Run Length Encoding

Run length encoding (RLE) is a lossless compression technique. Consecutive repeated symbols are encoded as a pair: the symbol and how many times it appears consecutively. Every group becomes a pair — even a single instance is recorded as (symbol, 1). AQA exam questions accept different notations: (A, 3), A 3, and A3 all represent the same run. This tool uses (symbol, count) notation. RLE reduces size when runs are long; it increases size when symbols frequently change, because each symbol still requires two pieces of data.