You can read the background documentation from Zork III, typed in by Mike Threepoint

You must type commands or sentences like "TAKE ", "OPEN ", "EXAMINE ", "USE WITH ", ecc. ecc. You can move typing "N" (North), "E" (East), "W" (West), "S" (South), "UP", "DOWN", "GO ", ecc. ecc. For a complete example read the Zork Transcript (by Peter Scheyen) or the complete "Beginner's Guide to Interactive Fiction I-F Archive Edition" by Joe W Aultman

To SAVE a game:

1. Type SAVE and then hit <RETURN>; a window will appear (with some "strange" text lines in it);
2. Click on the SELECT button, then press CTRL+C;
3. Open the NOTEPAD and then press CTRL+V; the strange text will be copied in the notepad. You can save the text document to use it later (see restore);
4. Click on the OK button to continue the game.

To RESTORE a (previously saved) game:

1. Type RESTORE and then hit <RETURN>; a window will appear (restore window);
2. Click on the CLEAR button (or simply click on the OK button if the "strange" lines of a previously saved session are still on the window);
3. Open a text document with a previously saved game with NOTEPAD;
4. Select the "strange" text lines in it; then press CTRL+C;
5. Click on the center of the restore window then press CTRL+V (the "strange" text lines will appear in it;
6. Click on the OK button to play the restored game.