INFS 214: Introduction to ComputingPrimary storage is therefore said to be volatile. It loses all of its contents when power to the system unit is shut off or disrupted. • This volatility

College of Education

School of Continuing and Distance Education 2014/2015 – 2016/2017

INFS 214:

Introduction to Computing

Session 6 – Storage Technologies

Lecturer: Dr. Ebenezer Ankrah, Dept. of Information Studies Contact Information: [email protected]

Session Overview

• A very important feature of a very computer is the ability to save, or store information. This is done by the storage devices. This session explains the types and categories of storage devices that are used in the computer environment.

• At the end of the session, the student will – Understand and differentiate between the various types of storage

devices

– Be able to give examples of storage devices

– Understand the different characteristics of storage devices

– Be able to identify the components of some of the storage devices

– Be able to differentiate between technologies underpinning the storage devices

DR. EBENEZER ANKRAH Slide 2

Session Outline

The key topics to be covered in the session are as follows:

• Introduction to Storage Devices

• Magnetic Disk

• Optical Disc


Reading List

• Hutchinson, S. E., & Sawyer, S. C. (2013). Computers: The user perspective. Boston: Irwin McGraw-Hill. (Chapter 4)

• O’Leary, T. J., & O’Leary, L. I. (2014). Computer Today. Boston: McGraw Hill. (Chapter 9)

• Williams, B. K., & Sawyer, S. C. (2014). Using Information Technology: A practical introduction to computers and communications (11th ed.). McGraw-Hill Education. (Chapter 5)


INTRODUCTION TO STORAGE DEVICES

Topic One


Introduction to Storage Devices

• A very important feature of a very computer is the ability to save, or store information. This is done on the storage devices. Computer memory is also known as primary storage. It is usually referred to as Random Access Memory (RAM). It is closely related to the central processing unit but separate from it.

• Memory holds the data when; – It is input to the system and before it is processed.

– After it has been processed but before it has been released to the output device.

– Holds the programmes (computer instructions) needed by the central processing unit.



• Memory consists of electronic circuits, just as the CPU does. Memory electronically stores letters, special characters such as cedi signs and decimal points, and images.

• Turning on a personal computer activates its memory, turning it off causes anything stored in memory to disappear. Primary storage is therefore said to be volatile. It loses all of its contents when power to the system unit is shut off or disrupted.

• This volatility results in a need for more permanent or non-volatile storage. This need for other storage devices for long-term storage of data that can be reused is provided by secondary storage devices.



• Storage devices are devices that store data/information (all things being equal). There are two types of storage technologies - the magnetic and the optical. The capacity of the storage device is measured in bytes. It ranges from kilobyte to megabyte, gigabyte, terabyte, etc.



• The memory unit of a digital computer typically has a main (or primary) memory, cache, and secondary (or auxiliary) memory.

• The main memory holds data and instructions for immediate use by the computer’s ALU. It receives this information from an input device or an auxiliary storage unit.

• In most cases, the main memory is a high-speed random-access memory (RAM) — i.e., a memory in which specific contents can be accessed (read or written) directly in a very short time regardless of the sequence (and hence location) in which they were recorded.



• Two types of main memory are possible with random-access circuits

– Static random-access memory (SRAM) and

– Dynamic random-access memory (DRAM).



• The cache is an extremely fast part of the main memory. In SRAM-based memory, it is of small capacity that has faster access time than the main memory and that temporarily stores data and part of a program for quicker processing by the ALU.

• Secondary storage provides permanent or non-volatile

storage. Using secondary storage devices, data and programmes can be retained after the computer has been shut off. This is accomplished by writing and reading files. Writing is the process of saving information. Reading is the process of accessing information.



• Characteristics of Secondary Storage

– Media or Medium: is the actual physical material that holds the data and programs.

– Capacity: measures how much a particular storage medium can hold.

– Read/Write: Storage devices are hardware that reads data and programmes from storage media. Most also write to storage media.

– Access speed or Access time: measures the amount of time required by the storage device to retrieve data and programs.


Questions

• Individual Assignment:

– List some of the magnetic disks

• Forum Question:

– Distinguish between magnetic technology and optical technology


MAGNETIC DISK Topic Two


Magnetic Disk

• A magnetic disk is a storage device that uses a magnetization process to write, rewrite and access data. It is covered with a magnetic coating and stores data in the form of tracks, spots and sectors. Hard disks, zip disks and floppy disks are common examples of magnetic disks.

