Several petrological processes, such as (1) fractional crystallization (FC), (2) combined and decoupled fractional crystallization and assimilation (AFC and FCA), and (3) mixing processes, which modify the geochemical composition of the magma, are graphically programmed using Microsoft (R) Excel (c) spreadsheet on the basis of differentiation equations. The FC-AFC-FCA and mixing modeler is an interactive program that models the consequent theoretical vectors of FC, AFC, FCA, and mixing processes, which are frequently used in modern petrology. The program enables the user to export outputs of linear- or logarithmic-scaled bivariate diagrams and also rare earth elements (REE)- and multi-element spider diagrams of the modeling results. It also plots some classification diagrams as well as bivariate Harker variation diagrams. Because the program is interactive in nature, changes in any parameters are simultaneously updated onto all diagrams. (C) 2009 Elsevier Ltd. All rights reserved.