The official Fourth Edition did not appear until 1968, which added several new features on top of the previous additions. This included the ability to define multi-line functions with the codice_10 command, and the powerful codice_43 statement that treated strings as arrays of ASCII-like codes to allow per-character operations without having to loop over the string. This was also the only string manipulation function; to extract a single character or substring, one had to use codice_43 to convert it into an array of numbers, manipulate that array, and then convert it back. This was the reason MAT was 1-based again, as the length of the string was placed in location zero so it was normally ignored.