ASCII Encoding

01234567
0NULDLE0@P`p
1SOHDC1!1AQaq
2STXDC2"2BRbr
3ETXDC3#3CScs
4EOTDC4$4DTdt
5ENQNAK%5EUeu
6ACKSYN&6FVfv
7BELETB'7GWgw
8BSCAN(8HXhx
9HTEM)9IYiy
ALFSUB*:JZjz
BVTESC+;K[k{
CFFFS,<L\l|
DCRGS-=M]m}
ESORS.>N^n~
FSIUS/?O_oDEL

ASCII stands for the American Standard Code for Information Interchange, and it's the most common way to encode text characters in a byte. The columns are the first hex digit, the rows are the second, so 0x41 is 'A', and 0x39 is '9'. Just to be clear, 0x20 is a space character.

ASCII dates back to the 1960s when teletype machines (a combined keyboard and printer) were in use. The first two columns are sometimes known as control characters. They didn't print anything, but were used to control the printer (e.g. 0x0C, "FF", was "form feed": move to a new page).

If you've ever wondered why your keyboard has a "Ctrl" key, now you know. Holding it down while typing a letter moves you a few columns left into the control characters.

Some examples

<Ctrl>-C gives you ETX (end of text) which has been a popular way to terminate programs. ArdEx continues this tradition.