Experiment files contain gel readings plus information about them, and are used during the processing of the sequence. They are used to carry data between programs: they provide input to the programs and programs may in turn add to or modify them. When the experiment file for a reading reaches the assembly program it should be carrying all the data needed for its subsequent processing. The assembly program will copy what it needs into the assembly database. The file format is based on that of EMBL sequence entries and, if required, can be read as such by programs like NIP.