In this research article, semiloof shell element was used to study the behaviour of plate and shells under mechanical and thermal load for stress, free vibration, initially stressed vibration, mechanical buckling, and non-linear vibration. In the above cases, the material properties: Isotropic, Composite and Functionally Graded Material (FGM) were considered. Wherein, the material property for the FGM shells was assumed to vary through the thickness of the shell by varying the volume fraction of the constituent, whereas, for composites, classical laminated theory was used. Utilizing the semiloof shell element, and the above material properties, the package COMSAP was developed. From the obtained results, we have observed that with coarse meshes, semiloof shell elements present better results, and it is especially effective in the case of thin plates and shells.