I/O Devices

I/O Drives or Input/Output drives are those other mediums for reading and storing data besides your hard drive.  Examples of I/O Drives are CD/DVD-ROM/RW, Floppy, and USB Flash drives.  These drives allow you to store and read data from external and mobile sources, allowing you to more easily move the data.

 

 

 

This is a standard desktop DVD-RW drive. It uses the same concept of "burning" that a CD-RW drive does, just on a different type of disc; one that can hold much more information.

 

 

 

A much smaller version of its desktop counterpart, the laptop DVD-RW's still allow the user to burn DVDs, in a much smaller package.

 

 

 

This is a USB flash drive, they are most commonly used for the quick movement of files. Thumb drives allow you to move multiple GB's of data without having to waste media (such as CD-Rs or DVD-Rs) or go through network means.

 

How does a CD Drive Work?

To understand how CD's work you must first understand what makes up the actual CD. A stamped CD (a purchased music CD) contains a layer of plastic that has bumps imprinted into it. Over the layer of plastic is laid a layer of aluminum. This layer of aluminum makes the bumps and lands reflective and allows the whole CD reading process to take place. The laser reflects off of the aluminum surface and is read by an optical pickup. As you can see below, the bump and land areas make the laser reflect differently and thus give us the various bits of input for the computer.

Laser Hitting a Bump
       

 

Laser Hitting a Land Area

 

Receiving the laser reflection by the Optical Pickup is interpreted as a bit and is then sent off to the computer for further interpretation.

Continuing on with the makeup of a CD, acrylic is laid over the aluminum to protect it and finally the label is placed on top. It is important to note that the bumps are laid out around the disc starting from the center and moving outward around the disc. This allows various physical size discs to be used each storing different sizes of data.

A CD-R is slightly different only in physical makeup. A CD-R has a layer of plastic that is solid (no bumps), then a layer of dye, then a layer of aluminum, a layer of acrylic, and finally the label. The dye layer is darkened in the "burning" process. The laser then reads these darkened sections as bumps on the CD and interprets the information.