Journal of Digital Information Management Guanci Yang, Jing Yang 15 5 2017 http://dline.info/fpaper/jdim/v15i5/jdimv15i5_1.pdf This paper mainly aimed to investigate the compiling problem of ladder diagrams (LDs) that coordinate with a soft-PLC system running on PCs or embedded intelligent terminals to accomplish corresponding control functions. The data structure to store the LDs was designed according to the series and the parallel logic relationship among LD instructions. Then the procedure to compile the LDs into a binary logic tree was detailed by adopting the principles of the binary tree, in which the child leaves represent the instructions, and the father nodes reflect their series or parallel relationship. Post-order traverse of the binary logic was used to parse the control logic, and logical expression was employed to proof the correctness of the transformation. The proposed method was compared with one algorithm. Statistical results on time overhead and interrupt response time showed that the proposed method performs better in most cases, indicating its superior capability to run the control logic. Finally, an example of the application in the central air conditioning control area is discussed as the case study to illustrate the proposed methodology.