Process simulation programs based on water and steam as a working fluid require the feed of thermodynamic properties during the program runtime. This paper presents the mathematical model necessary to identify the phase and to simulate the thermodynamic properties of water, steam, and wet steam at different temperatures and pressures. The simulated values are compared to the tabulated values and the deviation errors are indicated. A computer program is constructed and visual presentation of the properties on an interactive interface, as well as by plotting on the enthalpy-entropy chart, are presented.