Every information transmission system created by human beings is based on symbols: sign language, spoken language, written language, light signals, radio or other signals. To ensure that a message is completely understood, the meaning of each sign or symbol must be defined.
Language is the earliest and most important symbol system used by human beings. It enables mutual understanding, planning and anticipatory action.
Images were the early forerunners of written language: humans expressed themselves through images painted on caves and rocks long before they learned to write.
The oldest known systems of writing were created in Mesopotamia, Egypt and China. They emerged from pictorial symbols.
Number systems are even older than writing systems. Numbers were recorded in counting systems by using pebbles, clay balls or notches made in wood, bones or clay. Specific natural numerical units (fingers, hands, toes) were frequently given special symbols: 5, 10, 100... However, human beings were unable to do arithmetic calculations with these early numbers.