Magnetic Storage: Hard Drive
A hard drive is computer hardware that holds and spins a magnetic or optical disk. Data is stored on the disk's tracks. The heads read and write information off of the disk. Memory is there whether the power is on or off. It takes longer to read than other storage mechanisms. Cheapest per gigabyte at approximately $0.03.
Optical Storage: CD, DVD, Blu-ray Disc
A compact disc is a thin, circular disc made of metal and plastic. It has three layers. The computer reads the CD by beginning at the center and spiraling out. A laser hits the bumps and flats on a CD and reflects them back to the computer which reads them as binary code. Binary code is read in 1's and 0's. DVDs hold 7 times as much info as a CD and Blu-ray discs hold 40 times more info than a CD. It varies in cost. For a CD, $0.25 per gigabyte. For a DVD, $0.04 per gigabyte. Finally, for a Blu-ray disc, $0.07 per gigabyte.
Flash storage is a small storage medium often used to store data of photos, music, text, video, etc. It remembers info when the power is off. It can be erased and rewritten. It has a source, drain, and a gate. The gate controls the flow of electricity which determines readings of 1's and 0's. It is faster than a disk drive. It costs the most at approximately $1.50 to $4.00 per gigabyte.