The original character set was composed of 128 characters in 7-bit code, the frost 32 being control characters. When it expanded to 256 characters (8-bit code) so that language specific characters such as the circumflex were provided, as well as box ddawing characters. I am not aware of any going beyond this number. Pretty well anything you can think of is provided for such as a no-break space and 3 shades of a colour.
There is a simple reason as to why there are only 256 total ASCII codes. ASCII is a program language that is geared for 8 bit graphics. ASCII was a computer language that was real popular in the early days of computer gaming with the making of the graphics for those games. That means that there are 256 characters in the language thus comes the reason that there are 256 total codes in the ASCII computer language.
ASCII actually stands for American Standard Code For Information Exchange and is one of the oldest telecommunications codes and programming languages around today. It actually started out as a code to be used with telegraph machines. It eventually became widely used in word processors and eventually in home computers.It was one of the first languages that became widely known by the general computing public to the point where they could learn on their own to operate the ASCII language to make their own programs. ASCII code and language is still used to this day in various data applications and other integral coumputing solutions.