Jackie [Dobrovolny, 30 Apr 96] asks for more detail on the media forms I referred to. Fair point.
There are so many forms of IT use in education it is difficult to try and shoe-horn them into a few basic types, and four are really too few. But for the argument being made here I hope they are sufficient, because they distinguish the different resourcing implications quite effectively.
CAL refers to any form of computer-based teaching program, i.e., a stand-alone, interactive program which responds to student input and structures their activity. It might be a tutorial program working towards an explicit learning objective, a simulation of a system the learner can interact with and explore the behavior of, a microworld (like LOGO), even (stretching a point) an information resource like a multimedia encyclopedia. It is developed by the teacher in advance for unlimited numbers of learners to use in stand-alone, self-support mode, practice to the fore.
Audio-graphics is for on-line synchronous conferencing. Students work in a small group (six?) with a co-ordinator/moderator all communicating via audio (telephone line or real audio on the net, or audio-conferencing device) and via datalines which allow all of them to be looking at the same screen on their own computers, or manipulating each others' screens. The screen may show a graphic, or someone's essay, or be running a simulation, so the talk is about the practice being displayed on the screen. Little advance preparation by the tutor, high staff-student ratio, group work, articulation and practice to the fore.
Computer-mediated conferencing is the asynchronous text-only version of this. No need for two lines or high bandwidth. Students and tutors do what we are doing here, though using software that supports the working structure a bit more. Little advance preparation by tutor, variable time depending on how much reading of student input they do and how much input of their own, group work, some may be more active than others, articulation and reflection to the fore, (attending to the fore for those who do not contribute, only 'lurk').
Interactive computer-marked assessment derives from our practice at the Open University of issuing "computer-marked assignments" for many years. This was before our students had computers and networking, and used multiple choice tests with optical character readers to mark assignments sent in from thousands of students. Something similar(ish) can now be done with interactive on-line programs. The test would NOT use MCQ's (dreadful things), but would use open-ended questions with answer-matching, or calculations, or graphic input to identify a point on a curve--all sorts of possibilities. (I came across a nice one in Australia last year where students had to type in the text of a French speaker--difficult comprehension problem for them, but easily checked by a computer). Could be done as formative test off-line, or summative test on-line on a specific date. Advance preparation needed, but could be re-used many times if questions are generated by program, individual off-line work by student with as much practice as they wish, practice to the fore.
I hope that helps to clarify what I meant. Normally I would characterize, say. tutorials and simulations as different kinds of learning medium, but for the purpose of this analysis of the resource implications, they are more similar than not.