# Annotation Glossary

### A

allow-none

  NULL is OK, both for passing and for returning.

array

  Parameter points to an array of items.

### C

closure

  This parameter is a 'user_data', for callbacks; many bindings can pass NULL here.

### N

nullable

  NULL may be passed as the value in, out, in-out; or as a return value.

### O

out

  Parameter for returning results. Default is transfer full.

### S

scope async

  The callback is valid until first called.

### T

transfer full

  The caller owns the data, and is responsible for free it.