Until very recently, computer assisted instruction was a sophisticated area of research that involved very large computer systems. Often the computer was centrally based at a university or technical institute and accessible via remote terminals linked to the computer by a telephone connection. The capital cost of such equipment is very high and only within reach of large institutions. Even when a central computer system is readily available, it is very expensive to provide and connect remote terminals. Despite research that shows convincingly that computers are effective teaching aids in special education, the complexity and cost of equipment discouraged the development of computer assisted instruction.