PI is a method for structuring and presenting information. The development of programs usually employs a systematic approach, including a statement of terminal objectives, task analysis to determine the type of mental/physical activity required by the objective, and evaluation of learning referenced to those objectives.
Most programs are also characterized by a structure that includes some sequence which implies a progressive development of ideas which successively approximates the behavior stated in the objective, along with some form of active response to some form of question appearing after each unit of information. It also includes feedback or confirmation of the correctness or incorrectness of the response.
Another general characteristic of programs is evaluation or learner verification and revision: a tenet of programming which requires the programmer to try out the program with a group of users, similar to those for whom the program is intended, and then to revise the program based upon the feedback until it reaches a predictable level of effectiveness. Traditionally, the accepted success criteria have been a 90% level of performance with 90% of the users 90% of the time. The design of computer-assisted instruction packages also works this way.