# Fm

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For each m >= 2, **Fm** is a computational model based on editing a finite
unbounded string on an alphabet of m letters. It is derived from Brainfuck
in the spirit of the Wang program formulation of Turing machines, by using
only the five instructions '+' '<' '>' '[' ']' and by applying a cyclic
ordering to the alphabet, with '+' changing a letter to the next letter
in cyclic order.

## Computational class

F2 has been proved Turing-complete without reference to the Turing completeness of other Brainfuck languages, by directly simulating a universal tag system in F2. All Fm languages are therefore Turing-complete, because they can easily simulate F2.

## External resources

*Original*pre-Geocities Fm page*(from the Wayback Machine; retrieved on 28 January 2007)*that*is*archived. The more frequently referenced Geocities page of r_e_s_01 appears lost.- F resources
*(from the Wayback Machine; retrieved on 12 March 2006)*, with code and examples, including:- Interpreter in Python
*(from the Wayback Machine; retrieved on 17 May 2006)* - F2 tag system TC proof
*(from the Wayback Machine; retrieved on 17 May 2006)*

- Interpreter in Python