The earliest CBI systems emulated programmed instruction texts, which employed frames as their basic unit of structure. A frame in programmed instruction may convey information by providing definitions, presenting rules, giving examples, explaining concepts, and suggesting techniques for solving problems (Burke, 1982). Frames may also contain questions that a student must answer or may contain solutions that a student uses to check his or her answers. The earliest CAI systems, particularly those using teletypes, were very limited in the ways in which they could interact with students. These systems were capable of typing the text of the lesson onto a piece of paper. A student could read this text and could type responses, which the lesson program evaluated for correctness.
Because early CAI systems were capable only of presenting and accepting text, usually without much formatting, they were limited to a frame based architecture. Because text represents language, which is an element of discourse, such systems were capable of providing instruction. The effectiveness of this instruction was defined by the ability of the system both to discriminate between correct and incorrect student responses and to respond accordingly. The best systems also had the ability to discriminate among different types of errors and to provide a student with the guidance necessary to correct them.
CAI authoring systems, like PILOT, were developed around the frame based architectural model. Using such a language, an author not only could specify the text of instructions and questions, but could also control the flow of the lesson depending on how the student responded to each problem in the drill. CAI enhanced programmed instruction by contributing to it this notion of conditional execution, which is a typical characteristic of computer programs.
[ Index | Previous Paragraph | Next Paragraph ]