Program design (or software program design) is, in the software systems development, the design and implementation phase. That is, program design means to get a solution to furnish customers' requirements on the software system. When working on the program design, we mainly consider how to manufacture the software system, but not to specify what this software system is. A software system has been designed hopefully to be an integrated whole, embodied in its assembled components, their interactions with each other and the environment. Since software structure and software behavior are the two most prominent views of a software system integrating the software structure and software behavior apparently is the best way to achieve a truly integrated whole of a software system. Because program design 1.0 does not design the integration of software structure and software behavior, very likely it will never be able to actually form an integrated whole of a software system. Structure-behavior coalescence (SBC) provides an elegant way to integrate the software structure and software behavior, and hence achieves a truly integrated whole, of a software system. A truly integrated whole sets a path to achieve the desired program design. SBC facilitates an integrated whole. Therefore, we conclude that program design 2.0 using the SBC approach, which contains three fundamental diagrams: a) framework diagram, b) component operation diagram, and c) interaction flow diagram, is highly adequate in designing a software system.