All arithmetical and logical functions within a computer/server configuration are handled by its Central Processing Unit, or CPU. This hardware part is oftentimes called the "brains" of the computer too. The rate at which the CPU runs system instructions is typically referred to as its speed and it is measured in Hertz. The faster the processing unit is, the speedier scripts and web programs will be executed, although the efficiency of the latter depends on other things too - the read/write speed of the hard drive, the amount of physical memory, the network connection, etc. All modern CPUs have a number of cores, which work together. Subsequently, the overall performance and the workload which a CPU can handle increase, since each and every core can process different tasks separately and numerous cores can handle one task which cannot be processed by one core.