oa -- Option Absolute default range syntax 1,$ oa "oa" toggles the Absolute line numbers flag, which determines whether the numbers in the left margin shall be absolute line numbers, or the (usually capital) letters that refer to lines by the position at which they are being displayed on the screen. In any case, the current line is always shown as "." (with the "->" arrow to make it easy to find), the first line in the buffer is labeled "1", and the last, "$" (when not "."). Lines can be referred to by letter ONLY when the letters appear in the left margin. For general information about the option command, type "ho". See also "hln" for how lines can be referred to in commands.