Efficient visualization tools to explore the internal hierarchical task structures of parallel programs have gained a prominent role in the parallel programming community. As such, the IF1 -Viewer is a visual, graphical parallel programming tool developed to aid in the understanding and interpretation of SISAL and IF1 programs. IF1-Viewer consists of two sub-tools: the IF1-Grapher and the IF1-Interpreter. The IF1-Grapher graphically displays the hierarchical directed acyclic task graphs of the IF1 code and the IF1Interpreter visually shows the execution behavior the IF1 code. IF1 ( Intermediate Form) is a machine independent graphical language generated from the SISALS compiler. The IF1-Viewer is a generalpurpose parallel software and with the aid of graphical interfaces, provides a unique way to assist programmers in (1) gaining insight into internal task structures of application programs, (2) alleviating the shortcomings in parallel program implementation, (3) detecting the degree of parallelism in the applications, and (4) understanding the parallel program executing behaviors.