To understand how a
computer process data, you should know how a computer represents data, you
should know how a computer represents data. People communicate through speech
by combining words into sentences. Human speech is analog because it uses
continuous (wave form) signals that vary in strength and quality. Most
computers are digital. They recognize only two discrete states: on and off.
This is because computers are electronic devices powered by electricity, which
also has only two states: on and off.
The two digit, 0 and 1, easily can represent
these two states. The digit 0 represents the electronic state of off (absence
of an electronic charge). The digit 1 represents the electronic state of on
(presence of an electronic charge).
When people count, they use the digits in the
decimal system (0 through 9). the computer, by contrast, uses a binary system
because it recognizes only two states. The binary system is a number system
that has just two unique digits, 0 and 1, called bits. A bit (short for binary
digit) is the smallest unit of data the computer can process. By itself, a bit
is not very informative.
When 8 bits are grouped together as a unit,
they form a byte. A byte provides enough different combinations of 0s and 1s to
represent 256 individual characters. These characters include numbers,
uppercase and lowercase letters of the alphabet, punctuation marks, and others,
such as the letters of the Greek alphabet.
The combinations of 0s and 1s that represent
characters are defined by patterns called a coding scheme. In one coding
scheme, the number 4 is represented as 00110100, the number 6 as 00110110, and
the capital letter E as 01000101. ASCII which stands for American Standard Code
for Information Interchange is the most widely used coding scheme to represent
data.
The ASCII coding scheme is sufficient for
English and Western European languages but is not large enough for Asian and
other languages that use different alphabets. Unicode is a 16-bit coding scheme
that has the capacity of representing more than 65,000 characters and symbols.
The Unicode coding scheme is capable of representing almost all the world's
current written languages, as well as classic and historical languages. To
allow for expansion, Unicode reserves 30,000 codes for future use and 6,000
codes for private use. Unicode is implemented in several operating systems,
including Windows, Mac Os, and Linux. Unicode-enabled programming languages and
software include Java, XML, Microsoft Office, and Oracle.
Coding schemes make it possible for humans to
interact with a digital computer that processes only bit. When you press a key
on a keyboard, a chip in the keyboard converts the key's electronic signal into
a special code that is sent to the system unit. Then, the system unit converts
the code into a binary form the computer can process and store it in memory.
Every character is converted to its corresponding byte. The computer then
processes the data as bytes, which actually is a series of on/off electrical
states. When processing is finished, software converts the byte into a
human-recognizable number, letter of the alphabet, or special character that is
displayed on a screen or is printed. All of these conversions take place so
quickly that you do not realize they are occurring.
Standards, such as those defined by ASCII and
Unicode, also make it possible for components in computers to communicate with
each other successfully. By following these and other standards, manufacturers
can produce a component and be assured that it will operate correctly in a
computer.
