2 Computers and computer systems
Figure 2 shows an advertisement for a laptop. The main features of the computer are listed in this advert. One item on the list is ‘Processor: AMD E450 1.65 GHz’. So this computer uses an AMD E450 processor, running at a speed of 1.65 GHz. A processor is an essential component of a computer; it carries out, or executes, the instructions that make up the computer program. PCs use one main processor and several other ‘supporting’ processors, and adverts for PCs often specify what main processor they use. The speed of the processor (1.65 GHz in this instance) is a measure of how fast the processor can carry out each instruction. (Don't worry if you don't understand the term ‘GHz’ and other specialised terms used in the advert such as ‘Ram: 6gb DDR3’. These will be explained as the course progresses.)
You may remember that the quote from Danny Hillis in Section 1 mentioned a microprocessor. The term microprocessor was introduced when processors were first made on a single silicon chip, with the prefix ‘micro’ emphasising their small size. Today, however, the fact that a processor can be made on a single silicon chip is taken for granted and the term ‘microprocessor’ is not so often used. This course will generally use the term ‘processor’.
All computers, not just PCs, contain processors, so all those ‘invisible’ computers I listed earlier will contain a processor. However, the processor they use will not necessarily be the same as that used in a PC. For example, the processor used within a central-heating controller would not be the same as the main processor used in the personal computer you may be using to study this course. The processor in the personal computer has to carry out a much more complex set of tasks and execute its instructions much more quickly than the processor in the central heating controller. As a result the PC's processor is likely to be physically larger and more costly. However you will see later in the course that the complexity and speed of operation of processors has increased dramatically. As a result, the ‘simple’ processor in an electronic central heating controller may be very similar to a processor which was considered ‘state of the art’ a decade or two previously.