OFFICE AUTOMATION – I COMPUTERS AND APPLICATIONS 14. STORAGE MEDIA A storage medium is any technology (including devices and materials) used to copy, store, and retrieve data. A computer is able to remember and store information in different storage media and which can be recalled and reused whenever required.
14.0 Objectives On completion of this lesson, you will: • • •
Know about the types of memory Recognize the various types of storage media. Know the terminology associated with different forms of media. This lesson is designed to give you a better understanding of how and where the data is stored in the Personal Computer (PC).
14.1 Introduction Storage device as the name implies, is a device for storing data. It usually refers to permanent (non-volatile) storage i.e. the data will remain stored even after the power is removed from the device. A typical way to classify data storage media is to consider its shape and type of movement (or non-movement) relative to the read/write device(s) of the storage apparatus.
14.2 Units of Measurements The data is stored in the memory of the computer in the form of 0 (ZERO) or 1 (ONE) which is knows as “BIT”. 0 or 1 Bit 4 Bits 1 Nibble 8 Bits 1 Byte 1024 Bytes 1 Kilo Bytes (KB) 1024 KB 1 Mega Bytes (MB) 1024 MB 1 Giga Bytes (GB) 1024 GB 1 Terra Bytes (TB)
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14.3 Storage Devices Classification The data in a computer can be stored in different ways: 1. Primary Storage Devices 2. Secondary Storage Devices 14.3.1 Primary Storage Devices 1. You are able to write the information once and after that you are only able to read the information, meaning you can save the information on the device only once. Type of memory: Read Only Memory (ROM) ROM: This is the type of memory in which you save the information on the device, which you, as a user cannot change based upon your requirement. This device (ROM) is generally used in motherboards of the computers, chips of the mobile phones, ipods, calculators etc. 1.
You are able to write, read and edit the information on the device means you can save the information on the device multiple times.
Type of memory: Random Access Memory (RAM) RAM: This is the type of memory in which the data is stored until the device has power. Once the power is switched off, the data stored gets erased automatically. The name Random Access Memory implies that the computer uses this memory very often for the most sought information while processing any task. It is generally used in computers for faster execution of commands by the user. 14.3.2 Secondary Storage Devices Secondary Storage media may be classified into the following: •
Disk storage o Hard disk (magnetic) o Optical disc such as CD-ROM, CD-R, CD-RW, DVD o Floppy disk, ZIP disk (removable and magnetic)
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Flash memory/memory card o Memory stick o Pen Drive
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Tape storage (Obsolete Devices) o Magnetic tape o Paper tape (mechanical)
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Disk storage Disk storage is a group of data storage mechanisms for computers. Data are transferred to planar surfaces or disks for temporary or permanent storage. Disk drive is a peripheral device used to read from and write to a disk. In disk storage, there are two primary access methods: • •
Block storage means that the disk is divided normally into equal-sized blocks and which are accessed at random by the operating system. Access method means content-addressable storage (CAS) which uses a hashing algorithm to refer to pieces of data. Hard Disk Drives (HDD) This is the type of memory in which the data is stored in the device, immaterial of the availability of the power. This means that even if the power is not available to the device, the data remains intact in the device. The storage capacity of the HDD is multiple times more than the storage capacity of the RAM. The computer uses RAM very frequently and the computer saves the information most sought from HDD into the RAM for faster answer of the commands of the user. The Fixed Memory Space in the Computer is referred to as Hard Disk. All information is stored in the Hard Disk of a computer. The information is stored even when the computer is switched off. The memory for Hard Disk is specified in Giga bytes. A hard disk uses platters (disks). Each platter has a planar magnetic surface on which digital data may be stored. Information is written to the disk by a Read-Write head.
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14.3.3 Optical Disks Optical disc is a flat, circular, usually Polycarbonate, disc whereon data is stored. The information on an optical disc is stored sequentially on a continuous spiral track from the innermost track to the outermost track. CD ROM The CD-ROM is an abbreviation for "Compact Disc Read-only Memory". Computers can generally read audio CDs. It is possible to produce composite CDs containing both data and audio with the latter capable of being played on a CD player, whilst data or perhaps video can be viewed on a computer. The standard CD-ROM holds 650 (333,000 sectors) or 700 MB of data. One track generally consists of 16-20 sectors. The CD-ROM is popular for distribution of software, especially multimedia applications, and large databases. A CD weighs less than 30 grams. A CD-R (Compact Disc-Recordable) is a variation of the Compact Disc digital audio disc invented by Philips and Sony. The CD-R retains all the abilities of the CD standard but adds the functionality of being able to store either music or data. A Compact Disc Rewritable (CD-RW) is a rewritable optical disc. Known as CD-Erasable (CD-E) during its development phase, it was introduced in 1997. A CDRW recorder can rewrite 700 MB of data to a CD-RW disc roughly 1000 times. A DVD (sometimes known as the "Digital Video Disc" or "Digital Versatile Disc") is an optical disc storage media format that can be used for data storage, including movies with high video and sound quality. DVDs resemble compact discs as their physical dimensions are the same (12 cm (4.72 inches) or occasionally 8 cm (3.15 inches) in diameter) but they are encoded in a different format and at a much higher density.
