The operating speed of computers tends to increase significantly, however, this process is not simple. It can be explained, that operating speed depends on how fast the computer facilities are as well as their balance. Modern processors can perform operations within several cycles meanwhile the selection time of big size main memory reaches tens and hundreds of cycles. Although the static memory able to operate at speed equal or close to processor’s operating speed exists, it’s using for main memory is expensive. Problem is solved by installing the small size cache between processor and main memory. Relatively small but very fast memory called cache takes a specific position in modern computer memories system. Cache is a highest level of hierarchical memories system. Cache simulator for exploring of cache behaviour was developed. Cache’s influence on computer efficiency from both theoretical and practical point of view, the latter to be supported with simulation results, is analysed in this master thesis. Comparing the theoretical and test results the influence of different factors to the operation of hierarchical memories system is evaluated. The results of cache simulation show that the operation of hierarchical memory system is impacted by functioning of cache levels, the frequence of accesses to the memory, the hit rate (or miss rate), the cache organisation, line replacement algorithm, cache size, cache line size as well as specific properties of program executed.