Common Storage Devices (Lesson 3-1) Classifying Storage Devices

Common Storage Devices (Lesson 3-1) Classifying Storage Devices
Common Storage Devices (Lesson 3-1)
Classifying Storage Devices (Lesson 3-2)
Common Storage Devices (Lesson 3-3)
Computer Fundamentals
Common Storage Devices
Objectives:
Explain the need for storage devices for computers.
Distinguish between memory and storage.
Distinguish between storage devices and media.
Key Terms:
• storage device
• memory
• Basic Input/Output System (BIOS)
• file
Compare and Contrast
Backpack
Storage Device
What are Storage Devices?
They are the computer's hardware
components that retain data
even after the power is turned off.
System Startup
Computer storage devices are a key part of a computer's startup
process. Without a storage device to hold startup information
permanently, a computer would not know what to do when you
turned it on.
When you start a computer, it looks for information that tells it what
to do. The Basic Input/Output System, or BIOS, is a set of
programs that tells the computer equipment how to start up.
Connections
Science The study of memory does not only apply to computer
science. Some psychologists have noted similarities in the ways
human and computer memories function.
Some research supports an input output model of human memory.
They see memory as a storage device that is limited in capacity.
According to this theory, how much a person can learn (input)
may be limited by how much he or she forgets (output).
Memory VS Storage
When people talk about computer memory, they
usually mean a set of chips that acts as a temporary
workspace in the computer.
This memory, called random access memory, or RAM,
stores data and program instructions needed by the
CPU.
RAM holds data and programs while they are being
used. As you use the computer, you constantly work
with the contents of RAM.
Storage VS Memory
Differences between storage and memory:
• The two work differently. Remember that RAM uses chips to temporarily
store information. These chips depend on a constant supply of power
to keep their contents; when the power is lost, the chips lose their
contents.
Storage uses different methods to store information permanently, so it
isn't lost when the power is turned off.
• A PC has more storage capacity than memory. Even though some PCs
can hold as much as 1GB of RAM, their hard drives will be many times
larger.
Storage Media and Storage Devices
Storage has two components: storage media and storage devices.
Storage Media
In terms of storage, a medium is an object that physically holds
information or program instructions. Floppy disks, magnetic tapes, and
compact discs are examples of storage media. (The word media is the
plural of medium.)
Storage Devices
A storage device is a piece of hardware that holds the storage
medium, sends data to the medium, and retrieves data from the
medium. Floppy disk drives, hard drives, CD-ROM and DVD-ROM
drives, and tape drives are all examples of storage devices.
Classifying Storage Devices
Objectives:
Explain how computer storage devices are
classified.
Compare and contrast primary, secondary,
and archival storage devices.
Describe other categories of storage devices.
Key Terms:
• primary storage • secondary storage • archival storage
• read-only device • read/write device • sequential storage device
• random access storage device • optical storage device
Hierarchy of Storage Devices
Computer storage devices are sometimes classified in a hierarchical
structure that is, primary or secondary.
Which are the PRIMARY “Storage Devices”?
The term primary storage is sometimes used to Describe the main memory,
or RAM, in a computer. This is because when the CPU needs data or
instructions, it looks in memory before looking anywhere else. Most
knowledgeable computer users, however, avoid using the term storage when
talking about RAM. This is because RAM works very differently from storage
devices such as disks or tapes. RAM also loses any data it contains when the
computer is turned off, while disks and tapes can hold data permanently.
Hierarchy of Storage Devices
Which are the SECONDARY Storage Devices”?
The term secondary storage is sometimes used to describe devices that can
store data permanently, such as a hard drive, floppy disk, compact disc, or
tape. This is because the computer will look for data on one of these
devices if the data is not in RAM. Many kinds of secondary storage devices
can hold much more data than a computer's RAM can. Because they can
store information permanently (or until you erase it), secondary storage
devices are sometimes called archival storage devices. This refers to the
fact that you can store information on a disk or tape and then put it away for a
long time, only using it again when you need it.
Categories of Storage Devices
Storage devices are divided into three categories. Each category has two
options based on the device.
Read-Only Versus Read/Write
A read-only device can only read information from the storage medium. You
cannot change the information on the medium or save new information onto it.
A CD-ROM drive is an example of a read-only device, because it does not have the
capability to write information onto a disc.
