SINGULAR has three non-commutative subsystems, handling various classes of associative non-commutative rings: PLURAL, SCA and LETTERPLACE.
7.1 PLURAL 7.2 Data types (plural) 7.3 Functions (plural) 7.4 Mathematical background (plural) 7.8 PLURAL libraries 7.5 Graded commutative algebras (SCA) 7.6 LETTERPLACE 7.7 LETTERPLACE libraries