intitle:index.of vs intitle:"index of" for directory listings

The correct operator to use for directory listings is **intitle:"index of"**.

1. **Understanding Directory Listings**: Directory listings occur when a web server displays a page listing the files and subdirectories within a directory, often with a title that includes "Index of" followed by the directory path.
2. **Intitle Operator**: The `intitle:` operator is used to search for pages that have specific words in the title. In this case, to search for directory listings, you would use `intitle:"index of"` to match the title format exactly.
3. **Quotation Marks**: It is important to use quotation marks around the phrase "index of" when using the intitle operator, as this tells Google Search to search for the exact phrase in the title and not as separate words. The use of a dot (.) does not function similarly to a space in this context, so it is not a valid alternative.
4. **Teacher's Guidance**: Your teacher is correct in advising you to use `intitle:"index of"`. This is the proper way to search for directory listings based on the title format commonly used by web servers.

In conclusion, for searching directory listings based on the title "Index of" followed by the directory path, the correct and proper method is to use the intitle operator with quotation marks, as in `intitle:"index of"`.