All arithmetical and logical procedures 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 also. The rate at which the CPU carries out system instructions is usually referred to as its speed and it is measured in Hertz. The speedier the processing unit is, the more quickly scripts and web applications shall be executed, though the efficiency of the latter depends on other things as well - the read/write speed of the hard disk drive, the amount of physical memory, the network connectivity, and many others. All modern CPUs have several cores, which work together. Thus, the effectiveness and the workload that a CPU can handle increase, since each and every core can process several tasks independently and several cores can handle a single task which cannot be processed by 1 core.