Many techniques are employed in numbering lines for text editing. The simplest approach uses a single integer that changes each time a line is added or deleted (1). BASIC, in addition to other systems, uses fixed multi-digit numbers bound to each line. This approach has problems: only a fixed number of lines can be inserted between two consecutive lines of text, otherwise the original text must be renumbered. This negates one advantage of line numbers: the ability to compare different versions of the same document.