TRUE or FALSE. A light is either ON or OFF. In your
computer, a bit is represented by the voltage on a wire: it
is either HIGH (near 5 volts) or LOW (near 0 volts). The
high value we associate with the symbol '1'. The low value
we associate with the symbol '0'. In order to represent
members of larger collections of objects- letters of the
alphabet, for example, or large numbers, binary digits must
be grouped together.
Four binary digits taken together can represent 16
different objects. (Two to the 4th power.) Eight binary
digits taken together form a unit called a 'BYTE' in
computerese. A byte can stand for any one of two to the 8th
power (or 256) different objects. Your computer deals in
'BYTE' sized Information units. Data flows from one part of
your machine to another along eight wires called the data
bus- in bytes.
In order to specify exactly what information Is being
accessed at a given instant, your computer sends out an
'ADDRESS'. This address is a 16 bit binary quantity that
flows along 16 wires called the address bus. Since there
are 16 address lines, two to the 16th power, or 65536 unique
addresses can be specified by your machine.
Now, instead of using binary numbers directly like your
computer does, it is customary to consider binary digits in
groups of four. Each possible value of this group is denoted
by a symbol: the numbers from 0 to 9 plus the letters A
through F. These are called 'HEXADECIMAL' numbers.
Accordingly, we have the following:
BINARY HEXADECIMAL DECIMAL
0000 0 0
0001 1 1
0010 2 2
0011 3 3
0100 4 4
0101 5 5
0110 6 6
0111 7 7
1000 8 8
1001 9 9
1010 A 10
1011 B 11
1100 C 12
1101 D 13
1110 E 14
1111 F 15
10000 10 16
-3-