A digital data storage and retrieval system. The system has a first memory for storing a plurality of data quantities, and each data quantity, in the plurality of data quantities, consists of a first number of bits. The system also has a second memory for storing a plurality of compressed data quantities, and each compressed data quantity, in the plurality of compressed data quantities, consists of a second number of bits that is less than the first number of bits. The system also has circuitry for reading data quantities from the first memory and circuitry for writing compressed data quantities, corresponding to respective read data quantities, to non-sequential addresses in the second memory. The system also may include circuitry for reading compressed data quantities from the second memory, and circuitry for writing decompressed data quantities, corresponding to respective read compressed data quantities, to non-sequential addresses in the first memory.