*Error Patterns; *Mathematics Instruction;

This paper is Concerned with the role of meaning and understanding in the acquisition of computational skill in subtraction. Evidence on the syntactic nature of subtraction errors is reviewed, with common "bugi " described. Then, data c011ected from interviews with four children are summarized in terms of their Semantics of concrete representations of the base system, procedures for adding.and subtracting with concrete representations, semantics of the writing code, procedures for written subtraction and'addition, and mapping. Finally, linking syntax and semantics and why mapping works are discuSsed. (MNS) Reproductions supplied by EDRS are the best that,can be made. *. from the original document. U.S. DEPADTMENT OF EDUCATIO