8.4 Determining Input and Output Formats

You can optionally include the read/write type ("input" or "output") in format descriptors, e.g., ASCII_input_data. You may not want to specify the read/write type in some circumstances. For example, you may need to translate from native ASCII to binary, then back to ASCII. ASCII is the input format in the first translation and the output format in the second translation, vice versa for binary. You would need to edit the format description file before executing the second translation if you included read/write type in the format descriptors.

NOTE: If you use the -ft option, you do not need to edit the format

description file. See Section 8.6.2 later in this chapter.

If you do not specify read/write type, FreeForm ND can nevertheless determine which format in a format description file is input and which is output as long as you have adhered to FreeForm ND filenaming conventions.

• If the input format is not specified, and
  • the input data filename extension is .bin, assume binary input.
  • the input data filename extension is .dab, assume dBASE input.
  • the input data filename extension is .dat, assume ASCII input.
  • the input data filename extension is anything else, assume binary input.
• If the output format is not specified, and
  • the input format is binary, the output is ASCII or dBASE, whichever is found first.
  • the input format is dBASE, the output is ASCII or binary, whichever is found first.
  • the input format is ASCII, the output is binary or dBASE, whichever is found first.

NOTE: The appropriate format descriptions must be in the format

description file(s) used by FreeForm ND for a translation. If, for example, FreeForm ND determines the input format is binary and the output format is ASCII, there must be a format description for each type.

The checkvar program needs only an input format.