tape and search until it finds that data. However, large amounts of information can be stored on a magnetic tape. This feature has made it an excellent choice for the regular backup of hard disks.
Floppy Disks
A floppy disk is a small, portable magnetic disk that is used to store and transfer computer data. It is also called a diskette or floppy. The access speed of a floppy disk is slow when compared to that of a hard disk. The storage capacity of a floppy disk is lower than that of a hard disk, but floppies are not as expensive as hard disks.
The following are the basic sizes of floppy disks:
• 8-inch: Created in 1971, this type of floppy consists of a magnetic storage medium enclosed in a cardboard case. It is capable of storing up to 1 MB of data.
• 5¼-inch: Designed in 1976, this type of floppy has types capable of storing from 100 KB to 1.2 MB of data.
• 3½-inch: Made in 1987, this type of floppy is enclosed in a rigid plastic envelope. It is also called a micro floppy. Despite its smaller size, it stores a larger amount of data, generally between 720 KB and 1.4 MB.
Compact Discs
A compact disc (CD) is a polycarbonate plastic disc with one or more metal layers that is used for storing digital data. It is a standard medium for distributing large quantities of information in a dependable package. The diameter of a standard CD is 120 mm, and the diameter of a mini CD is 80 mm.
Polycarbonate plastic (substrate layer) is impressed with microscopic bumps that are arranged as a single continuous spiral track of data. The polycarbonate plastic is coated with a thin aluminum (reflective) layer that covers the bumps. Then a thin acrylic (protective) layer is sprayed over the aluminum. The label is then printed on the acrylic layer.
The single track of data spirals from the center of the disc to the outside edge. The extended bumps that make up the track are 0.5 microns wide, 0.83 microns long, and 125 nanometers high.
Types of Compact Discs
There are different types of compact discs used for data storage. The following are some of the more common types:
• CD-ROM (compact disc read-only memory): This is the most basic type of optical disc used with computers.
The most common CD-ROM format holds 700 MB of data. When a user purchases a CD-ROM, it already has the data on it. A user cannot write new data to the disc.HD DVDs HD DVDs were originally called Advanced Optical Discs (AODs) and were developed as a successor to standard DVDs. An HD DVD is the same physical size as a standard DVD (120 mm), but it holds more data. Whereas a DVD holds up to 4.7 GB of data per layer, an HD DVD holds up to 15 GB per layer.
It has a bumpy layer that reflects light from a laser to a sensor, which creates a digital signal.

HD DVDs store more data than DVDs for the following reasons:
• HD DVDs use 405-nanometer blue-violet lasers instead of 650-nanometer red lasers.
• Because of the shorter wavelength lasers, the pits used in HD DVDs can be smaller and arranged closer together. Whereas the track pitch of a standard DVD is 0.74 microns, the track pitch of an HD DVD is 0.4 microns.
• HD DVDs use more efficient compression techniques to reduce the sizes of the files they store.
Blu-ray Discs
Blu-ray is the next-generation optical medium patented by Sony. A Blu-ray disc holds a large amount of data and is generally used to store high-definition video and audio. The laser used to read the data is focused on smaller areas, so more data can be stored on a disc that is the same size as a CD or DVD. Blu-ray discs are not readable on standard CD and DVD players and readers.

The following are the specifications for Blu-ray:
• Recording capacity: 27 GB
• Laser wavelength: 405 nm (blue-violet laser)
• Lens numerical aperture (NA): 0.85
• Data transfer rate: 36 Mbps
• Disc diameter: 120 mm
• Disc thickness: 1.2 mm
• Protection layer thickness: 0.1 mm
• Minimum pit length: 0.15 microns
• Track pitch: 0.32 microns
• Recording format: Phase change recording
• Tracking format: Groove recording
• Video recording format: MPEG2 video
• Audio recording format: AC3, MPEG1, and Layer 2
• Video and audio multiplexing format: MPEG2 transport stream
A single-layer Blu-ray disc holds 27 GB of data, and a dual-layer Blu-ray disc holds 50 GB of data. The format also offers interactive features that allow users to connect to the Internet and directly download subtitles and other movie features.

The following are the advantages of Blu-ray:
• A user can record high-definition television (HDTV) without any quality loss.
• A user can instantly skip to any spot on a disc.
• A user can record one program on a disc, even if he or she is watching another one.
• It generates playlists.
• It edits or reorders the programs that are recorded on a disc.
• It automatically searches for an unfilled space on a disc to avoid recording over a program.
• A user can access the Web to download subtitles and other additional features.
The iPod is a class of portable digital audio players that are designed and marketed by Apple Computer. The user interface is designed around a central scroll wheel.
The standard iPod stores media on a built-in hard drive, but the smaller iPod shuffle and iPod nano se flash memory. Apple iPods operate as external data storage devices when connected to a computer.
iPods support various audio file formats. For formats that aren’t supported, such as Ogg Vorbis, FLAC, and Windows Media Audio (WMA), the file has to be converted to a compatible format before it is placed on an iPod. A user can use iTunes, the digital media player application most commonly used to interact with an iPod,
to perform this conversion.

