Data in an Xtal archive file is separated into blocks referred to as logical records. The names of these records lrhist: , lrrefl: , lratom: , etc. indicate the nature of the data stored therein. The length of a logical record varies depending to the type of data it holds, the nature of crystal structure being processed, and the current state of the crystallographic analysis. A logical record is subdivided into a sequence of packets, each representing a logical subset of the data. Data for a reflection measurement, or an atom site, are typical record packets. There are two types of records: fixed format (F) and directory (D) in which the first packet contains the ID numbers of data values that follow.

The system names for logical records are lr < name > :. However, in the text archive files ( .aaaor .arc) the logical records are identified by the data names starting with < name > _.

Only the contents of archive files are described here. Information about the contents of auxiliary binary data files must be obtained from the source file of the generating program.

Each logical record is listed as:

A header line containing:

A second line with the packet size information.

For fixed format records, the column headed SEQ gives the packet indices for items listed. For directory records, the column headed IDN gives the identification (ID) numbers of the items that may appear in the logical record. Remember that these are the numbers which are stored in the first packet of a directory record.