A certain teaching machine developed at this laboratory has been named PLATO, standing for „Programmed Logic for Automatic Teaching Operations“.
It is a device for teaching a number of students individually by means of a single, central, high-speed, general-purpose digital computer, in this case the lLLIAC, the University of Illinois automatic computer. The general structure of PLATO is indicated in Fig. 1. For simplicity, only one student is represented in the diagram. The central element of PLATO is the high-speed digital computer.
Each student communicates with the computer by means of his own keyset, which can be provided with up to 64 keys representing a full complement of alphanumeric characters. When asked to answer questions posed to him by the machine, the student’s answers may thus take such varied forms as numerals, algebraic expressions, and words or phrases.
Special keys enable the student to control the presentation of material to him by the machine. The machine communicates with each student by means of closed-circuit-television. Material is presented in two different ways:
(1) The machine presents static textual material by commanding an electronic switch to connect the video output of the appropriate slide to the appropriate student’s display.
(2) Dynamic non-textual material, or material furnished in the course of instruction (such as student answers), is written by the machine on the student’s TV display tube by means of an intervening buffer storage tube.
For multiple, student operations, a keyset, television display, and intermediate output buffer storage device are provided for each student. The central computer and slide selector, however, need not be duplicated; they serve all students on a time-shared basis.
It appears to be important in multiple-student operations, to require the condition that no student shall be aware of any other student’s existence. To meet this condition, we are requiring the computer to respond to any student’s request within 200 milliseconds.
The general logic by which instruction takes place is indicated by Fig. 2.
Textual material is presented on a sequence of slides. When the student has finished reading a given slide, he may proceed to the next slide by pushing the „continue“ button on his keyset. Similarly, if he desires to review material contained on a previous slide, he may do so by pushing „reverse“. On certain slides, questions are posed to the student. He cannot „continue“ beyond such a slide until he has successfully answered all the questions theron. As the student types in his answer, the machine displays it — character by character — in the space provided for the answer on the slide. As soon as the student indicates to the machine that he has completed his answer, the machine responds by indicating „OK“ or „NO“, depending on the correctness of the answer. The student may continue to punch in revised answers until the machine indicates that the answer is correct.
If the student indicates to the machine that he needs help in answering the question — by pushing the „help“ button — the machine jumps to a „HELP“ sequence appropriate to that question. In this sequence, further relevant textual material, if necessary, is presented, and the original question is broken up into a series of „easy“ subquestions, designed to lead the student stepwise to the solution of the main question. A student need not complete a help sequence. At any point in the help sequence, he may indicate to the machine his desire to be confronted once again with the original troublesome question by pushing the „aha“ button. As indicated in Fig. 2, failure to answer this question properly, leads to a return to the help sequence at the point it was broken off. In the case where a student should feel it necessary to ask for help for a question posed in the help sequence, the machine itself will provide him with the appropriate correct answer to that question. The important features of the machine are:
- The material is presented to every student in a standard, objective fashion.
- Each student may proceed at his own speed, seeking as much or little supplementary material as he wishes, subject to the boundary condition that he must solve successfully a prescribed sequence of problems.
- The machine keeps an accurate record of each „move“ the student makes. Thus at the end of an instruction period, the experimenter has at his disposal a print-out of how long the student spent on each page, what right and wrong answers were given and in what sequence, how long a problem took for solution, at what points help was requested, etc.
- The student knows as soon as he has worked the problem, whether his solution is correct or incorrect. In the latter case, the machine can indicate „NO“ without in any way revealing the correct solution.
- To test the versatility of the machine as well as the basic logic of the computer program, a number of instructional sequences have been prepared ranging from topics in mathematics (such as the elementary theory of congruences) to instruction in computer programming. To change machine instruction from one subject-matter to another requires only replacing slides in the slide selector and giving the computer an appropriate set of parameters.
A study using the machine to teach high school students the binary and other non-decimal number representations has been completed. Post-tests given the students participating in this study indicated that they had been able to learn from the machine. It also provided useful information on data-rates-considering the teaching system from the standpoint of an information processing system. Studies on teaching students computer programming are currently in progress.