In the 1979-1981 time-frame, floppy disks were quite expensive, yet cassette tapes were a dime a dozen. Dann McCreary had the idea of putting an entire disk on tape. Thus Tape-O-Disk was born. However, after the prices of floppy disks came down to a level where everyone could afford them, the program all but disappeared until re-discovered by Apple ][ collector Antoine Vignau. When Antoine replied to an correspondence inquqiry by Dann, he received back one of the most insightful letters giving full perspective on the era in computing and the software industry as a whole of the time. In the letter he talks about a variety of topics including where the sales came from, how he paid for advertising and many other interesting pieces of information from the world of 1980 software as seen by Dann McCreary.
You can read the letter in full at:
The page also contains the cassette of the Disk-O-Tape program as long as all of the related materials to the program.