2 Here Come Multimedia: Its Meaning
2.1 Picture (or Image)
Traditional teaching/learning materials are texts. In the origin/base of a text there are pictures. But the text is not such a kind of thing that re-presents the pictures.
To reconstruct pictures from a text is a jump - a blind jump. Indeed, those who can, more or less, read a text are those who already has the pictures from which the text originates. ( It is a tough work to describe this coffee cup in the form of text. And, even if I could finish it, nobody can re-presents this coffee cup from the text. )
If it is possible to serve pictures directly in the form of picture, that is the best.