Brainfuck (bf) is an esoteric, Turing-complete programming language famous for its minimalistic, eight-character syntax.
Brainfuck is an esoteric and turing complete programming language famous for its minimalistic eight character syntax.
Brainfuck uses a simple machine model consisting of the program and instruction pointer, and an array of at least 30,000 byte cells initialized to zero. There is a movable data pointer (initialized to point to the leftmost byte of the array), and two streams of bytes for input and output (most often connected to a keyboard and a monitor respectively, and using the ASCII character encoding).
Language syntax
There are 8 language commands, each represented with a single character:
>- increment the data pointer (to point to the next cell to the right)<- decrement the data pointer (to point to the next cell to the left)+- increment (increase by one) the byte at the data pointer-- decrement (decrease by one) the byte at the data pointer.- output a character, the ASCII value of which being the byte at the data pointer,- accept one byte of input, storing its value in the byte at the data pointer[- if the byte at the data pointer is zero, then instead of moving the instruction pointer forward to the next command, jump it forward to the command after the matching ] command]- if the byte at the data pointer is nonzero, then instead of moving the instruction pointer forward to the next command, jump it back to the command after the matching[command.
All other characters in the source code are ignored, and there is therefore no special syntax for comments. Despite its minimalistic approach the language is Turing-complete, meaning that any algorithm can be implemented in Brainfuck.
Language semantics
Brainfuck language pseudocode
> becomes ++p;
< becomes --p;
+ becomes ++*p;
- becomes --*p;
. becomes putchar(*p);
, becomes *p = getchar();
[ becomes while (*p) {
] becomes }
Hello world Program
The following represents a program that outputs Hello, world! followed by newline \n:
++++++++++[>+++++++>++++++++++>+++>+<<<<-]
>++.>+.+++++++..+++.>++.<<+++++++++++++++.
>.+++.------.--------.>+.>.
The following represents same code with explanation of how it proceeds:
[ This program prints "Hello World!" and a newline to the screen, its
length is 106 active command characters. [It is not the shortest.]
This loop is a "comment loop", a simple way of adding a comment
to a BF program such that you don't have to worry about any command
characters. Any ".", ",", "+", "-", "<" and ">" characters are simply
ignored, the "[" and "]" characters just have to be balanced. This
loop and the commands it contains are ignored because the current cell
defaults to a value of 0; the 0 value causes this loop to be skipped.
]
+++++ +++ Set Cell #0 to 8
[
>++++ Add 4 to Cell #1; this will always set Cell #1 to 4
[ as the cell will be cleared by the loop
>++ Add 2 to Cell #2
>+++ Add 3 to Cell #3
>+++ Add 3 to Cell #4
>+ Add 1 to Cell #5
<<<<- Decrement the loop counter in Cell #1
] Loop till Cell #1 is zero; number of iterations is 4
>+ Add 1 to Cell #2
>+ Add 1 to Cell #3
>- Subtract 1 from Cell #4
>>+ Add 1 to Cell #6
[<] Move back to the first zero cell you find; this will
be Cell #1 which was cleared by the previous loop
<- Decrement the loop Counter in Cell #0
] Loop till Cell #0 is zero; number of iterations is 8
The result of this is:
Cell No : 0 1 2 3 4 5 6
Contents: 0 0 72 104 88 32 8
Pointer : ^
>>. Cell #2 has value 72 which is 'H'
>---. Subtract 3 from Cell #3 to get 101 which is 'e'
+++++++..+++. Likewise for 'llo' from Cell #3
>>. Cell #5 is 32 for the space
<-. Subtract 1 from Cell #4 for 87 to give a 'W'
<. Cell #3 was set to 'o' from the end of 'Hello'
+++.------.--------. Cell #3 for 'rl' and 'd'
>>+. Add 1 to Cell #5 gives us an exclamation point
>++. And finally a newline from Cell #6
This article is based on the one found in Wikipedia.
