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A Suggested Binary Format Description Method

The basic component of a binary message is a simple field consisting of a consecutive number of bits in the message. Binary messages consist of concatenated fields. A format description for a binary message will consist of a title and four declarative sections.

  1. Symbolic names are declared for all the different kinds of fields found in the binary format being defined.
  2. Symbolic names are declared for commonly used values of particular fields.
  3. The legal ways of concatenating fields are indicated.
  4. The number of bits in each field and any special considerations of bit codings are declared.

The following is a complete example of a binary message description for a trivial kind of pictorial data.

     Title: Illustrative graphic data format for a hierarchally
        structured picture of lines and points.
     Simple Fields:
        OPT   - Option Control Field
        COORD - Numerical Coordinate Value
        ID    - Identnumber for group of picture parts
        COUNT - Number of units in message
     Field Equivalents:
        PHDR   <- '2' OPT
        LHDR   <- '4' OPT
        GRPHDR <- '1' OPT
        GRPEND <- '3' OPT
     Characterizations:
        CPAIR   <- COORD = 2
        POINT   <- PHDR + CPAIR
        LINE    <- LHDR + CPAIR = 2
        PARTS   <- POINT/LINE/PARTS + PARTS
        PIXUNIT <- GRPHDR + ID + PARTS + GRPEND
        PIXMSG  <- '5' OPT + N: COUNT + PIXUNIT = N + '0' OPT
     Simple Field Sizes:
        OPT   3
        COORD 14
        ID    9
        COUNT 6