ENQ

[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.