Monadic ⎕CMD means
⎕CMD'dir'
Volume in drive C is OS
Volume Serial Number is B438-9B76
Directory of C:\Users\Pete\Documents\Dyalog APL-64 17.0 Unicode Files
23/06/2018 15:59 <DIR> .
23/06/2018 15:59 <DIR> ..
23/06/2018 14:53 181,488 default.dlf
13/06/2018 20:13 1,262,296 def_uk.dse
14/06/2018 14:36 108,976 UserCommand20.cache
3 File(s) 1,552,760 bytes
2 Dir(s) 101,371,097,088 bytes free
Dyadic ⎕CMD means
Start Windows Auxiliary Processor
)CLEAR
clear ws
'xutils' ⎕CMD ''
)fns
avx box dbr getenv hex ltom ltov mtol ss vtol