Introduction - Java Concepts - page 4

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Figure 1

Central Processing Unit

At the heart of the computer lies the central processing unit (CPU) (see Figure 1 ). It
consists of a single chip (integrated circuit) or a small number of chips. A computer
chip is a component with a plastic or metal housing, metal connectors, and inside
wiring made principally from silicon. For a CPU chip, the inside wiring is enormously
complicated. For example, the Pentium 4 chip (a popular CPU for personal computers
at the time of this writing) contains over 50 million structural elements called
transistorsȌthe elements that enable electrical signals to control other electrical
signals, making automatic computing possible. The CPU locates and executes the
program instructions; it carries out arithmetic operations such as addition, subtraction,
multiplication, and division; and it fetches data from storage and input/output devices
and sends data back.

At the heart of the computer lies the central processing unit (CPU).

The computer keeps data and programs in storage. There are two kinds of storage.
Primary storage, also called random-access memory (RAM) or simply memory, is fast
but expensive; it is made from memory chips (see Figure 2 ). Primary storage has two
disadvantages. It is comparatively expensive, and it loses all its data when the power is
turned off. Secondary storage, usually a hard disk (see Figure 3 ), provides less