.HM Files are text files containing lists of ContextStrings with their corresponding HelpIDs, in Hexadecimal format. These files are usually produced by programs like ForeHelp. A typical HM file looks like this:
Each line is prefixed with "#define", followed by the ContextString, then the HelpID in Hex.
When Fast-Help imports each line, it firstly checks to see if the ContextString exists in this project. If it finds it, it then compares the existing HelpID. If it is different to the one in the Import file, then it replaces it with the import HelpID.
If the ContextString is not found, then the HelpID is searched for. If that is found, then the ContextString is compared and if it is different then it is replaced with the imported ContextString.
When complete, a text file is displayed showing the results of what happened, i.e. what was changed and what was ignored.