Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.In computer science, efficiency is used to describe properties of an algorithm relating to how much of various types of resources it consumes. The two most frequently encountered are speed or running time - the time it takes for an algorithm to complete, and 'space' - the memory or 'non-volatile storage' used by the algorithm during its operation but also might apply to transmission size - such as required bandwidth during normal operation or size of external memory- such as temporary disk space used to accomplish its task and perhaps even the size of required 'longterm' disk space required after its operation to record its output or maintain its required function during its required useful lifetime (examples: a data table , archive or a computer log) and also the performance per watt and the total energy, consumed by the chosen hardware implementation (with its System requirements, necessary auxiliary support systems including interfaces, cabling, switching, cooling and security), during its required useful lifetime. See Total cost of ownership for other potential costs that might be associated with any particular implementation.