To prevent accidental changes to documents you want to preserve, save the documents as Read Only. If you then try to write to a read-only document, the program warns you that the document is protected and asks if you want to override the protection or save the document under another name. Protected files are useful for storing document shells that you have developed and that you want to protect from inadvertent changes. Many commands, such as many of those on the Edit menu, are not available when you open a read-only document.