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. The user can open a text window on the user's terminal screen which is dedicated for I/O with a particular task (or thread) by placing a mouse on a graphical element in the I/O control array partition representing that particular task (or thread) and pressing a specified mouse button. Many separate I/O windows like this may be opened at the same time and any I/O window can be closed as well through use of the mouse.