CINT was designed to be a scripting language for the ROOT analysis environment. CINT is neither C nor C++ -- it departs subtly from both, but there is no exhaustive documentation of these departures from the respective standards (see http://root.cern.ch/root/html/cint/limitati.html for a few of them).

From their own site, one of the main goals of Cling is to be backward compatible with CINT. This will also mean propagating CINT's numerous idiosyncracies, reducing Cling's scope considerably.