When a string, an array, or a structure is passed as an argument,
the compiler passes a descriptor for that argument unless the called
routine is declared with OPTIONS(NODESCRIPTOR). There are two methods
for passing such descriptors:
- By descriptor list
- By descriptor locator
The following key features should be noted about each of these
two methods:
- When arguments are passed with a descriptor list
- The number of arguments passed is one greater than the number
of arguments specified if any of the arguments needs a descriptor.
- An argument passed with a descriptor can be received as a pointer
passed by value (BYVALUE).
- The compiler uses this method
when the DEFAULT(DESCLIST) compiler option is in effect.
- When arguments are passed by descriptor locator
- The number of arguments passed always matches the number of
arguments specified.
- An argument passed with a descriptor can be received as a pointer
passed by address (BYADDR).
- The compiler uses this method
when the DEFAULT(DESCLOCATOR) compiler option is in effect.
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