ASCII art is a graphic design technique that uses computers for presentation and consists of pictures pieced together from the 95 printable (from a total of 128) characters defined by the ASCII Standard from 1963 and ASCII compliant character sets with proprietary extended characters (beyond the 128 characters of standard 7-bit ASCII). The term is also loosely used to refer to text-based visual art in general. ASCII art can be created with any text editor, and is often used with free-form languages. Most examples of ASCII art require a fixed-width font (non-proportional fonts, as on a traditional typewriter) such as Courier for presentation. Among the oldest known examples of ASCII art are the creations by computer-art pioneer Kenneth Knowlton from around 1966, who was working for Bell Labs at the time. "Studies in Perception I" by Knowlton and Leon Harmon from 1966 shows some examples of their early ASCII art. ASCII art was invented, in large part, because early printers often lacked graphics ability and thus, characters were used in place of graphic marks. Also, to mark divisions between different print jobs from different users, bulk printers often used ASCII art to print large banner pages, making the division easier to spot so that the results could be more easily separated by a computer operator or clerk. ASCII art was also used in early e-mail when images could not be embedded. History Typewriter art Since 1867, typewriters have been used for creating visual art. TTY and RTTY TTY stands for "TeleTYpe" or "TeleTYpewriter", and is also known as Teleprinter or Teletype. RTTY stands for Radioteletype; character sets such as Baudot code, which predated ASCII, were used. According to a chapter in the "RTTY Handbook", text images have been sent via teletypewriter as early as 1923. However, none of the "old" RTTY art has been discovered yet. What is known is that text images appeared frequently on radioteletype in the 1960s and the 1970s. Line-printer art In the 1960s, Andries van Dam published a representation of an electronic circuit produced on an IBM 1403 line printer. At the same time, Kenneth Knowlton was producing realistic images, also on line printers, by overprinting several characters on top of one another. Note that it was not ASCII art in a sense that the 1403 was driven by an EBCDIC-coded platform and the character sets and trains available on the 1403 were derived from