Log files are repositories of data produced by iterative programs.
A log file contains a series of records, each identified by its type and its numerical index. Programs may create new log files, or read and append records to an existing log file. Normally, a newly created log file will have various specifications stored in the first few records, with index -1. Other programs will then be able to obtain this data without requiring further user input. Programs of an iterative nature may write indefinite numbers of other records, with the iteration to which each record pertains being identified by its index, from zero on up.