10. Backing Storage: Optical and Solid State

 

 

Optical Drives

These drives use Lasers (light) to read information from disks and in some cases write information to disks.

There are two main types, CD and DVD disks. They are used more and more, as increasingly information (music, films etc, software) is only available on this type of media.

 

1. Compact Disk - Read Only Memory (CD-ROM)

CD-ROM drives use a combination of lasers and sensors to read the data stored on the surface of the disks.

 

CD-ROMs are read-only devices. They can hold in the region of 700 megabytes of data.	Like hard disk drives, CD drives use direct/random access to read data.
Movie: 17. Compact Disks

 

 

 

 

 

 

2. Digital Versatile Disk - Read Only Memory (DVD ROM)

A DVD-ROM drive is similar to a CD-ROM drive in that it uses a combination of lasers and sensors to read the data.

DVD ROMs are also read only.

 

Movie: 18. Digital Versatile Disks	Again, DVD players use direct/random access to read data.

 

 

 

 

 

 

Drives can be external and plug separately into the computer system like the one shown. Others can are built into the computer system.

 

 

 

 

 

More Information

a. What they are used for?

CD	Mostly used for music and other data files (e.g photos), because they can played on almost any CD player.
DVD	DVD's are mainly used for storing movies because the files needed to encode a movie are very large indeed and are measured in gigabytes.

 

b. Different versions of CD's and DVD's

CD		DVD
	CD-Recordable (CD-R) This is a CD similar to a CD-ROM. The difference is you can store data on the CD-R. Standard CD-R disks hold 700 megabytes.		DVD-Recordable (DVD-R/DVD+R) These are DVD disks that you can write to by using a DVD-Rewriter drive.
Using a laser and special dye in the disk a CD-Rewriter or DVD-Rewriter drive can store your data on the CD/DVD. Once the data has been burned on to the disk you cannot change it, it is read only.
CD-Rewriteable (CD-RW) Like CD-R, these are compact disks on which you can store data using a CD Rewriter drive. The main difference is that you can change the data later on if you want to, just as you can on a hard disk.		DVD-Rewriteable (DVD-RW/DVD+RW) These are DVD disks that you can store data on over and over again, with a DVD-Rewriter drive. They use similar laser technology to CD-RW whereby the reflective properties of the disk are altered to represent binary numbers.
Movie: 19/20. Read Write Disks   14 and 15 in Kickin Technology Series: . CD Read Write (CD-RW) and DVD Read Write (DVD-RW) Store your own work on these types.

 

c. Storage Capacity of different versions of DVD's

Choose the correct to type to store your work
Single-sided/single-layer	4.7 gigabytes of data – over 2 hours of video
Single-sided/dual-layer	8.5 gigabytes of data – about 4 hours of video
Double-sided/single-layer	9.4 gigabytes of data – about 4.5 hours of video
Double-sided/mixed-layer	13.24 gigabytes of data – about 6.5 hours of video
Double-sided/dual-layer	17 gigabytes of data – over 8 hours of video

 

 

 

Solid State Storage Devices

In contrast to magnetic and optical forms of backing storage, these devices have no moving parts and so are called 'solid state'. Instead, they use a special kind of programmable ROM memory chip on which data is stored. Very different to usual memory, these kind of chip remember the data even when the power has been turned off.

 

1. USB Flash Drives

Universal Serial Bus (USB) is a type of socket or port in computer systems that allow USB type devices to connect to it. One of which is the USB Flash Drive - sometimes called pen drive.

USB Flash drives come in various sizes from 16 MB up to and over 4GB. They are very useful and a simple way way of backing up and transporting data. Because of the USB connection they will work on any computer with a USB port and have really replaced floppy discs as a method of moving files from one computer system to another.

 

 

 

2. Memory Cards

Like USB Flash drives, these solid state devices come in various sizes, from 64MB to over 2GB. They connect differently and need a card reader to 'read' their contents.

Commonly, they are used in digital cameras to store photographs and are similar to SIM cards used in phones.

 

 

 

 

 

 

 

What you have to do!

Watch the videos above and in your Word document or your Brain complete the following exercises.

1. What is the typical capacity of a CD-ROM?

2. What are CD-ROM's used for?

3. What is the typical capacity of a DVD-ROM?

4. Why are DVD-ROM's used to store video?

5. Why are USB Flash drives so popular?

 

 

What you should be able to do!

1. Provide examples of Optical Type Backing Storage devices.

2. Explain the difference between CD/DVD-ROM and CD/DVD-RW disks

3. Provide examples of what you use each type of disk for and explain why?

4. Provide examples of Solid State storage devices.

 

Continue to 11. Comparing different backing storage formats