ENQ

from Jargon File (4.4.4, 14 Aug 2003)

ENQ
 /enkw/, /enk/

   [from the ASCII mnemonic ENQuire for 0000101] An on-line convention
   for querying someone's availability. After opening a {talk mode}
   connection to someone apparently in heavy hack mode, one might type
   SYN SYN ENQ? (the SYNs representing notional synchronization bytes),
   and expect a return of {ACK} or {NAK} depending on whether or not the
   person felt interruptible. Compare {ping}, {finger}, and the usage of
   FOO? listed under {talk mode}.

from The Free On-line Dictionary of Computing (8 July 2008)

ENQ

   1. <character> /enkw/ or /enk/ ENQuire.  The {mnemonic} for
   {ASCII} character 5.

   2. <chat> An on-line convention for querying someone's
   availability.  After opening a {chat} connection to someone
   apparently in heavy hack mode, one might type "SYN SYN ENQ?"
   (the SYNs representing notional synchronisation bytes), and
   expect a return of {ACK} or {NAK} depending on whether or not
   the person felt interruptible.

   Compare {ping}, {finger}.

   [{Jargon File}]

   (1998-01-18)