All arithmetical and logical functions in a computer/server configuration are handled by its Central Processing Unit, or CPU. This hardware part is oftentimes called the "brains" of the computer also. The rate at which the CPU carries out system instructions is usually referred to as its speed which is measured in Hertz. The speedier the processing unit is, the faster scripts and web programs shall be executed, even though the overall performance of the latter is determined by other things also - the read/write speed of the hard drive, the amount of physical memory, the network connection, and so on. All modern CPUs have several cores, which work together. Therefore, the efficiency and the workload which a CPU can manage increase, since each core can process a number of tasks separately and a number of cores can handle a single task which cannot be processed by a single core.