Some functions on Mac OS X remain the same regardless of the software you use, including the ability to highlight or select all content in different applications. The “Select All” function makes life easier whether you are copying text, organizing files and folders, deleting content or even making a music playlist. You can access the “Select All” function through the top menu bar that is always present on your Mac, or by using a keyboard shortcut command.
Open the item, document, file or window in which you want to select everything.
Select any item in the window. For example, if selecting music, click any song; if selecting files, click any one file; or if selecting text, click anywhere in the text document.
Select “Edit” from the top menu bar, then select “Select All.” Alternatively, hold the “Command” key -- sometimes called the “Apple” key -- and the letter “A” at the same time to select all.