Introduction - If you have any usage issues, please Google them yourself
First, from ASCII, ASCII is a coding specification used to represent English characters. Each ASCII character occupies 1 byte, so the maximum number of characters that ASCII encoding can represent is 255 (00H - FFH). In fact, there are not so many English characters, generally using only the first 128 (00h-7fh, the highest level 0), which includes control characters, Numbers, case letters, and other symbols. The other 128 characters (80h-ffh), which have the highest level of 1, are known as "extended ASCII", typically used to hold English tabs, some phonetic symbols, etc.