An automatic synthesis system for real-time software is described. It is argued that the presence of strict operation requirements, such as task-level timing constraints and compiler and target platform constraints, guides synthesis. An automatic software synthesis system, RT-SYN, integrates platform characteristics to synthesize real-time software which meets hard deadline design requirements. The RT-SYN system has four key features. First, a visual graphical user interface captures application algorithms without implementation specifications. Second, RT-SYN analyzes the task-level data and control flows to produce worst-case timing and space predictions. Third, RT-SYN uses these predictions to choose abstract representations of data structure and algorithm implementations to meet required timing and space constraints. Fourth, RT-SYN synthesizes C code from the selected implementations. Experimental results are given to illustrate these four features.>