Image: Maria Bibikova, iStockphoto
About This QuizCompact discs are a popular storage device for both music and computer files. But how much do you really know about them? Take our quiz to find out!
How many megabytes (MB) of data can a compact disc hold?
A CD can hold a little over 783 megabytes of data, or about 74 minutes of music.
1 billion megabytes
What are CDs made of, primarily?
The primary material in a compact disc is clear polycarbonate plastic.
How are data physically arranged on a compact disc?
In a series of dashes and dots, similar to Morse code
In a zig-zagging trail of microscopic colored dots
In a single spiral track of tiny bumps
Information on a CD is arranged in a series of bumps that begins at the center of the disc and spirals out to the edge.
How long would the series of bumps on a CD be if it were in a straight line?
The bumps would only be .5 microns wide, but the string would extend nearly 3.5 miles long!
What keeps the laser in a CD player in line with the data track?
The tracking system
A tracking system aligns the laser in a CD player to a CD's data track.
The linear actuator
The articulated gimbal
What does EFM stand for?
Electric force motor
Encoded field magnet
Data on CDs is encoded with eight-fourteen modulation (EFM), which converts 8-bit bytes into 14 bits.
What kind of information is stored on compact discs?
Compact discs store information as a series of 1s and 0s, also known as digital information.
What's the term for the non-sequential storage method CDs use?
CDs use interleaving to store data non-sequentially. CD drives read the data and then un-interleaves the information to make sense of it all.
What reflective material coats the polycarbonate plastic on a CD, making it readable by CD drives?
CDs have a thin coating of aluminum behind the polycarbonate plastic. The CD drive's laser reflects off the aluminum and is detected by a sensor.
As a drive reads a CD and moves from the center to the outer edge of the disc, what happens to the CD's spinning speed?
The CD drive has to spin the CD slower as the laser moves outward. That's because the bumps on the outer edge move faster than the ones in the inner edge -- they cover a greater distance in the same amount of time as the inner bumps.
It stays the same
Maria Bibikova, iStockphoto