A button allowing you to select one option from among many. Named for the push buttons on your car radio. The temporary memory in which a computer stores information while it's running. Ordinary RAM is volatile - it loses its content when the power goes off.
RAM is also extremely fast.
You can change the amount of RAM reserved for each program in the Get Info window, also available from the desktop. A special area of RAM which can be used to store information which your Mac's processor needs frequently. A file or a disk is read-only when you can look at and print its contents, but cannot save changes to it. Often you may think you can, because the file lets you select and edit text, but you won't be allowed to Save. Locking a disk or file will make it read-only.