HELLSCHRIBER
A mode from before computers it writes characters vertically on paper tape. An ideal mode for digital, it saves paper tape and modern equipment has no drift problems.
Note the screen divided into strips of 'paper tape' and the use of two rows of characters to overcome phase errors. Old timers would have to adjust constantly for this. Activity can be found around 14.063 MHZ it sounds like a flock of geese flying over.
PSK31
A superb narrow band high accuracy RTTY developed for the digital age by G3PLX.
For real action try Zakanaka running two receive windows at once PSK31 Activity can be found around 14.070 MHz.
RTTY
Radio Teleprinter is an old mechanical mode which is also ideal for computer use.
BAUDOT
A fairly easy mode to write a program to utilize a microprocessor to decode and generate.
CW Morse Code
Morse code the original digital code for manual reading can be read and generated by computer.
dah dah di di dit
di di di dah dah
Another fairly easy mode to program a microprocessor for send and receive. Also as a tutor for learning the code.
There is nothing down here