We prove that a connected space X is a COTS with endpoints iff there is a one–one Darboux function from X onto a space with endpoints. Using this result, we show that a connected space X is homeomorphic to the closed unit interval if it is class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S016686411500334X&_mathId=si1.gif&_user=111111111&_pii=S016686411500334X&_rdoc=1&_issn=01668641&md5=b31883f4c42faef4368f410641b4ba32" title="Click to view the MathML source">T1class="mathContainer hidden">class="mathCode"> separable and locally connected and there is a one–one Darboux function from X onto a space with endpoints. Also we obtain some other characterizations of COTS with endpoints and some characterizations of the closed unit interval.