## Backward compatibility

NOEMA, previously Plateau de Bure Interferometer (PdBI), has seen continous improvements since its start, with more than five generations of receivers and correlators along with the development of atmospheric phase correction techniques. Given the nature of the CLIC data file, this was associated with many, sometimes small, changes of the data format. CLIC is designed so that its latest version can read and process any version of the data format and map it in memory to the latest data format. Data of any date can hence be processed with the latest CLIC version. Note that writing the data is always done with the latest data format (except if one updates an observation, i.e. modify an existing .hpb file). In practice, the data format used the section length (stored in the file) to see whether there were extensions to a section. With the introduction of CLASSIC , a version number is stored with the observation.