V_us and CP violation from kaon decays with the KLOE detector

The KLOE experiment has provided precise measurements of the branching ratio of the main neutral and charged kaon decay modes, of the K_l and the K^± lifetimes, and of the K_l vector and scalar form factors. We present a description of the above measurements and an overall fit of all our data, with particular attention to correlations. These data provide the basis for the determination of the value of the CKM matrix element V_us and a test of the unitarity of the quark mixing matrix. In addition our first measurement of the charge asimmetry in K_S semileptonic decays, A_S, gaves us the possibility to contribute to the knowledge of () and testing the CPT symmetry through the Bell Steinberger relation.