Abstract: An I/O control window is created on a user's terminal screen when a parallel program is executing. The I/O control window displays an array of graphical elements (preferably small colored squares), which are partitioned into groups of one or more such elements, each partition representing a task (or thread) of the parallel program. In each partition there is one graphical element which represents the I/O status of the task or thread represented by that partition and is called an I/O status indicator. Each I/O status indicator is capable of assuming any one of several different graphical states (each graphical state preferably being a color for the graphical element), one of which indicates that the corresponding task or thread has provided text output that has not been displayed to the user yet and another of which indicates that the corresponding task (or thread) is requesting text input from the user.