Three finger salute
Three finger salute is slang used to describe the IBM PC compatible three key sequence Ctrl+Alt+Del that was developed by David Bradley. This term became popular after IBM PC compatible users continually had to press these keys each time their computer froze or had other issues.
Today, when pressing Ctrl+Alt+Delete, an NMI is sent to the CPU and Microsoft Windows opens a screen that gives access to Lock the computer, Switch users, Sign out, open the Task Manager, and shut down the computer. Earlier versions of Windows only opened the Task Manager, which allows them to see what's running on the computer and have access to End Task open programs.
Is it written as "Alt+Ctrl+Del" or "Ctrl+Alt+Del"?
Although you'll get the same results when pressing these keys in any sequence it more proper to refer to this sequence as "Ctrl+Alt+Del" or "Ctrl+Alt+Delete" in your writing, over the phone, or in person.