What is the X in X-mas?
(Unix) On a time-sharing system, a task executing in foreground is one able to accept input from and return output to the user in contrast to one running in the background. Nowadays this term is primarily associated with Unix, but it appears first to have been used in this sense on OS/360. Normally, there is only one foreground task per terminal (or terminal window). Having multiple processes simultaneously reading the keyboard is confusing.