Numerical computer data in many applications contain numerous leading and trailing zeros, and this data feature has been neglected in common source models and related data compression methods. A new approach to source modeling, consisting of the description of this data feature by probabilities p/sub ij/ of data values with i leading and j trailing zeros, is proposed. The entropy of this source model is proved to be less than the entropy of the common ones. Based on this model a few codes of different computational complexity are proposed. Experiments on typical computer files show that the coding algorithms based on the new source and data model considerably outperform existing data compression algorithms.>

A generalized approach to block coding of two-tone images is introduced. Binary N-sequences (blocks) are described. Various conventional block coding techniques are shown to be particular cases of this approach. Numerical examples confirm that, based on the approach, the coding technique outperforms existing techniques. Generalized block coding is proved to be near optimum for encoding sparse binary patterns and advantageous for sources with unknown models.