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The COBOL DFA Tool: A Work in Progress

The COBOL DFA Tool: A Work in Progress. Ronald Finkbine, Ph.D. Indiana University Southeast New Albany, IN rfinkbine@ius.edu. Introduction. Software Complexity Programmer Understandability Maintainability Reduction by Tools Reduction by Technique. Deterministic Finite Automaton.

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The COBOL DFA Tool: A Work in Progress

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  1. The COBOL DFA Tool:A Work in Progress Ronald Finkbine, Ph.D.Indiana University SoutheastNew Albany, INrfinkbine@ius.edu ISECON 2003

  2. Introduction • Software Complexity • Programmer Understandability • Maintainability • Reduction by Tools • Reduction by Technique ISECON 2003

  3. Deterministic Finite Automaton • Finite State Machine • Abstract State Machine • Moore Machine • Mealy Machine • Set of states • Set of transitions • Single input ISECON 2003

  4. Elementary DFA • Accepts language a*b • Incomplete ISECON 2003

  5. Benefits of DFA • High-reliability • Is DFA a proof or show? • Mathematics is a modeling method • Proofs are social constructs • Diagrammatics ISECON 2003

  6. DFA File Sample • DFACONTROL • START A • ACCEPT B • OUTPUT-COBOL "DFA.COB" • INPUT-DATA "IN.TXT" • OUTPUT-DATA "OUT.TXT" • DFACODE • F-BEGIN • DISPLAY “IN F_BEGIN” • F-END • DISPLAY “IN F_END” • DFASTATE • A A "a" F-Begin • A B "b" F-End ISECON 2003

  7. Produced COBOL Sample • F-BEGIN. • DISPLAY ‘IN F-BEGIN’ • F-END. • DISPLAY ‘IN F-END’ • MAIN-PARAGRAPH. • MOVE ‘A’ TO CURRENT-STATE • MOVE ‘NO ‘ TO INPUT-EMPTY • READ INPUT-CHAR AT END MOVE ‘YES’ TO INPUT-EMPTY • PERFORM UNTIL INPUT-EMPTY = ‘YES’ • IF CURRENT-STATE = ‘A’ AND INPUT-CHAR = ‘a’ THEN • MOVE ‘A’ TO CURRENT-STATE • PERFORM F-BEGIN • ELSE IF CURRENT-STATE = ‘A’ AND INPUT-CHAR = ‘b’ THEN • MOVE ‘B’ TO CURRENT-STATE • PERFORM F-END • ELSE IF NOT ((INPUT-CHAR = ‘a’) OR (INPUT-CHAR = ‘b’)) THEN • MOVE ‘ERROR’ TO CURRENT-STATE • DISPLAY “BAD INPUT CHARACTER” • ELSE • MOVE ‘ERROR’ TO CURRENT-STATE • DISPLAY “UNSPECIFIED STATE/TRANSITION” • ENDIF • READ INPUT-CHAR AT END MOVE ‘YES’ TO INPUT-EMPTY • END-PERFORM • IF CURRENT-STATE = ‘B’ THEN • DISPLAY ‘ACCEPTED’ • ELSE • DISPLAY ‘REJECTED’ • ENDIF ISECON 2003

  8. Fox, Grain, Chicken Problem • A man is crossing a river on the way to market with a chicken, a bag of grain and a fox. If left unattended the fox will eat the chicken, and the chicken will eat the grain. The boat will only hold the man and one of these at a time. Your task is to work out a sequence of crossings that will affect a safe transfer of the man, the fox, the chicken and the grain safely across the river. ISECON 2003

  9. Fox, Chicken, Grain Solution ISECON 2003

  10. Text: CeFCGeC • Translating into English, the input string represents: • Man and chicken cross river • Man returns with empty boat • Man and fox cross river • Man returns with chicken • Man and grain cross river • Man returns with empty boat • Main and chicken cross river ISECON 2003

  11. Summary • COBOL tool to input/produce DFA • Vending machine assignment • Not controlled experiment • Intro to DFA Design methodology ISECON 2003

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