Аннотация:Ever since its invention and initial description in 1652, Blaise Pascal's adding machine has been the subject of numerous studies and publications (D. Diderot and J.L. d'Alembert, 1751). However, when compiling and systematically analyzing the literature, a rather diffuse image emerges. For one thing, the method of subtraction is not accurately described. The article attempts to find out how one could have used Pascal's Adding Machine (PAM), had it ever functioned properly. In addition, this is an attempt to provide a comprehensive functional description of the machine.