CRT terminals were a thing by then. Spacewar!, for example, used a CRT in 1962, and the original PLATO paper from 1961 (https://ieeexplore.ieee.org/abstract/doc

CRT terminals were a thing by then. Spacewar!, for example, used a CRT in 1962, and the original PLATO paper from 1961 (https://ieeexplore.ieee.org/abstract/document/4322215 https://ieeexplore.ieee.org/abstract/document/4322215) says: > The computer communicates to each student by closed circuit television. It selects slides and writes or erases sentences and diagrams on a storage tube. These two outputs are superimposed and displayed on the student's television screen. Not only are textual materials presented to each student at a rate determined by that student, but the computer frequently poses questions. (See also https://core.ac.uk/download/pdf/4812121.pdf https://core.ac.uk/download/pdf/4812121.pdf p36 for more details.) Also, it doesn't need to be a CRT. Plasma displays were developed for PLATO IV because, to quote the 1966 paper (https://dl.acm.org/doi/pdf/10.1145/1464291.1464349 https://dl.acm.org/doi/pdf/10.1145/1464291.1464349): > Display technology, however, has not kept pace with these advances. The TV-storage tube displays, of course, perform well in the PLATO system, and other CRT devices are used successfully in information retrieval systems. However, no display device is now available that performs well, and is sufficiently inexpensive for use in these large systems. This make it possible to read the 1967 Final Report of the BASIC (https://files.eric.ed.gov/fulltext/ED024602.pdf https://files.eric.ed.gov/fulltext/ED024602.pdf) in context. When they write: > Our experience does not include what is usually called CAI. While more elaborate CAI systems using fancy terminals (including TV-type presentations) could be attached to a general purpose computer system such as ours, the terminal costs would be much greater than those for teletype machines. the "CAI" there means "computer-aided instruction", and is, I think, mean to include PLATO with its more advanced displays.