A cache is an extremely fast storage with comparatively small storage capacity. It buffers the central processing unit and the working memory. With its help, the access to frequently used programmes and data is significantly accelerated. Both the storage and the reading is executed fully autmatic. To make this possible, the access frequency of the memory areas are monitored, the areas which are used only rarely are overwritten first. The cache is managed either by a special programme or directly by the operation system.