The ALOG library used to write logfiles to be displayed with upshot and nupshot has served us well over the years, but has a number of limitations. The most significant is its fixed record format. An ALOG record contains 6 integers and a 12-character string. The fixed format means that the records are easy to traverse in memory and to parse from files, but also means that it is cumbersome, if not impossible, to add new fields, particularly fields that pertain to only one type of record. The ASCII format in files is excellent for portability and human readability of the files, but awkward for containing binary data. CLOG is more flexible: it contains a variety of predefined record formats, together with a ``raw'' record format that can be used for special cases. It is also relatively easy to extend with new record types without impacting the usefulness of existing logfiles.