This report describes TORUS, a computer-based program for elementary school students with learning disabilities which analyzes student work samples in addition and subtraction and provides individual profiles of student misconceptions and weaknesses. Initially, work samples from 236 middle school students with learning disabilities were analyzed by a human expert to assess the relative difficulty of addition and subtraction in terms of number and types of misconceptions and to provide an empirical basis for encoding misconception algorithms into the TORUS program. Pilot test data, construct validity research, and criterion validity studies are described, as are the use of commercial programs as building blocks for sophisticated software and differences between TORUS and the BUGGY program. The 10 most common substraction misconceptions are identified and matched to the sequence of the "Corrective Mathematics Program," a remedial curricula for special education students. Included in the report are a sample TORUS student profile and the following two papers: "A Comparison of TORUS and Human Expert Diagnoses: A Construct Validity Study" (Michael Landes) and "Software Development in Special Education" (John Woodward). (Contains 109 references.) (SW)