HP 82479A Owner's Manual page 217

HPAF File Standard
For example, to describe the names of the columns, a temperature offset, and the fact that the
temperature units are degrees Kelvin, the descriptor block for a hypothetical file might look like this:
Rec File contents Comments
67 "COLNAMS",3, "TEMP" ,"VISCOSITY","DENSITY" Column names
"OFFSET",1,"2.172" Offset
"DEGREES" ,1,"KELVIN" Units information
{EOF}
H.4 Tag Examples
The HP-71 Data Management Pac uses two tags to describe the fields in a file. The first tag, F I EL.[i=,
indicates that the following data will contain the names of the fields in the file. The second tag,
LEMIZ THE, indicates that the following data will contain the lengths of the fields in the file. Numeric
fields always default to a length of 8 the number of bytes taken in the file by a number.
For example, a file [IHTHOEMhas four fields: two of string type, and two of numeric type. The type
string is HFHF == HH. The contents of the descriptor block are as follows:
"FIELDS" yd, "Fart #"y "Hama" "Ho." "Frice"
The tag FF TELLS is followed by the number of fields, followed by the names.
"LEMGTHS" od, "ey "1S", Mat, tin
The tag L.EHIZTHS is followed by the number of fields followed by the lengths.
The data files generated by the Data Acquisition Pac programs = TR IF, MOMT TOR, and LOIS each write
to the descriptor block. Appendix I, "File Structures", contains a description of the information written to
the descriptor block.
When writing programs that work with the descriptor block, it is essential to be able to find a specific tag
regardless of position within the descriptor block. A program that looks for tags either at the beginning of,
or at a specific place in, the descriptor block may have trouble with files from other application programs.
For instance, a program looking for the IF [E|.[1'= tag should be able to recognize that tag anywhere in
the descriptor block, and not just at the beginning as illustrated above.