CHANGE INDENTATION
          adds or deletes leading blanks or tabs in the select
          range.

      ENTER TAB
          inserts indentation at the beginning of a line or a
          tab at the cursor position.

      SET INDENTATION
          changes the inentation level for the buffer.

      SET TAB_INCREMENT
          specifies the number of columns between tab stops.

      TAB
          inserts blanks and tabs to move cursor to current indentation
          level or next tab stop.

      UNTAB
          removes blanks and tabs to the left of the cursor moving the
          cursor to the previous tab stop.