qalle2 / nes-bf

Brainfuck interpreter (NES)

Qalle's Brainfuck

A Brainfuck interpreter for the NES.

Table of contents:

• List of files
• Features
• Technical info
• How to use
  • Edit mode
  • Run mode
• Character set
• References

List of files

• *.bf: long Brainfuck programs
• assemble.sh: a Linux script that assembles the program (warning: deletes files)
• bf.asm: source code (assembles with ASM6)
• bf.nes.gz: the assembled program (iNES format, gzip compressed)
• chr.bin.gz: CHR ROM data (gzip compressed)
• chr.png: CHR ROM data as an image (can be encoded with nes_chr_encode.py in my NES utilities)
• examples.txt: short Brainfuck programs
• movies.tar.gz: FCEUX movie files that enter a Brainfuck program into the NES program
• snap*.png: screenshots
• txt2fm2.py: a Python script that converts a Brainfuck program into an FCEUX movie file that enters the Brainfuck program into the NES program

Features

• maximum program size: 239 (8×30−1) instructions
• maximum output size: 240 (8×30) bytes
• Brainfuck RAM size: 1,024 bytes
• output speed: 1 character/frame

Technical info

• mapper: NROM
• PRG ROM: 16 KiB
• CHR ROM: 8 KiB
• name table mirroring: vertical
• compatibility: NTSC & PAL

How to use

There are two modes.

Edit mode

• the program starts in this mode
• the cursor (blinking square) is always on the program input area
• note: the Brainfuck program won't run if brackets don't match

Run mode

• there are three submodes:
  • if the cursor is on the output area: the Brainfuck program is running
  • if the cursor is on the virtual keyboard: the user is expected to enter a character
  • if the cursor is next to the B=exit text: the Brainfuck program has finished or the maximum output size has been reached
• press B at any time to return to edit mode

Character set

• output behavior:
  • byte 0x0a moves the cursor to the start of the next line
  • other bytes advance the cursor by one
• output appearance:
  • bytes 0x20 to 0x7e: as in ASCII
  • some bytes from 0x7f on contain special characters
  • other bytes are blank
• input (virtual keyboard):
  • newline symbol (↵ at bottom right) inserts byte 0x0a
  • other symbols insert bytes 0x20 to 0x7e

References

• Wikipedia – Brainfuck
• Esolang – Brainfuck
• NESDev Wiki