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A single-layer DVD can store 4.7 GB (4.38 GB, or 4,707,000,000 Bytes), which is around seven times as much as a standard CD-ROM. Floppy Disk A floppy disk is a data storage device that is composed of a ring of thin, flexible (i.e. "floppy") magnetic storage medium encased in a square or rectangular plastic wallet. Floppy disks are read and written by a floppy disk drive or FDD. In general, data is written to floppy disks in a series of sectors, angular blocks of the disk, and in tracks, concentric rings at a constant radius. For example the HD format of 3½-inch floppy disks uses 512 bytes per sector, 18 sectors per track, 80 tracks per side and two sides, for a total of 1,474,560 bytes per disk (i.e. 1.44 MB). ZIP Drive The Zip drive is a medium-capacity removable disk storage system, introduced by Iomega in late 1994. Originally it had a capacity of 100 MB, but later versions increased this to first 250 MB and then 750 MB. The format became the most popular of the super-floppy type products but never reached a quasi-standard status to replace the 3.5-inch floppy disk.
14.3.4 Flash Memory/Memory Card Flash memory is a form of EEPROM (Electrically Erasable Programmable Read-Only Memory) that allows multiple memory locations to be erased or written in one programming operation. In layman's terms, it is a form of rewritable memory chip that holds its content without the need of a power supply. It is also an example of a Non-Volatile Read Write Memory (NVRWM). The memory is commonly used in Memory cards, USB flash drives, MP3 players, Digital cameras and Mobile phones. Memory Stick Memory Stick is a removable flash memory card format, launched by Sony in October 1998, and this name is generally used to describe the family of Memory Cards. Typically, a Memory Card is a portable device used 5
specifically as a storage media. It can be attached easily to the PC at any of the USB ports and can be removed easily. It is generally used in Digital Cameras, Mobile Phones to store pictures or image files. The data can be written on these sticks @ 1.8MBPS, and can be read @ 2.5MBPS. The storage capacity varies from 128MB to many GBs and it is generally the size of a “Chewing Gum”. These memory sticks are available in the market in many variants: 1. 2. 3. 4. 5.
Memory Stick Select Memory Stick PRO Memory Stick Duo Memory Stick Micro (M2) Memory Stick PRO-HG This is the latest invention with a write speed of 120 Mbps. Pen Drive A USB flash drive is essentially a flash memory used as a small, lightweight, removable data storage device of up to 64 GB. It is used to store any kind of data unlike memory sticks. USB flash drives use the USB mass storage standard for removable storage devices. USB flash drives are also known as "pen drives", "chip sticks", "thumb drives", "flash drives", "USB keys", and a wide variety of other names. They require no other external power source or battery power source. These drives have become a fashion statement today. They are available in the market in very stylish shapes. One of them is shown here. The common uses of the device are as follows: 1. 2. 3. 4. 5.
Personal data transfer Carry applications (like Virus Scanners, Adobe Acrobat etc.) As MP3 Players Computer Repairs (transfer recovery and antivirus software) System Administration
This device has a durable solid state design, which makes it ideal for transferring personal or work files from one location to another location. As these devices are generally plug-n-play devices, they carry huge demand in the general user segment. These drives are relatively, a dense form of storage and the cheapest form of this device is able to store data equivalent to data in 100’s of floppy drives, which makes it more sought by the general user segment.
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Flash drives can tolerate nominal physical impacts, and minor mishandling compared to the hard disk drives. But the device can stop working or data can be corrupted by severe physical impacts, improperly wired USB ports, removing the flash drive when the computer is reading from it. 14.3.5 Tape Storage (Obsolete Devices)
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Tape storage is long, thin, flexible, linearly moving bands. These can be divided into two categories: Paper tape and Magnetic tape Punched Tape Punched tape is largely, an obsolete technology of data storage. It consists of a long strip of paper in which holes are punched to store data. It was widely used for most of the twentieth century for teleprinter communication, and later as a storage medium for minicomputers and CNC machine tools.
Magnetic Tape Magnetic tape is a non-volatile storage medium consisting of a magnetic coating on a thin plastic strip. Nearly all recording tape is of this type, whether it is used for video, audio or general purpose digital data storage, using a computer. Magneto-optical and optical tape storage products have been developed using similar concept as magnetic storage, but have achieved very little commercial success.
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Self-Check Questions Fill in the Blanks 1. The memory for Hard Disk is specified in ______________ 2. The standard CD-ROM holds ____________ (333,000 sectors) _____________ of data. 3. A Pen Drive is a removable data storage device of up to _______GB. 4. A Floppy Drive is a removable data storage device of up to _____MB. 5. 1 Mega byte (MB) = __________________Bytes.
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Match the following 6. 7. 8. 9.
HDD CDROM Pen Drive Floppy Drive
a. b. c. d.
64 GB Fixed Memory 1.44 MB 650 MB
Select the right answer 10. Pen Drive is a a. Fixed Memory b. Flash Memory c. Both d. None 11. ZIP Drive have latest data storage capacity of a. 100 MB b. 250 MB c. 650 MB d. 700 MB True or False 12. Hard Disk Drive is a memory card. ( ) 13. Zip drive is a removable data storage device. ( ) 14. A single-layer DVD can store 4.7 GB ( )
14.4 Summing Up In this lesson you have familiarized yourself with the following concepts in storage media: Disk storage
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Flash memory/memory card Tape storage
14.5 Answer to Self-Check Questions 1. Giga Bytes 2. 650 or 700 MB 3. 64 GB 4. 1.44 MB 5. 1048576 Bytes 6. B 7. D 8. A 9. C 10. B 11. D 12. F 13. T 14. T
14.6 Terminal Questions 1. 2. 3. 4.
What are the different types of storage media? What is a CD ROM? What is a Pen Drive? What is a Magnetic Tape?
14.7 Glossary MB – Megabytes i.e. 1024 Bytes, 1 byte is equal to 8 bits. GB – Gigabytes i.e. 1024 MB Hard disk, CD-ROM, CD-R, CD-RW, DVD, Floppy disk, ZIP disk, Memory stick, USB Keydrive , Magnetic tape, Paper tape.
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