The DCT kind of grammar component is used at run time to represent dictionaries (i.e. environments) inside the Pico evaluator. Each DCT-like grammar component has 3 children: a name, its associated value and a link to another dictionary. The latter can e.g. be the lexical scope. Hence, these dictionary components are actually linked lists of (name,value)-pairs. In other words, the Pico environment system can be thought of as a system of association lists. Given a dictionary dd, then its name field is accessed by the expression dd[DCT_NAM_idx]. Its associated value by the expression dd[DCT_VAL_idx], and the 'next-link' to the parent dictionary by the dd[DCT_DCT_idx] expression.