All arithmetical and logical operations within a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware element is typically called the "brains" of the computer too. The pace at which the CPU completes system instructions is usually referred to as its speed and it is measured in Hertz. The speedier the processing unit is, the more quickly scripts and web programs will be executed, even though the overall performance of the latter depends on other things too - the read/write speed of the hard disk, the amount of physical memory, the network connectivity, etc. All new CPUs have several cores, which work together. For that reason, the efficiency and the workload which a CPU can tackle increase, because each core can process a number of tasks separately and several cores can handle one task which cannot be processed by one core.