CDs and DVDs

1. CDs and DVDs • Are types of optical storage media that consists of a flat, round, portable disc made of metal plastic and lacquer. • Store software, data, digital photographs, movies, and music

2. Characteristics of CDs and DVDs • Are not magnetic media, instead they are optical media that store items such as data and instructions • Uses microscopic pits (indentations) and flat areas that are in the middle layer of the disc

3. How a CDs and DVDs are read • A high powered laser light creates the pits. • A lower powered laser lights reads items from the disc by deflecting light through the bottom of the disc, which is usually gold or silver • The reflected light is converted into a series of bits the computer can process • A land causes the light to reflect, which is read as binary digit 1. • Pits absorb the light; this absence of light is read as binary digit 0. • Items are commonly store items in a single track that spirals form the center to the outside edges of the disc

4. Care of CDs and DVDs • Never bend a disc; it may break • If a disc becomes warped or if its surface is scratched, the data on the disc may be unreadable • Exposing to extreme temperatures or humidity could cause them to warp. The ideal temperature is 50-70 degrees • Stacking discs, touching the undersides or exposing them to any type of contaminant may scratch it • Best place to store the CD or DVD is in the jewel box that it came in

5. CD-ROMs • Is used for storing data, instructions and information in addition to audio and video • Can only read the content on the discs, meaning that they cant be erased • A typical CD-ROM can hold from 650 MB to 1GB of data

6. Is a small data CD that stores up to one role of film using a jpg file format Picture CD usually is 1024x1536 pixels The cost of a picture CD is about 10 dollars per role of film Stores multiple rolls of film using the Image Pac or PCD Designed for commercial and professional users Resolutions ranging from 128x192 to 4096x6144 pixels Store images from 35mm film, negatives, slides and scanned items Picture CDs and Photo CDs

7. Multi session CD which user put there own information on to To be able to write on the CD-R you need a CD-R drive to burn the CD Has a speed of 40x or more CD-RW is a rewritable CD that can be erased. Is much like a floppy disc Only down fall is that the more it is erased the more faulty the CD becomes The CD-RW drive has a speed of 52x or more CD-Rs and CD-RWs

8. DVD stands for digital versatile disc or digital video disc Can store up from 4.7GB to 17 GB the storing capacity has more than enough to hold a telephone book containing every resident in the United States The goal of the DVD technology is to meet the needs for home entertainment, computer usage and business data DVD-ROM players can read up to speeds 48x or more Look just like the CD-ROM and sometimes are easily confused First involves making the disc denser by packing the pits closer together Second involves using two layers of pits. For this to work the lower layer of pits is semitransparent so the laser can be read through the upper level. This technique doubles the storage capacity of the disc Finally some discs are double sided and need to turn it over when you are done with the one side DVD-ROMs

9. DVD-ROM Storage Capacities