4 Computer Service and Repair
represented with a dimmer switch. Figure 1-3
shows a dimmer switch connected to a lamp. In
this circuit, the intensity of the lamp varies as the
dimmer switch is turned. The light from the lamp
can have different intensities because the dimmer
switch varies the amount of electrical energy that
reaches the lamp.
A computer is constructed of some very
complex digital circuits. These digital circuits
are combined into modules such as circuit board
cards. As a PC technician, you will usually only
be responsible for replacing the module, not
repairing the digital circuits. You do not need an
extensive electronics background to repair a PC.
What Is a Computer?
A computer is an assembly of electronic
modules that interact with computer programs
known as software to create, modify, transmit,
store, and display data. The computer has
rapidly evolved from a simple electronic device
into a highly sophisticated piece of electronic
technology.
Science fiction writers have attributed human
qualities to computers such as Father in Alien:
Resurrection. The computer can appear to be
intelligent, but in reality it only processes and
stores data. Processing data is limited to such
things as sorting items, comparing, and locating
previously stored data. In addition, computers
perform mathematical calculations at amazing
speeds. However, the computer cannot think. The
computer can only be programmed.
This leads to another basic question: What is
data? Data is information. This information comes
in many forms. Data can be text (such as ABC or
123), graphics (pictures), and sounds (music or
voices). Figure 1-4 is an illustration presenting text,
sound, and a picture, followed by digital electrical
voltage symbols.
Data inside the computer is represented
electronically as high and low voltages. The
Digital System
On = 1 Off = 0
Analog System
Off 1/3 power
2/3 power Full power
Goodheart-Willcox Publisher
Figure 1-2.
Typical on/off switch
wired to lamp.
Goodheart-Willcox Publisher
Figure 1-3.
Typical dimmer switch.