6 Computer Service and Repair
Binary can be compared to a switch. If the
switch is closed, the lamp will be on. This state
is represented by a 1. When the switch is in
the off position, the lamp is dark. This state is
represented by a 0.
This may seem like a system too simple to
represent data in a computer, but let’s compare
it to the Morse code system. The Morse code
system consists of only two tones: a short beep
and a long beep. These sounds are referred to
as a dot and a dash, respectively. See Figure 1-6.
This code resembles a binary system. It has two
conditions. The dots and dashes can be combined
in sequences that represent the alphabet and the
numerals 0 through 9. The Morse code system has
been used to transmit information all over the
world.
Graphics are transmitted in a similar fashion
using a facsimile (fax) machine. The light and
dark areas are represented by the presence or
absence of a transmitted voltage. Again, this is a
form similar to digital electronics. See Figure 1-7,
which depicts two rotating drums. One drum is a
transmitter and the other is a receiver. As you can
see, the two-state condition of digital electronics
can be much more powerful than it first appears.
The ones and zeros of the binary system are
used to represent the high and low voltage signals
that travel throughout the computer system. They
also represent data stored on disks or in memory
chips.
systems. Just as a digital device has only two
states (on and off), the binary system uses only
two numbers: 0 and 1. Look at Figure 1-5 to see
how the binary number system is used to express
different values from zero to fifteen.
Goodheart-Willcox Publisher
Figure 1-5. The binary number system can be used to
represent any integer in the decimal system. This chart
shows binary numbers counting up to 15.
Binary Decimal
0000 0
0001 1
0010 2
0011 3
0100 4
0101 5
0110 6
0111 7
1000 8
1001 9
1010 10
1011 11
1100 12
1101 13
1110 14
1111 15
H E L L O W O R L D
• • • • • • • • • • • • • • • • • • •
Only two states of sound: dots and dashes.
Goodheart-Willcox Publisher
Figure 1-6.
Morse code transfers
letters between two
antennae using
combinations of two
states: dots and
dashes.