Computer hardware systems normally have a number of components. Even a
microcomputer cannot do much without the aid of supporting hardware or peripheral
equipment. The main part of the computer, where all the work or manipulation
is carried out, is referred to as the central processing unit (CPU). The
CPU is often referred to as the brain of a hardware system because it controls
all other hardware and peripheral equipment or devices.
The CPU has its own set of instructions built in its memory chips that cannot
be altered by the user. These instructions are known as read-only memory
(ROM), which the user can access and “read” but cannot change. To load user
programs or instructions into the CPU, another hardware device is required. For
microcomputers, that device is known as a hard disk drive.
Input devices are also needed before the user can interact with the computer.
These input devices include such things as a keyboard, mouse, scanner, bar code
reader, and a stylus writing device. A monitor, also known as a screen, cathode
ray tube (CRT), or video display unit (VDU), is another output device. The monitor
displays information and prompts to the user from the CPU; what is input
from the keyboard by the user; and the result of the work that is being done.
Another output device is a printer, invariably a separate piece of equipment
attached by cable to the computer. When work performed by the user is printed
out, the printed material is often referred to as hard copy to differentiate it from
soft copy, or work that is viewed only on the monitor and might still have further
work needed before a hard copy is output. For example, when a guest is
dining in a restaurant that has a computerized sales system, the server can view
the soft copy of the guest’s check on the monitor during the course of the meal,
and add items to it as the meal progresses. The guest check can be reviewed on
a monitor before printing a hard copy for presentation to the guest.
Obviously, with all these various pieces of hardware in a computer system,
there has to be a high degree of compatibility among them. In addition to compatibility
of hardware, the software used must be compatible with the hardware.