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Paradigm(s) imperative
Designed by Fernando Iazeolla
Appeared in 2015
Memory system tape-based
Dimensions one-dimensional
Computational class Turing complete
Major implementations bfng, (mirror site)
Influenced by Brainfuck, ReverseFuck
File extension(s) .bf

The title of this article may well be brainfuck-ng, due to typically being lowercased except, often, at the start of a sentence.

Brainfuck-ng is a powerful interpreter of a superset of brainfuck language. It is full compatible with brainfuck, and has in addition some enhancements.

Language overview

Brainfuck-ng operates on an array of memory cells, also referred to as the tape, each initially set to zero. There is a pointer, initially pointing to the first memory cell. The commands are:

Command Description
> Move the pointer to the right
< Move the pointer to the left
+ Increment the memory cell under the pointer
- Decrement the memory cell under the pointer
. Output the character signified by the cell at the pointer
, Input a character and store it in the cell at the pointer
[ Jump past the matching ] if the cell under the pointer is 0
] Jump back to the matching [ if the cell under the pointer is nonzero
( language extentions )
! output the integer signified by the cell at the pointer
? Input an integer and store it in the cell at the pointer
@ exit execution and return the value pointed by the last execution executed.

All characters other than ><+-.,[]!?@ should be considered comments and ignored.

If no input environment array is given, the environment array is initially an array of a fixed dimension with all cells septed to zero . The initial dimension depends on interpreter implementation.

Return value

Brainfuck-ng always return the value of the cell pointed by the last instruction executed.

bfng - The brainfuck-ng interpreter



brainfuck-ng v0.1

USAGE: bfng [options] [file]
valid options:
-i              --shell         interactive (shell mode)
-h              --help          show this help
-v              --version       prints brainfuck-ng version number
-s              --stdin         read bf prog from stdin
-d 'datum'      --data          set environment-array
-o              --out           print env-array to stdout after computation
-p              --print         same as -o but with newline added.
-r              --reversefuck   switch 'ReverseFuck' mode on.
-m size         --size          set the size (in bytes) of environment array (default is 32K).
-x 'prog'       --exec          gets & execute bf prog
-c              --cin           gets environment-array from stdin
-b  file        --xfile         gets bf prog from file
-a  file        --dfile         gets environment-array from file

interpreter's interactive commands

in shell interactive mode you can give brainfuck-ng interpreter the following command:

      :q     quit interpreter
      :h     print help summary
      :ks (yes|no)
             :ks  print  the  keep  state variable. :ks yes or :ks no set the
             keep state variable. The keep  state  variable  can  retain  the
             value of the environment-array between line input.
      :p     print the environment-array to stdout (added with \n endline).
      :r (yes|no)
             enable/disable/show reverse-fuck mode.
      :set datum
             set the environment-array to datum (and set :ks yes)
      :z     print the last return value to stdout

ReverseFuck mode

In the 'ReverseFuck' mode all commands are switched to their semantic opposite. Here is an overview:

-      Increments the current cell (under the pointer).
+      Decrements the current cell (under the pointer).
>      Decrements pointer.
<      Increments pointer.
.      Inputs a character to current cell.
,      Outputs a character from current cell.
]      While the current cell value is not zero, do stuff inside ] and [ braces
[      End while.
!      input integer at current cell.
?      output integer from current cell.
@      exit program returning current cel value( the only command not changed).

You can switch to ReverseFuck mode by adding the -r or --reversefuck option to the bfng interpreter.


Hello, World!


This is a slightly more complex variant that often triggers interpreter bugs


bfng - The brainfuck-ng interpreter

  • get the return value:
% echo "+++"|bfng -s
% echo $?
3           #(the putput)
  • give an environment and get the result:
% echo "foobar"|bfng -c -x'+' -o
goobar       #(the output)


% echo "+"|bfng -d'foobar' -p
goobar        #(the output)
  • give an environment and a program from files:
% bfng -b -a
  • simply execute a program
% bfng
  • get input and give output from bf program:
% bfng -x '?+++!'
35                #(user keyboard input)
38                #(program output)
% echo $?
38                #(output)
  • enter interactive shell mode:
% bfng -i

External resources

See also