- Part 1 - The File Header (continued):
  - Providing set/get methods for the header fields.
    - We need to make set and get methods for each of the fields in the header. If you look back two pages you will see a table that details the structure of the header.
    - When reading or unpacking data from a buffer, we want to use the `unpack` methods provided by `Convert`.
      - `unpackS(..)`
      - `unpackD(..)`
      These methods take in the buffer to access (`header`) and the byte offset into the buffer (see the table). When unpacking a string, it is necessary to provide the length of the string to read. When unpacking a numeric value, it is necessary to indicate what byte representation is being used (here we are using `EEEI`).
    - When writing or packing data into a buffer, we want to use the `pack` methods provided by `Convert`.
      - `packS(..)`
      - `packD(..)`
      These methods are similar to the `unpack` methods, except that they have an additional parameter for the value that is to be set.
    - For example, here are the set and get methods for XDelta:

            public double getXDelta () {
              return Convert.unpackD(header, 16, EEEI);
            }

            public void setXDelta (double val) {
              Convert.packD(header, 16, val, EEEI);
            }

    - The set and get methods for Version, Format, and XStart are left for you to do.
- continued on next page