All arithmetical and logical functions in a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware part is usually called the "brains" of the PC as well. The rate at which the CPU runs system instructions is commonly referred to as its speed and it is measured in Hertz. The swifter the processing unit is, the quicker scripts and web programs shall be executed, even though the overall performance of the latter depends upon other things too - the read/write speed of the hard disk, the amount of physical memory, the network connectivity, and so forth. All current CPUs have several cores, which work together. For that reason, the functionality and the workload which a CPU can handle increase, because every core can process different tasks independently and numerous cores can handle one task that can't be processed by a single core.