CD-ROMs
Write once, read many times
A rewritable version (CD-RW) is available, but not in common use
Information is “written” by burning tiny holes in the disk surface with a laser
The hole pattern is read by a laser and inter- preted as the bits comprising the data
Can store 600-700 megabytes of data; about 300,000 pages of double-spaced text, or more than an hour of high fidelity sound