You can use either a semicolon ';' or double forward slash '//' to mark the beginning of a comment line. These markers can be specified either prior to any text on a line, or can follow settings that define and object or property of the building model. These same characters can be included in quoted strings used to name objects or specify property values, in which case they are not interpreted by the file parser as comments. This goes for CBECC-Com (cibd files) as well as CBECC-Res (ribd files).