Abstract: An output window is created on the user's terminal screen when a parallel program is executing. This window displays an array of graphical elements (each preferably a small square area), which are partitioned into groups of one or more graphical elements per group, each partition representing a task or thread of the parallel program. These graphical elements are capable of assuming any one of several (or many) different graphical states (each of these states preferably being a different color for the graphical clement). A task running on a parallel processor system can set its associated graphical elements to different states (e.g., colors) during execution of the task generally through a special instruction in the task that specifics which graphical clement (of the graphical elements assigned to that task) should be set and to what state. When such an instruction is executed by a processor running that task, a message is sent to the module that controls the graphical element display at the user's terminal.