2.1 CD Writeables.
When you record a CD in a CD-writer on your home computer the laser in the drive doesn't create bumps on the actual CD. The disks that are used are different than the CDs that are pressed.
The CD-R disk has an extra layer compared with the pressed disk, in-between the polycarbonate plastic layer and the aluminium layer there is an extra layer of dye. When the CD is recorded the laser changes the colour of the dye, when the disk is unwritten the dye is transparent, but the laser changes the colour, making a dark, non-reflective spot. .
The CD writing drive has 2 lasers compared with just the one on a normal CD drive. It has a write laser and a read laser, the write laser is more powerful than the read laser, this makes it able to alter the dye layer of the disk, as the read laser is less powerful it will not alter the dye when it is read in any other CD drive. To record the data, the writer simply turns the write laser on and off in synch with the pattern of 1s and 0s. The laser darkens the material to encode a 0 and leaves it translucent to encode a 1.
Most CD burners can create CDs at multiple speeds. At 1x speed, the CD spins at about the same rate as it does when the player is reading it. This means it would take you about 60 minutes to record 60 minutes of music. At 2x speed, it would take you about half an hour to record 60 minutes, and so on. For faster burning speeds, you need more advanced laser-control systems and faster connections to the computer.
The main advantage of CD-R discs is that they work in almost all CD players and CD-ROMS, In addition to this wide compatibility, CD-R's are inexpensive and easily available. The main drawback of the format is that you can't reuse these discs.
2.2 CD Re-Writeables.
If the CD drive is re-writeable then this drawback is overcome, although the speeds are slower at re-writing a disk and the disks themselves are more expensive.
It used punch cards to input and output data; registers served as memory storage. ... These computers used random access memory, or RAM, to store programs and for data storage. ... The first generation of computers; namely, the ENIAC, EDVAC, and UNIVAC, all used vacuum tubes to represent data. ...
