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# Brainfuck
Brainfuck is an extremely simple, untyped [esoteric programming language](esoland.md); simple by its specification (consisting only of 8 commands) but intentionally very hard to program in. It works similarly to a pure [Turing machine](turing_machine.md). In a way it is kind of [beautiful](beauty.md) by its [simplicity](minimalism.md). It is very easy to write your own brainfuck [interpreter](interpreter.md).
There exist [self-hosted](self_hosting.md) brainfuck interpreters which is pretty fucked up.
The language is based on a 1964 language P´´ which was published in a mathematical paper; it is very similar to brainfuck except for having no [I/O](io.md).
Brainfuck has seen tremendous success in the [esolang](esolang.md) community as the **lowest common denominator language**: just as mathematicians use [Turing machines](turing_machine.md) in proofs, esolang programmers use brainfuck in similar ways -- many esolangs just compile to brainfuck or use brainfuck in proofs of [Turing completeness](turing_complete.md) etc. This is thanks to brainfuck being an actual, implemented and working language reflecting real computers, not just a highly abstract mathematical model with many different variants. For example if one wants to encode a program as an integer number, we can simply take the binary representation of the program's brainfuck implementation.
In [LRS](lrs.md) programs brainfuck may be seriously used as a super simple [scripting language](script.md).
## Specification
The "vanilla" brainfuck operates as follows:
We have a linear memory of **cells** and a **data pointer** which initially points to the 0th cell. The size and count of the cells is implementation-defined, but usually a cell is 8 bits wide and there is at least 30000 cells.
A program consists of these possible commands:
- `+`: increment the data cell under data pointer
- `-`: decrement the data cell under data pointer
- `>`: move the data pointer to the right
- `<`: move the data pointer to the left
- `[`: jump after corresponding `]` if value under data pointer is zero
- `]`: jump after corresponding `[` if value under data pointer is not zero
- `.`: output value under data pointer as an ASCII character
- `,`: read value and store it to the cell under data pointer
## Implementation
This is a very simple [C](c.md) implementation of brainfuck:
```
#include <stdio.h>
#define CELLS 30000
const char program[] = ",[.-]"; // your program here
int main(void)
{
char tape[CELLS];
unsigned int cell = 0;
const char *i = program;
int bDir, bCount;
while (*i != 0)
{
switch (*i)
{
case '>': cell++; break;
case '<': cell--; break;
case '+': tape[cell]++; break;
case '-': tape[cell]--; break;
case '.': putchar(tape[cell]); fflush(stdout); break;
case ',': scanf("%c",tape + cell); break;
case '[':
case ']':
if ((tape[cell] == 0) == (*i == ']'))
break;
bDir = (*i == '[') ? 1 : -1;
bCount = 0;
while (1)
{
if (*i == '[')
bCount += bDir;
else if (*i == ']')
bCount -= bDir;
if (bCount == 0)
break;
i += bDir;
}
break;
default: break;
}
i++;
}
}
```
## Variants
TODO