Idiot is an esolang created by User:None1, it is very stupid, but it can still write a cat program and a Truth Machine.
It uses an accumulator.
If character is empty, then the command is executed no matter what, otherwise it is executed if and only if the accumulator equals to the ASCII value of the character.
There are 3 commands, i, o and t.
i reads a character and stores its ASCII value into the accumulator.
o outputs the accumulator as a character.
t terminates the program, the program is executed all over again if it doesn't execute the t command.
Truth Machine (Needs non-interactive input)
i 0 ot o