Central Processing Unit: Central Processing Unit (CPU), the most important part of a computer where actual processing, i.e. the mathematical and logical processing, takes place. It is the brain behind all PC operations. Within a CPU, instructions are written in the form of computer programs, which are carried out by the CPU sequentially. The power of a CPU lies in its ability to carry out these instructions rapidly and flawlessly. The processing capability of a PC is measured in terms of the amount of data processed by its CPU in one operation. The speed of the CPU is measured in MegaHertz (MHz).

A computer has a central clock that keeps all its components in tune with one another. Quicker the clock ticks, faster the computer runs. Over the years, there has been a gradual improvement in the speed of a computer. Intel, leading pioneer in processor development and manufacturing in the world, has recently manufactured a Pentium IV processor, which has remarkable speed upto 3200 MHz (3.2 GigaHertz). Apart from Pentium, there are other processors like Intel Celeron, AMD Athlon, AMD Duron, etc. which have a range of 600 MHz to 1200 MHz (1.2 GHz) and even beyond.