Wouldn't it be something to look at GIF compression? some other thing to look at: RLE (already Z80, not so good compression) Huffman (already Z80, better compression) Lite86 (already Z80, Ti-86, already has a compressor/decompressor) bloat (something like Lite86, also Ti-86 *only*) PCX (is this a compressed format?) ZIP LZW PNG (Portable Network Graphics) seems to be also getting good compression results. Henk Poley