ASCII vs Unicode
How binary is used to represent characters
In ASCII every character is represented by a binary number.
The 8 bit ASCII code below represents the upper case letter A:
If you wanted to represent the word JOHN in ASCII, it would look like this:
01001010 01001111 01001000 01001110
Notice that the highest bit is zero in the examples shown above. This means that standard ASCII only uses the first 128 numbers available out of a possible 256.