Character codes from 32 to 127: Punctuation marks, lowercase and uppercase letters, numbers and other commonly used symbols. Starting with the Spacebar and ending with the delete Key. These are printable characters and you can find most of them on your keyboard.
Character codes from 128 to 255: the extended eight-bit ASCII characters include the standard seven-bit ASCII characters above, plus additional symbols and letters with a grave, acute, circumflex, tilde, umlaut and other marks.
Character codes from 0 to 31: The ASCII control characters are the first 32 codes. These are used to control printers and other peripherials. They are not visible and they render blank if displayed on the screen:
null character, start of heading, start of text, end of text, end of transmission, enquiry, acknowledge, bell, backspace, character tabulation, line feed (lf), line tabulation, form feed (ff), carriage return (cr), shift out, shift in, data link escape, device control one, device control two, device control three, device control four, negative acknowledge, synchronous idle, end of transmission block, cancel, end of medium, substitute, escape, information separator four, information separator three, information separator two, information separator one
The ASCII table lists the first 256 character codes. ASCII is an abbreviation of American Standard Code for Information Interchange, pronounced as ASS-kee. It's a character encoding standard. ASCII codes represent text in computers, telecommunications equipment, and other devices. Most modern character-encoding schemes are based on ASCII, although they support many additional characters.