Setting null values

The IEWBIND macro generates the necessary null and default values for any omitted parameters. Parameters not coded on the macro are passed as null values, rather than omitting the parameter altogether. Null values for the parameters are as follows:

Parameter	Null value
Varying length character strings	Two bytes of zeros.
Fixed length character strings	Blank
Fullword or halfword integers	Zero, unless zero is a valid value for that parameter (such as OFFSET); then use –1
Doubleword integers (RELOC)	Two words of zeros.
Return and reason codes	Zero parameter address
Data buffers (AREA, XTLST)	Doubleword of zero
Lists (FILES, EXITS, OPTIONS)	Fullword of zero
Addresses	Zero
Tokens	Fullword or doubleword of zero depending upon the token length. DIALOG, WORKMOD, and EPTOKEN are 8 bytes; use a doubleword
WKSPACE (workspace) parameter	Doubleword of zero