nop operation?

[webmasterpdx]

I was curious how CAS handles parsing when spaces are put in composite operators.
I typed:
typed LHS of stack RHS of stack
a:=3 3
a+=1 increment(a) 4
a+ =1 a+nop(1) 5

What is the nop operation? I tried the help command and it isn't documented.

Thanks
-Donald