[parameter_attribute, ...] type_specifier parameter_declarator;

The parameter declaration defines operation parameters.

parameter_attribute

Specify a parameter attribute. The following attributes can be specified:

• in
  Specifies an input parameter.
  
• out
  Specifies an output parameter.
  
• ptr
  Specifies a complete parameter.
  
• ref
  Specifies a reference parameter.
  
• string
  Specifies a character string.
  

type_specifier

Specify a parameter data type. The following types can be specified:

• Basic type and structure

parameter_declarator

Specify a parameter declarator. The following values can be specified:

• Simple declarator
• Pointer
• Fixed-length one-dimensional array

1. Either in or out must be specified.
2. The parameter of the out attribute must be an array or an explicitly declared pointer. An explicitly declared pointer is a pointer declared with *.

• union and enum cannot be used as the configuration type.
• A pointer to a function or array cannot be specified as a declarator.
• Adjustable and variable-length arrays cannot be used.
• Multi-dimensional arrays cannot be used.
• The following type attributes cannot be used:
  Array attribute, context_handle, vl_struct, vl_array, vl_string, and vl_enum
  
• If the string attribute is specified, it is simply ignored without causing an error.