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Brainfuck

Brainfuck is a computer with an infinite tape for memory.

It runs a tiny instruction set with eight commads.

Theoretically Turing complete.

Note 'computer' here is used as the lowest form it would make sense to understand at.

It is most commonly used as an interpreted language.

Instructions

< and > Moves left/right along the tape.
+ and - In/decrements the pointed value on the tape.
, and . In/outputs the pointed value on the tape.
[ Jump right to the matching ] if the pointed value is 0.
] Jump left to the matching [ if the pointed value is not 0.

Tape memory

Brainfuck's memory is desribed as a 'tape', an infinite sequence of cells.

There are many variants of this tape.

Each cell is a byte (not always an octet!), wrapping around on overflow. "computer's memory"
Each cell is an integer (−∞<n<+∞). "list of numbers"

Traversal in both directions. (+vs & −ve indexes)
Traversal only to the right of the initial cell. (only +ve indexes)

Input and output

Input will block if there is no buffered data.

Upon reaching the EOF there are variations:

Nothing happens. The value in the cell is not modified.
A value of 0 is written to the cell.
A value of -1 is written to the cell. (with byte-cells, this wraps to the max value)

Common virtual machine quirks

It is common for a virtual machine to buffer input, only sending it upon receiving a newline.

Newlines are often normalised to a line-feed (LF, '\n') upon input.

Textual format

Brainfuck code files use a file extension of `bf`.

Commands are represented by their symbols, any other characters are ignored.

'!' is sometimes used to seperate code (left) from pre-buffered input (right).

'#' is sometimes used to print debug info on the current state of the computer.

Extensions

There are many, many extensions to brainfuck.

A table of extensions.

Often these raise it to a programming language, not a computer.

Beware the 'equivalents', where people have only replaced the symbols, without modification.

Elsewhere

https://esolangs.org/wiki/brainfuck