We present a practical method for automatic control concept recognition in large, unstructured imperative programs. Control concepts are abstract notions about interactions between control flow, data flow, and computation, eg.\ ``read-process loop''. They are recognized by comparing a language independent abstract program representation against standard implementation plans. Recognition is efficient and scalable because the program representation is hierarchically decomposed by propers (single entry/exit control flow sub-graphs). A recognition experiment using the UNPROG program understander shows the method's performance, the role of proper decomposition, and planfulness in a sample of programs. As an example of the method's applications, we describe how recognized control concepts are used to perform Cobol restructuring with quality not possible with existing syntactic methods.
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1-Dec-1994
Update: 2-Dec-1994