Abstract
The invention of writing more than 6,000 years in Mesopotamia is a recent phenomenon in human history. In the few million years that preceded this event, knowledge was passed on from generation to generation by oral tradition. Writing was a huge factor in accelerating civilization and transferring knowledge by enabling us to externalize our thoughts first on stone, parchment, then paper, and finally by digitizing and recording them on optical disks and computer servers. These media act as a kind of external memory that extends the storage capacity of our brain. This external memory can be accessed on demand, made permanent, changed in a multitude of ways, sent to others, used as a basis for mass communication orally or electronically, and distributed through print, analog, or digital media. The purpose of this chapter is to broaden our understanding of knowledge representation through organized systems of symbols, to present these systems, and to describe how they are used to understand, communicate, and solve problems.