The media used with read-only devices come with information already saved on
them. Music CDs or software programs on CDs are CD-Rs. Your CD-ROM
drive will be able to play the music or read the program instructions from the
disc, but you can't change The disc's contents. Standard DVD players are
another example f a read-only device.
Categories of Storage Devices
Read-Only Versus Read/Write
A read/write device not only can read information from the storage
medium, but can write information onto the medium, as well. These
devices let you read information from a disk or tape, make changes
to the information, and save new information onto the medium.
Hard drives, Floppy disk drives, tape drives, CD-Rewritable
drives (CD-RW), and DVD-RAM drives are commonly used
examples of read/write devices.
Categories of Storage Devices
Sequential Versus Random Access
When equipped with a tape drive, a computer can store information on a long piece
of tape, similar to a cassette tape. A tape drive is an example of a sequential
storage device, which requires the computer to scan from the beginning of
the medium to the end until it finds the information it needs. This type of storage is
cheaper but slower than other types of storage. Today's computer tapes can
store 200 GB or more of information. But it can take several minutes to locate a
piece of information on a high-capacity tape.
A random access storage device lets a computer go directly to the needed
information. The device does not have to search the entire medium to find
information. For this reason, random access storage devices are much faster, and
more expensive, than sequential devices. A hard drive is an example of a
random access storage device.
Categories of Storage Devices
Magnetic Versus Optical Storage
Magnetic storage devices are specially treated disks or tapes that record
Information using magnetically sensitive materials. These devices use
electricity to shift magnetic particles so they form a pattern. That way, the
computer can read and store the information. Common magnetic storage
devices include hard drives, floppy disk drives, and tape drives.
Other storage devices use laser beams to read information that has been
stored on the reflective surface of a disk. These are called optical storage
devices. Popular types of optical storage devices for computers include
CD-ROM and DVD-ROM drives.
Do you think Ipods are “Storage Devices”?
Why?
How can we categorize them?
Common Storage Devices
Objectives:
Differentiate between internal and external storage
devices.
List commonly used magnetic storage devices.
Summarize optical storage options.
Key Terms:
• hard drive
• floppy disk drive
• CD-ROM drive
Internal and External Storage Devices
An internal storage device is a
device installed inside your computer
An external storage device is a device
positioned outside your computer
-Internal & External Storage Devices can be
installed or connected to your computer
Magnetic Storage Devices
Magnetic Storage Devices are a storage
device that is installed in your computer.
Hard Drive
-The most common magnetic storage device is
a hard drive
Magnetic Storage Devices
Floppy Disk Drives
A floppy disk drive is a storage device with a
slot that accepts floppy disks. Often internal,
but can also be external.
Magneto–Optical Storage Devices
Zip and Jaz Drives
Other forms of magnetic storage devices are
Apple's iPod, a portable storage/playback
device, and Zip and Jaz drives. These drives
are similar to floppy disk drives; however, they
are slightly larger in size and use a special disk
or cartridge to store much more information
often 100 times more!
Magneto-Optical (MO) Drives
This drive combines both magnetic & optical
drive technologies.
It uses a removable disk that is inserted in a
slot in front of the drive.
Can be internal or External.
Their disks can store several gigabytes of
information.
Online Storage
It is a storage that can be used in a remote
computer.
Usually located in the internet
Common Optical Storage Devices
Let you store a lot of info and lets it be transported easily
Most commonly known: CD-ROM drive
These drives are read-only drives.
You can access data from them but cannot use them to write
data onto a CD.
A button on the front of the drive opens a tray on which you
insert a CD. You push the button to close the tray, so you can
use the disc's contents. Laserdisc drives, still used in some
settings, operate in much the same way. The tray must be opened
and the disc inserted before a laser can read the microscopic
patterns of data encoded on the surface of the disc.
Compact Discs & Digital Video Discs
Compact Disks, or CD’s capacity: A standard
disc can hold 650 MB & newer kinds can
store 700 MB
Digital Video Discs, or DVD’s, have larger
storage and holds at least seven times more
info that CD’s.
Review
Key Terms:
storage device
Basic Input/Output System (BIOS)
file
memory
hard drive
floppy disk drive
CD-ROM drive
primary storage
secondary storage
archival storage
read-only device
read/write device
sequential storage device
random access storage device
optical storage device
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