An infinitely differentiable function with compact support: Definition and properties

This is the English translation of my old paper 'Definici\'on y estudio de una funci\'on indefinidamente diferenciable de soporte compacto', Rev. Real Acad. Ciencias 76 (1982) 21-38. In it a function (essentially Fabius function) is defined and given its main properties, including: unicity, interpretation as a probability, partition of unity with its translates, formulas for its $n$-th derivates, rationality of its values at dyadic points, formulas for the effective computation of these values, and some arithmetical properties of these values. Since I need it now for a reference, I have translated it.