Text is represented in computers using character encoding schemes like ASCII and Unicode that assign a unique binary number to each character. When a key is pressed on a keyboard, the character is converted to its binary number using the encoding scheme so it can be processed and displayed by the computer. ASCII encodes the most common English characters using 7-bit binary numbers, but is limited to 128 characters total. Unicode was created to support encoding characters for more languages using 16-bit or 32-bit binary representations.

1. Computer Science
CIE-Syllabus 2210
Lesson 17
Representing Text
Tutor: Suraj Motee

2. Learning outcomes
By the end of this lesson, you should be able to :
a) Explain how text is stored on the computer.

3. Representing text When any key on a
keyboard is pressed,
it needs to be
converted into a
binary number so
that it can be
processed by the
computer and the
typed character can
appear on the
screen.

4. Representing text • A code where each
number represents a
character can be used
to convert text into
binary.
• One code we can use
for this is called ASCII.
• The ASCII code takes
each character on the
keyboard and assigns
it a binary number.

5. ASCII CODE • Text characters start
at denary number 0 in the
ASCII code, but this covers
special characters including
punctuation, the return key
and control characters as well
as the number keys, capital
letters and lower case letters.

6. ASCII CODE • ASCII code can only store 128
characters, which is enough for
most words in English but not
enough for other languages.
• Therefore another code,
called Unicode, was created.