## Encyclopedia > Befunge programming language

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# Befunge

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Befunge is a stack-based esoteric programming language which differs from conventional languages in that programs are arranged on a two-dimensional grid. 'Arrow' instructions direct the control flow to the left, right, up or down, and loops are constructed by sending the control flow in a circle. This technique is demonstrated in the random number generator program below:

``` vv  <      <
2
^  v<
v1<?>3v4
^   ^
>  >?>  ?>5^
v   v
v9<?>7v6
v  v<
8
.  >  >   ^
^<
```

 `0-9` Push this number on the stack `+` Addition: Pop a and b, then push a+b `-` Subtraction: Pop a and b, then push b-a `*` Multiplication: Pop a and b, then push a*b `/` Integer division: Pop a and b, then push b/a, rounded down. If b is zero, ask the user what result they want. `%` Modulo: Pop a and b, then push the remainder of the integer division of b/a. If b is zero, ask the user what result they want. `!` Logical NOT: Pop a value; if the value is zero, push 1, otherwise zero. ``` Greater than: Pop a and b, then push 1 if b>a, otherwise zero. `>` Move right `<` Move left `^` Move up `v` Move down `?` Move in a random direction `_` Pop a value; move right if value=0, left otherwise `|` Pop a value; move down if value=0, up otherwise `"` Start string mode: push each character's ASCII value all the way up to the next `"` `:` Duplicate value on top of the stack `\` Swap two values on top of the stack `\$` Pop value from the stack `.` Pop value and output as an integer `,` Pop value and output as ASCII character `#` Trampoline: Skip next cell `g` Pop y and x, then pushes ASCII value of the character at that position in the program `p` Pop y, x and v, then change the character at the position x/y in the program to the character with ASCII value v `&` Ask user for a number and push it `~` Ask user for a character and push ASCII value `@` End program

The language was originally created by Chris Pressey in 1993, as an attempt to devise a language as hard to compile as possible - note that the 'p' command allows for self-modifying code. Nevertheless, a number of compilers have subsequently been written. A number of extensions to the original 'Befunge-93' specification also exist, including Funge-98, which extends the concept to an arbitrary number of dimensions and can be multithreaded, with multiple instruction pointers operating simultaneously on the same space.

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