So I was watching this (https://www.youtube.com/watch?v=WkIR23emsWY) by technology connections and I just realized that I have no idea how CDs work. The video is about how some CD players can read audio of a CD where the data is just copied directly onto a CD with a computer whereas older players only had hardware compatible with CDs formatted as …. digital audio?
I was trying to figure it out on wikipedia, how is a commercial CD you’d buy in a store different from a CD with files copies onto it?
I remember my dad used to use a burning tool to make images. Why are they called images? How is an image different from a CD?
Why are some CDs readable and writable but some aren’t?
In: Technology
Commercial CDs are physically stamped. There is a long groove of high points and low points (lands and pits) that spiral from the center of the disk to the edge that are interpreted as 1s and 0s based on whether or not a laser shone on them reflects back to a sensor or not. Writeable optical media is ink-based. A new CD-R is shiny. When you write data to the CD, the ink is “burned” to make non-reflective spots. So instead, shiny/not shiny are your 1s and 0s. Eventually, the ink will fade. This is why you should back up any optical media you may have created.
(Fun sidenote: CD players used a red laser. If we want to pack more data on the disc, we need the lands and pits to be closer together. This means we need a shorter wavelength of light to read them. In the visible spectrum we all know as ROYGBIV, red is a longer wavelength. Blue is shorter. Hence. Blu-ray.)
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