Files must have a header associated with them that describes the data and formatting within the file (see below). This header may either be at the top of the file itself (attached) or in a separate file (detached). Detached header files are identified by the extension ``.qfh''. The first such file found in the directory is used. The header may provide formatting information for a series of files which all have the same record structure.
If the header is attached, the data records must be
immediately preceded by a line:
Start_data = xxx
where xxx is an integer specifying the number of records to follow.
If the number of data records is unknown, this value may be set to zero.
An exclamation mark is used as a comment marker, and all input to the right of this marker up to the newline character is ignored on input.
Blank lines (where the first character is the newline character, or contain only space characters or tabs) are ignored.
If a file does not have an attached header, the directory is searched for a
detached header (*.qfh). The first header file located is used. This means that
the appropriate header must be available and unique within a data directory.
Thus no more than one header and its associated data
files should reside in a directory and the header file can take any name with the
extension ".qfh". For files consistent with CSDS file naming, the header
SC_RR_INS_EXTN_Vnn.qfh
could be associated with files
SC_RR_INS_YYYMMDD_EXTN_Vnn.qft (.qfd)
where SC is the mission identifier, RR the resolution,
INS the instrument,
EXTN the local processing specific extension and Vnn the version number for this
processing.