• A memory device, such as a floppy disk, a hard disk, or a removable cartridge, that is covered with a magnetic coating on which digital information is stored in the form of microscopic, magnetized regions.


Magnetic Disk

• Floppy Disks • Floppy disks are removable storage media. The traditional floppy

disk holds 1.44 MB. High capacity floppy disks hold much more. As a result of the small amount of data that they can contain, they are almost phased out and replaced by other types.

• Floppy disks, often called diskettes or simply disks, are portable or removable storage media. They are typically used to store and transport word processing, spreadsheet, and other types of files.

• They use flat circular pieces of Mylar plastic that have been coated with a magnetic material. Floppy Disk Drives (FDD) store data and programs by altering the electromagnetic charges on the disk’s surface to represent ones and zeros.


Magnetic Disk

• Floppy disks are also called flexible disks and floppies. This is because the plastic disk inside the diskette cover is flexible, not rigid. There are several types of floppy disks with different capacities ranging from the traditional floppy disk to a variety of high capacity floppy disks.

• • The traditional floppy disk is the 1.44 MB 3½-inch disk.

Al-though introduced over 20 years ago, they are still in use. The most common type is labelled 2HD, which means “two-sided, high-density.” Two-sided indicates that data can be stored on both sides of the disk. Density refers to how tightly the bits (electromagnetic charges) can be packed next to one an-other.


Magnetic Disk

• Zip disks are produced by Iomega and typically have a 100 MB, 250 MB, or 750MB capacity. Internal Zip drives are a standard feature on many of today’s system units. External Zip drives are generally connected to the system unit using a USB port.


Magnetic Disk

• HiFD disks from the Sony Corporation have a capacity of 200 MB or 720MB. They have one major advantage over Zip disks. Their drives are able to read and store data on today's 1.44 MB traditional disk as well as on their own higher capacity disks.

• Super Disks are produced by Imation and have a 120 MB or 240 MB capacity. Like HiFD drives, Super Disk disk drives are able to use today's 1.44 MB standard disks. Each of these will likely improve its capacity and speed in the near future.


Magnetic Disk

• Hard Disks • While internal hard disks provide fast access, they have a

fixed amount of storage and cannot be easily removed from the system cabinet. Hard-disk cartridges, also known as removable hard disks, are as easy to remove as a cassette from a videocassette recorder.

• The amount of storage available to a computer system is limited only by the number of cartridges. Hard-disk cartridges are used primarily to complement an internal hard disk. Because the cartridges are easily removed, they are particularly useful to protect or secure sensitive information.


Magnetic Disk

• Pc Cards Credit card-size hard-disk cartridges called PC Card hard disks are available for notebook computers with typical capacities up to 5 giga-bytes. Two well-known PC Card hard disks are IBM's Micro drive and Toshiba's MKS002.


Magnetic Disk

• Hard-disk packs are removable storage devices used to store massive amounts of information. Their capacity far exceeds the other types of hard disks. Although you may never have seen one, it is almost certain that you have used them.

• Microcomputers that have access to the Internet, minicomputers, or mainframes often have access to external hard-disk packs through communication lines. Banks and credit card companies use them to record financial information.


OPTICAL DISC Topic Three


Optical Disc

• OPTICAL DISKS

• Optical disks use laser technology to provide high capacity storage. CD and DVD are optical disk formats. Data Play disks are for digital photography and music.

• Today's optical disks can hold up to fifty gigabytes of data. That is the equivalent of over several million typewritten pages or a medium -sized library all on a single disk.


Optical Disc

• Compact Disk

• Compact disc (CD), used to be one of the most widely used optical formats. CD drives are standard on many microcomputer systems. Typically, CD drives can store from 650 MB (megabytes) to 1 GB (gigabyte) of data on one side of a CD.

• One important characteristic of CD drives is their rotational speed. This speed is important because it determines how fast data can be transferred from the CD.


Optical Disc

• For example, a 24X or 24-speed CD drive can transfer 3.6 MB per second, while a 48X drive can transfer 7.2 MB per second. The faster the drive, the faster data can be read from the CD and used by the computer system.

• There are four basic types of CDs: These are Read only, Write once, Rewritable and Picture and Photo CDs.


