All arithmetical and logical operations within a computer/server configuration are addressed by its Central Processing Unit, or CPU. This hardware part is usually called the "brains" of the PC too. The rate at which the CPU executes system instructions is also referred to as its speed and it is measured in Hertz. The speedier the processing unit is, the faster scripts and web applications will be executed, though the performance of the latter is dependent upon other things also - the read/write speed of the hard disk, the amount of physical memory, the network connectivity, and so forth. All modern CPUs have several cores, that work together. As a result, the effectiveness and the workload a CPU can manage increase, since every core can process several tasks individually and several cores can handle a single task that can't be processed by one core.