Meaning – The term read-only, refers to data that can be read but cannot be modified.
Most operating systems, such as Windows and OS X allow you to mark individual files as read-only. In Windows, you can right-click a file and select Properties to view more information about the file. You can click the Read-only checkbox (located in the General tab) to make a file read-only. I
n OS X, you can right-click a file and select Get Info to view more information about the file. You can then select the Locked or Stationery options in the file’s Get Info window to disable write access to the file. A “locked” file on a Mac is the same thing as a read-only file in Windows.
Example of usage – “A read-only file or storage device contains data that cannot be modified or deleted. While data can be accessed or “read” from a read-only file or device, new data cannot be added or “written,” to the device.”