The present article shows that the letters of the Modern Roman Alphabet have an internal structure that is highly systematic in both inner-graphematic and functional-phonological terms. The framework of analysis is Optimality Theory. This approach is congenial for the data at issue as many apparently unmotivated exceptions are optimal choices among competing candidates that are evaluated by violable ranked constraints. The results of the present investigation corroborate a branching correspondence model in which general modality-independent constraints such as dependency, compositionality, markedness and iconism are shown to have independent modality-specific instantiations in speech and writing with bidirectional correspondences serving as functional links across modalities.