Stack Comments are a conventional notation in Forth that specify the arguments that a word expects, and the results it will return. It is usual for a Forth word to consume its arguments. A stack comment looks like this;
( a b c--d e)
The arguments come before the "--", and the results after. In each instance the rightmost item (respectively "c" and "e" in the example), is on the top of the stack. It is usual for stack comments to carry data type information, where it is required (ie n1 would be a signed integer, addr2 would be an address).