Call site
In programming, a call site of a function or subroutine is the location (line of code) where the function is called (or may be called, through dynamic dispatch). A call site is where zero or more arguments are passed to the function, and zero or more return values are received.
In some occasions, return is an efficient method of indicating success or failure. return may be accomplished by returning at +0 or +4,+8, +12, etc. requiring a small branch table at the return point - to go directly to process the case (as in HLL Switch statement).
Conventionally however, a return code is set in R15 (0=OK, 4= failure, or similar ..) but requiring a separate instruction to test R15 or use directly as a branch index.
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