Computer Storage Devices

Principles of Information Technology

Lytle High School

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Disk Drives, Hard Drives and Data Storage

Welcome to this lesson on computer storage devices.

There is much to know that the average computer user may not have learned.

If you wish to use computers more effectively, read on.

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External Storage Random Access Memory is only temporary. Computer

memory is cleared or erased when the computer loses it’s power

It is for this reason that documents or projects you create be saved on disk.

Disk storage is permanent. Any information saved on disk is recorded until needed at a later time and is not erased until you decide to erase it.

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Types of Disk Storage

While there are many types of data storage devices for computers, we will discuss the most common ones first.

Today’s computers share some common storage devices.

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3.5” Disk Drive

Hard Drive

CD-ROM drive

Recorded Information

Today, information is recorded in a variety of ways. In a USB drive, information is recorded on a microchip. On a CD or DVD, the data bits are etched into the special coating of the CD or DVD.

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On a hard drive, data is recorded with microscopic magnetic spots.

How is Data Stored?

Before a diskette or hard drive can be used, it must be FORMATTED.

The format process is a special initialization process. If a disk is not formatted to the computer’s specifications, it cannot be used.

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Tracks and Sectors

The format process creates TRACKS and SECTORS.

These sectors and tracks are the storage locations where data is actually recorded or saved.

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Recording Computer Data

As mentioned earlier, Information is recorded on disk. Data is recorded with little magnetic impulses. Hard Drives are precision instruments. As the disk surface

spins, the Read-Write head records the information.

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Random bits are put in their proper byte sequence by the read-write head.

Recording Computer Data

If the computer gets bumped hard enough, the Read-Write head can bump the surface of the disk. This is known as a Head Crash and all the data on the disk surface is scrambled and lost. The surface of the disk is scratched and ruined, and the hard drive itself must be replaced. All saved data is lost.

The Read-Write heads are so close to the surface of the disk, extreme care must be taken not to bump the computer when it is in operation.

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Units of Measure

The terms used to measure disk storage capacity are the same terms already learned in a previous lesson.

Remember them? They are the same terms used to measure computer memory or RAM.

KILOBYTE is equal to one thousand bytes of data.

MEGABYTE is equal to a million bytes or characters of data.

Today’s hard drives store GIGABYTES of data. A GIGABYTE is equal to one billion characters of data.

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The Hard Drive

Computers today usually have three storage devices.

The internal HARD DRIVE unit is a high capacity storage device.

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The Hard Drive

Today’s HARD DRIVES are capable of holding millions of times the capacity of a single 3.5” diskette.

The computers purchased today usually come with 100, or 200 Gigabyte hard drives.

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Disk Drives

Hard Drives are found inside the computer cabinet.

There are no diskettes to insert or remove.

All information is permanently stored until you, the user, decide to delete it.

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Hard Drives

Hard drives are installed in the computer cabinet. With other disk drives in the computer, the hard drive is identified by a letter.

The letter C: is assigned to the hard drive. The C:Drive is the primary or default storage device for the computer.

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The Importance of the Hard Drive

All of today’s computers have large hard drives in them.

When you first turn on the computer, they power up, or BOOT UP, with the Operating System found on the hard drive.

WINDOWS 2000 or WINDOWS XP is the operating system needed by the computer to run. Without it, the computer cannot be used.

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Floppy Diskettes

These floppy diskettes are now obsolete and no longer being installed in computers. However, the 3.5” diskette is still used, but is slowly fading. Notice the 8” Floppy Disk. This is one of the first storage devices created for the computer.

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The 3.5” Disk Drive

While hard drives can store billions of bytes of data, 3.5” diskettes are much more limited in there storage capacity.

The capacity of a 3.5” diskette is 1.44 Megabytes.

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Disk Drives

3.5” Disk Drive

The 3.5” disk drive is located in the computer cabinet.

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3.5” Diskette

Remember, information once saved, is permanently stored and is not deleted until you the computer user decide to delete it.

Disk Care

While 3.5” diskettes are pretty durable, care must be taken so they are not damaged.

– Keep from extreme heat– Keep from extreme cold– Keep away from magnets– Keep from getting damp or wet– Keep from getting smashed– Do not touch the recording media

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The CD-ROM Drive

Another common storage device is the CD-ROM drive.

Compact Disks are capable of storing 600 to 700 megabytes of data.

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Disk Drives and Drive Letters

The letters A: and B: are reserved and assigned to the 3.5” disk drives.

The computer assigns the letter C: to the hard drive.

The Compact Disk or CD player is usually assigned the letters D: or E:.

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As mentioned earlier, the computer knows its disk drives by assigning a letter to each storage device.

Keeping Track of Saved Files

When you save information on disk, it is up to you, as the computer user, to tell the computer where you want your data saved.

Do you wish to save your document on the A:Drive, or C:Drive?

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Saving Data

Many of today’s Compact Disk Drives allow you to record information on a blank CD.

Today, computers come with CD-ROM drives that allow you record or save your documents or other files on a CD-ROM, or the D:Drive.

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Computers and Disk Drives

Always be aware of where information is saved.

If care is not taken, you will not know where your data or information is stored.

It will be lost, and you will not be able to locate and open your file when it is needed.

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Other Storage Devices

Computers have RAM. Ram also has a storage capacity.

Can you tell how much information can be stored in this SD-RAM?

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Zip Disks

While 3.5” diskettes have a 1.44 Megabyte storage capacity, other forms of storage have been developed.

About the same physical size as a 3.5“ diskette, the ZIP Drive uses special disks that can hold 100 – 200 MB of data.

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Other Storage Devices

Compact Disks hold about 5 times more than a Zip Disk. They can store between 550-650 Megabytes of data on each CD.

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DVD Storage

Today, computers come with DVD storage drives. Similar to a CD storage drive. They have a much larger storage capacity. They are used to store 4.7 Gigabytes or 8.5 Gigabytes of information.

This is the reason they are used to record and view movies that are 2 – 4 hours long. This amount of storage capacity is just not available on a regular CD Drive.

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Tape Drives

Tape drives use special tape cartridges that look similar to cassettes, but are physically smaller in size.

Tape drives come in a variety of sizes and shapes. They are used for Backing Up large amounts of important hard drive data, and can store from 200 to 300 Gigabytes of data.

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Flash Memory

There are various types of storage available for other electronic devices.

Digital Cameras as well as certain copy and fax machines use special memory adapters.

Additional storage devices are also available for Lap Top computers.

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Flash Memory

Other Storage Devices

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Flash Media Cards come in a variety of sizes, and are used in MP-3 players, digital cameras, printers, etc.

Thumb or USB Drives come in a variety of sizes, and plug into the computer’s USB port. They come in a variety of storage capacity and sizes.

Flash Memory

Can you tell how much data can be stored in these Flash Memory cards?

This type of memory card is used in many of today’s digital cameras.

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In Conclusion

Disk drive storage can be confusing to those who do not familiar with how things work. Take the time you need to learn about storage devices and how to save and retrieve files.

The information you save on disk is important to you. Know where it is saved and know how to get it back.

Good luck on your quest for better understanding.

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In Conclusion

Now that you have completed this lesson on data storage, prepare to share what you have learned with others.