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LABEL

The first block of a volume (Block 0) is always a LABEL containing information about the rest of the volume. The format is as following:

    Start Mark            (ASCII 'SOH': 01H)
    File System ID        (VTFS)
    File System Version   (1.0)
    Medium                (ex: T)
    Block Size            (ex: 1024)
    Block Count           (ex: 21)
    Encoding              (ex: A)
    File ID (FID)         (ex: 04)
    File Description      (ex: Employees Master File)
    Read-Only             (Y or N)
    File Creation Date    (ej: 2016-08-11)

These fields are delimited by a Line Feed character (0AH). The last one after the 'File Creation Date' field is interpreted as the end of the LABEL.

Field 'Medium' accept one of the values: 'T' (real Tape), 'V' (Virtual tape). This is important since some VTFS operations (such as overwriting a block in the middle of the tape) are restricted to virtual tapes.

Field 'Block Count' is mandatory for program files but can be ignored for other kind of files, specially those stored in real tapes: having to rewind the tape to the begining for just updating the LABEL can prove impractical in certain cases.

Encoding can be one of the values: 'A' (textual), 'H' (hexadecimal). This is important because VTFS makes the conversion hex-to-bin as it writes to the memory buffer in case of Enconding 'H'.

File ID or FID, is the way programs refer files. When the tape is mount on the tape drive, a 2-digits 7-segments display shows that ID to tell the operator which file is in which drive. This allows the operator to place tapes in arbitrary drives without getting lost.

'File Description' is optional being its purpose to show some additional information in a terminal, if that were the case.