While new characters can be easily coined by writing on paper, they are difficult to represent on a computer – they must generally be represented as a picture, rather than as text – which presents a significant barrier to their use or widespread adoption. Compare this with the use of <answer>symbols</answer> as names in 20th century musical albums such as Led Zeppelin IV (1971) and Love Symbol Album (1993); an album cover may potentially contain any graphics, but in writing and other computation these <answer>symbols</answer> are difficult to use.
What has their been a prominent supply of in the 20th century?
symbols