compact disc (CD)

A comparison between an magentic audio tape and a Compact Disc (CD) highlights several key aspects of the shift from mechanical and analogue products to digital.
Firstly a magentic audio tape is a linear technology. It can only be read in a specific sequence. For example if you were looking for a favourite music track on an audio tape you would have to wind the tape in sequence forward or backwards to the song. In contrast, a CD is nonlinear. To find your favourite track on a CD, you can skip songs and go directly to the song of your choice.
Secondly, an audio tape is read by coming into direct contact with a ‘recording head’ or ‘reading head’. The magnetic tape runs across the head and is then interpreted into audio. This is more obvious if we consider the old plastic records where a needle literally sat in the grooves on the surface of the round disc as it rotated. In contrast, a CD is read by a laser and no direct contact is made between the laser. The laser is like a finely tuned torchlight scanned across the notches in the CD and bouncing the light to be picked up by a light reader. The advantage here is that direct contact wears out the parts in contact, whereas the non-contact does not wear out the laser.