Compact format was a data format created by Richard Holmes, basically to save space back in the days when space was an issue on hard disks and for archive facilities. It is a non-standard format, but is output by default in some of Richard Holmes programs (such as FMT). There are no reasons for using this format for storing data today.
The format is quite simple. See the example file below. The first line is header/meta-data for the tree-ring measurements: 93 years, inner ring of 1898, sample ID is ZOC01A. The code (26F3.0) states that 26 measurements exist per line and the measurement is in 3.0 format = 3.0 which would be 0.01 format without the decimal (decimals are superfluous) What the "-2" and "~" signify is unknown to us. One advantage of this format was that the precision was independent for each sample. One could have 3.0 or 4.0 or 2.0 for different cores in the same file.
93=N 1898=I ZOC01A -2(26F3.0)~ 280234187226177190170135184166128151159175216189174178154159163189145186264165 116204222195191171152167155162140144126227228145144165133140127124101113127 97 98103139110 89174149128157 95126127240249193131222241221262212226147265141228 245193243255121158279147 63128 94129100189183
write(outfile,(lastyr-firstyr+1):8,'=N',firstyr:8,'=I ',sitecode); for x := 1 to (48 - length(sitecode)) do write(outfile,' '); writeln(outfile,'-2(',line_length,'F',format_code,'.0)~');
Pascal code used for creating Compact format in the program Convert5