Computer aided learning, or CAL, is the use of computer based programs intended to take the place of traditional classroom based teaching (particularly lectures). Under CAL, the lecture is replaced with computer based programs the student uses to teach themselves the material.
There are a few problems with CAL. First, no actual instruction is given. Students are required to read the material (passages, graphs, explanations of equations, etc.) and derive knowledge from it on their own. One problem which arises is that a student cannot ask questions of the CAL program. Therefore, if a problem arises, there is no secondary place to go within the program. Students must act on their own to find the answers that they need.
That being said, CAL (when constructed properly) consists of different types of educational based audio-visuals. This can help some students who vary in learning styles (given the program consists of actual text, visual images, and audio files.