The following are the file formats iPods support:
• MP3
• Protected AAC
• Audible audiobook
• Apple Lossless
The following are the features of iPods:
• They are used to play music files and videos.
• They are used to store pictures.
• They are used to store backup data files.
• They are used to store addresses and contacts.
• They are used to play games.
• They have up to 20 hours of battery life.
• Their storage capacities range from 1 GB to 120 GB, and this increases with each new iteration.
• They act as mass storage devices. The iPod uses the Apple HFS file system when the device is run with a Mac, and the FAT32 file system when it is used with a Windows PC.
The Zune is a portable digital music player that was developed by the Microsoft Corporation. It can hold 30 GB of data. Figure 2-2 shows a Zune.

The following are the features of Zune:
• It takes digital photos.
• It contains a three-inch LCD video screen that works in portrait mode to view pictures and videos.
• It contains a built-in FM tuner that works with American, Japanese, and European frequencies.
• A user can share full-length tracks, home recordings, playlists, and pictures wirelessly from one Zune player to another.
Flash Memory Cards
Flash memory cards are solid-state electronic flash memory data storage devices. They are used in digital cameras, cell phones, handheld devices, laptop computers, digital music players, video game consoles, and other electronic devices. Each sector of flash memory can be erased and written to only a limited number of times.

There are various types of flash memory cards, all with different storage capacities and features.

Secure Digital (SD)
An SD card is small and thin. A standard SD card is 32 mm long, 24 mm wide, and 2.1 mm thick. A mini SD card is 21.5 mm long, 20 mm wide, and 1.4 mm thick.

This type of card has storage capacities ranging from 8 MB to 4 GB. It also supports digital rights management (DRM) technology. SD cards usually come preformatted with the FAT32 file system. SDHC cards support capacities greater than 4 GB.

These cards are not compatible with older devices that accept SD cards. However, SDHC readers accept older SD cards. The SD interface has also been used for SDIO devices, which are small devices such as GPS receivers, Bluetooth adapters, Ethernet adapters, and FM tuners that are compatible with the SD standard.

CompactFlash (CF)
There are two types of CF cards: Type I cards are 3.3 mm thick, and Type II cards are 5 mm thick. CF is one of the older flash memory types. The cards are larger than most of the newer types, but people still use this type of card because of its large capacity and low cost. CF cards have storage capacities ranging from 2 MB to 100 GB.

CF cards have a controller chip that attempts to prevent the premature wearing out of a particular sector by spreading the data out over the device when writing. Microdrives, which are miniature hard disks, were designed to fit into Type II slots, and CF cards can easily fit into a PC Card slot with an adapter.

Memory Stick (MS)
There are various types of Memory Sticks, with capacities ranging from 4 MB to 32 GB. These cards are typically used with digital cameras, PDAs, and the Playstation Portable (PSP). Memory Sticks support high-speed data transfers, with a maximum speed of 160 Mbps.

MultiMediaCard (MMC)
An MMC is 32 mm long, 24 mm wide, and 1.4 mm thick, so it is almost the same size as an SD card. The SD format is actually a successor to MMC, and MMCs can fit into most devices that support SD cards. MMC supports storage capacities up to 8 GB. Figure 2-6 shows an MMC.

xD-Picture Card (xD)
An xD-Picture Card is 20 mm long, 25 mm wide, and 1.78 mm thick. The xD-Picture Card format supports storage capacities up to 8 GB. As the name implies, these cards are used primarily in digital cameras, particularly those made by Olympus and Fujifilm, developers of the format. Some cameras that use xD cards use the cards to provide certain photographic features, such as a panoramic function. xD cards support fast data transfer rates,
and they are smaller than many older card types.

SmartMedia (SM)
SM cards are 45 mm long, 37 mm wide, and 0.76 mm thick. The storage capacities of SM cards range from 2 MB to 128 MB. These cards can be used with PC Card slots, CF Type II slots, and 3½-inch floppy drives using adapters. Its larger size makes it impractical for use in most modern devices. Figure 2-8 shows an
SM card.

USB Flash Drives
USB flash drives are NAND-type flash memory data storage devices integrated with a USB 1.1 or 2.0 interface.
They are small in size, lightweight, easily detachable, and rewritable. The storage capacities of USB drives typically range from 8 MB to 64 GB.
They are usually used for relatively quick portable storage and have replaced the floppy disk for this purpose.
They use the USB mass storage standard, which is supported by the latest versions of operating systems such as Linux, Mac OS, and Windows.
They are also known as pen drives, thumb drives, jump drives, USB keys, USB sticks, key drives, and vault drives.
A USB flash drive consists of a small printed circuit board enclosed in a robust plastic or metal casing.
The USB connector is usually protected by a detachable cap. A USB drive does not require batteries and instead gets its power from the device it is connected to.
To access the data that is stored on a flash drive, a user must connect the drive to a USB port or USB hub attached to a computer or some other device.

The following are the components of a USB flash drive:
• Male type-A USB connector
• USB mass storage controller
• Jumpers and test pins
• NAND flash memory chip
• Crystal oscillator
• Write-protect switches

The following are the common uses of USB flash drives:
• To transfer data from one computer to another
• To perform system administration tasks
• To transfer applications
• To hold music
• To boot operating systems

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