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) 7.5 PLURAL libraries 7.6 Graded commutative algebras (SCA) 7.7 LETTERPLACE 7.8 Functions (letterplace) 7.9 Mathematical background (letterplace) 7.10 LETTERPLACE libraries 7.11 Release Notes (letterplace)