Optical Disc

• Read Only CD ROM

• Read Only CD ROM Stands for compact disc-read only memory, it is similar to a commercial music CD. Read only CD means it cannot be written on or erased by the user.

• Thus, you as a user have access only to the data imprinted by the publisher. CD-ROMs are used to distribute large databases and references. They are also used to distribute large software application packages.


Optical Disc

• Write Once CD

• Write Once-CD-R, which stands for CD-recordable, can be written to once. After that they can be read many times without deterioration but cannot be written on or erased.

• CD-R drives, also known as CD burners, are often used to archive data and to record music downloaded from the Internet.


Optical Disc

• Rewritable CD • Rewriteable-CD-RW stands for compact disc rewritable.

Also known as erasable optical disks, these disks are very similar to CD-Rs except that the disk surface is not permanently altered when data is recorded.

• Because they can be changed, CD-RWs are often used to create and edit multimedia presentations. One limitation of CD-R and CD-RW disks is that older CD-ROM drives may not be able to read them. Most newer CD-ROM drives are multi-read or able to read both CD-R and CD-RW disks.


Optical Disc

• Picture & Photo CDs • Picture CDs and Photo CDs use a special format developed by

Eastman Kodak to store digital images. Picture CDs are less expensive and typically used by non-professionals.

• Today, most film developers provide traditional printed pictures and digital images. The digital images are delivered by the Internet or by Picture CD.

• These disks are typically single-session, meaning that all images must be transferred at one time to the CD. Photo CDs, however, are multi-session, meaning that new images can be added at any time.


Optical Disc

• Digital Versatile Disc • DVD stands for digital versatile disc or digital video disc.

This is a format that is rapidly replacing CDs as the standard optical disk.

• DVD drives are very similar to CDs except that more data can be packed into the same amount of space. DVD discs can store 4.7 GB to 17 GB on a single DVD disk, about -17 times the capacity of CDs.

• There are three basic types of DVDs similar to CDs: read only, write once, and rewriteable.


Optical Disc

• Read Only DVD-ROM • Read only-DVD-ROM stands For Digital Versatile Disc Read

Only Memory. DVD-ROM drives are also known as DVD players. DVD-ROMs are having a major impact on the video market.

• While CD-ROMs are effective for distributing music, they can only contain just over an hour of fair quality video. DVD-ROMs can provide over two hours of very high-quality video and sound comparable to that found in motion picture theatres.

• The motion picture industry has shifted video distribution from video cassettes to DVD-ROMs.


Optical Disc

• Write Once

• Write once-DVD-R, DVD+R and DVD+R DL are competing write once formats. All stand for DVD recordable. Each has a slightly different way in which they format their disks.

• Fortunately, most new DVD players can use either format. DVD-R and DVD+ R drives are typically used to create permanent archives for large amounts of data and to record videos.

• The DVD+R DL stores up to 8.5 GB because the DL stands for double layer


Optical Disc

• Rewriteable DVD

• Rewriteable DVD - Unfortunately, there are several competing rewriteable formats and few DVD players can read all the standards.

• The three most widely used formats are DVD-RW, DVD+RW, and DVD-RAM. DVD-RW and DVD+ RW stand for DVD rewritable. DVD-RAM stands for DVD random-access memory.


Other Types of Secondary Storage

• Other types of secondary storage are:

– Solid-state storage does not have moving parts.

– Internet drives use the Internet to store data and information.

– Magnetic tape provides sequential access for backup.

– Blu-Ray Technology is a new optical technology emerging.


Optical Disc

• Solid-state storage does not have moving parts.

• Internet drives use the Internet to store data and information.

• Magnetic tape provides sequential access for backup.

• Blu-Ray Technology


References

• Hutchinson, S. E., & Sawyer, S. C. (2013). Computers: The user perspective. Boston: Irwin McGraw-Hill.

• O’Leary, T. J., & O’Leary, L. I. (2014). Computer Today. Boston: McGraw Hill.

• Williams, B. K., & Sawyer, S. C. (2014). Using Information Technology: A practical introduction to computers and communications (11th ed.). McGraw-Hill Education.


Documents

INFS 214: Introduction to ComputingPrimary storage is therefore said to be volatile. It loses all of its contents when power to the system unit is shut off or disrupted. • This volatility