When the application starts, it should display a message asking the user to enter either option d or v. The application should execute the following actions for the two options: d: The application should display the file extension of the stock details. v: The application should open the stock details file in the read-only mode and display its contents.
Write the code snippet that Hayley should use to implement the desired functionality in the application.
In case the user presses any other key, the application should open the stock details file in the read/write mode, display a message to enter new stock details, and save the details that the user has entered. Write the code snippet that Hayley should use to accomplish the preceding task.