The SEL command marks a portion of text that will be one end of a select
 range. You create a select range by positioning to one end of the
 desired text (either end will do), executing the SEL command, moving to
 the other end of the desired text, and performing an operation on the SR
 (select range) entity.  On VT100-type terminals the select range is
 displayed in reverse video.

 Format: SEL