Helper variables are used to store supplementary information for a field. Source file variables are common examples of helper variables. Source file variables store the name of a file that contains an image or a recording of a question response (such as a .tiff file containing a scanned image of a hand-written response, or a sound file that contains a recording of an open-ended response in a Quancept CATI interview).

You specify a helper variable at the end of a Long, Double, Text, Date, Boolean, or Categorical question as follows:

You do not need to specify the helperfields keyword in the following situations as helper variables of the correct data type and usage type are added automatically to the metadata:

This example creates a single source file helper variable for a double field:

The usagetype keyword defines the field as a source file variable. The HelperField usage type is set automatically. For more information, see Special usage types.