TinyBF

tinyBF is a brainfuck equivalent with only 4 characters. It's a variant of RISBF and was created by Michael Gianfreda, Nov. 6, 2014. tinyBF programs are smaller than RISBF's. The motivation for creating tinyBF was to have four 2-bit commands in one byte of program memory.

Output
Since switching the direction twice doesn't change anything, we can use this as the output function: ==

Input
The brainfuck endless loop [] can be used as input function: |=| if switch is positive, =|=| if switch is negative.

Hello World
++++++++|>++++|>++>+++>+++>+=>>>>+|=>+>+>=+=>>+|=>|>+|=>>==>=+++== =+++++++====+++==>>===>+==>===+++===++++++==++++++++===>>+==>++==

Reverse input
+|>|=|=|>+=|+===>+|

External resources

 * A tiny (1476 Bytes) brainfuck-to-tinyBF translator and interpreter in Javascript