seven-bit ascii improved over prior five- and six-bit codes. of the 2=128 codes, 33 were used for controls, and 95 carefully selected printable characters (94 glyphs and one space), which include the english alphabet (uppercase and lowercase), digits, and 31 punctuation marks and symbols: all of the symbols on a standard us typewriter plus a few selected for programming tasks. some popular peripherals only implemented a 64-printing-character subset: teletype model 33 could not transmit "a" through "z" or five less-common symbols ("`", "{", "|", "}", and "~"). and when they received such characters they instead printed "a" through "z" (forced all caps) and five other mostly-similar symbols ("@", "[", "\", "]", and "^").