Trace editing and saving separately

A buffer is the text being edited in memory. Write Out saves it to a
named file. After exiting, reading that file checks stored bytes.
The Nano 7.2 observation below is retained from the earlier course
exercise record; it is not a newly performed session or a guarantee
about every configuration.

Nano 7.2 in a disposable directory. This card is the keystroke record, not a screenshot.
nano note.txt
Type exactly: meeting at ten, then press Enter once.
Ctrl+O: write out; confirm note.txt with Enter; Ctrl+X: exit.
Observed with Nano 7.2: the first line is meeting at ten, and a blank second line is also present.
^O on screen means hold Ctrl while pressing O, not type caret and O.
If a prompt offers to save unexpected changes, read filename and decision;
cancel and preserve work if uncertain. Do not edit host/system files.
Question: buffer changed; exit without saving; no autosave/recovery assumed.
Does disk necessarily hold the new buffer content? yes/no