NB: More recent documentation for Dyalog APL is available at https://docs.dyalog.com/20.0/.
This specifies whether source code is discarded for functions and operators when they are created by the editor or by ⎕FIX. See also Discard Source Information.
Y is 0 or 1.
If Y is 0 (the default), source code is retained in the workspace when an object is fixed.
If Y is 1, source code is not retained in the workspace when an object is fixed (source code already retained in the workspace is not discarded).
In all case the result R is the previous setting (0 or 1).
For further information, see Source as Typed.