All arithmetical and logical functions in a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware part is occasionally called the "brains" of the PC too. The pace at which the CPU runs system instructions is commonly referred to as its speed and it is measured in Hertz. The quicker the processing unit is, the faster scripts and web applications will be executed, though the performance of the latter depends on other things too - the read/write speed of the hard disk drive, the amount of physical memory, the network connectivity, and so on. All modern CPUs have a number of cores, which work together. Because of this, the functionality and the workload a CPU can tackle increase, since every core can process various tasks individually and several cores can handle a single task which cannot be processed by 1 core.