Many programmes available form and are relatively to buy. Films are usually more expensive and there is the additional price of the machine required to present them. These tend to simpler of the branching variety and may cost over £200. Much machines, costing only a few pounds, can be bought for presenting linear programmes, which are either published on rolls of paper or can be made up by the teacher. However, the general principles of programmed learning can be followed quite simply with home-made equipment, which need be no more elaborate than a large envelope. If about three-quarters of the opening of the envelope is cut away to a depth of about one inch on the left-hand side, a linear programme can be presented on foolscap paper by simply drawing it slowly out of the envelope. The frame revealed in the cut-out on the left, while the answer is covered by the protruding portion of the envelope on the right. When the paper is pulled out further to reveal the next frame, the answer to the previous one also comes into view and the student can check his response immedi- ately. Again, it is a question of flexibility and imagination, and no one eager to use programmed learning will find cost a deterrent.