What is a CPU and what does it do?

The CPU (Central Processing Unit) is a microchip, classed as the brain of the computer. Its job is to interpret the instructions that come from the hardware and software, so that the hardware and software can communicate with each other for example. CPUs have different types (Celeron, Pentium, AMD and so on) and different speeds (600Mhz, 700Mhz, 1.79 (1,790Mhz) and so on). The CPU is one of the main reasons for buying a computer. The faster the CPU can process instructions the faster the computer. However. This is not strictly true. An Intel Pentium 4 is faster than an Intel Pentium 3, in theory. And the "stripped down version" of the Intel Pentium 4 - the Celeron CPU - is supposed to be faster than the Intel Pentium 3. I say supposed and in theory because it depends how you slow the computer down or speed it up.

An Intel Pentium 2 with a 7200rpm hard drive is faster than an Intel Pentium 2 with a 5400rpm hard drive. And Windows 98SE with 256 MegaBytes of memory is faster than Windows 98SE with only 64 MegaBytes of memory. So far this is as expected. However. You can have a Pentium 2 with 256MB of memory and a 7200rpm hard drive that will be faster than a Pentium 3 with only 64MB of memory and a 5400rpm hard drive. This is because even though the Pentium 2 processes instructions slower the instructions are being put into memory a lot quicker. For example. If a Microsoft Word file on the hard drive is being copied into memory, perhaps for printing and/or editing purposes, the copying might be done at 1MB intervals. Whereas when Windows 98SE knows it has more memory it knows it can copy data at 2MB intervals for example. With a faster hard drive as well moving files, installing software, file indexing and so on also becomes faster. So the memory and hard drive make up for the slow CPU.

With time and progress manufacturers have now made it possible for the CPU to be split up into two or four parts (cores), known as Dual Core and Quad Core respectively, which basically means the CPU now has two or four brains to use. These core CPUs spread tasks amonst themselves, making it possible for one brain (core) to print out a document for example while another brain (core) takes care of processing internet tasks for example.