We present the properties of the C-parameter as an event-shape variable. We calculate the coupling constants in the perturbative and also in the non-perturbative parts of the QCD theory, using the dispersive as wellas the shape function models. By fitting the corresponding theoretical predictions to our data, we find $\alpha_{s}(M_{Z^{0}} ) = 0.117 \pm 0.014$ and $\alpha_{0}(\mu_{I} ) = 0.491 \pm 0.043$ for dispersive model and $\alpha_{ s}(M_{Z^{0}} ) = 0.124 \pm 0.015$ and $\lambda_{1} = 1.234 \pm 0.052$ for the shape function model. Our results are consistent with the world average value of $\alpha_{s}(M_{Z^{0}} ) = 0.118 \pm 0.002$. All these features are explained in the main text.