The 128 bytes you are talking about could be anything depending on what platform your are on, which compiler you are using and exactly how your variable length file was defined (ie: sequential, line sequential, indexed etc.)
I do not believe anyone can answer your questions without knowing more detail about your file. Additionally, Vendors of PC compilers are not known for giving out what all the extra control characters in various file types really stand for. I think they expect you to use their utilities and programs to read these files.
As a general rule, variable length line sequential files do not have any of these control bytes included in the file. Just the standard x'0D0A' to indicate the end of line.
In the IBM mainframe, what goes in front of a variable length records is a block length in binary followed by a binary record length in front of each record.
etom
As you can see, it is not an easy answer without many more details.