Create Fibonacci Sequence.cbl

Signed-off-by: Dillon Depeel <dillondepeel@hotmail.com>

Fibonacci Sequence.cbl

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+IDENTIFICATION DIVISION.
+       PROGRAM-ID. FIB.
+       DATA DIVISION.
+       FILE SECTION.
+       WORKING-STORAGE SECTION.
+       01  N0             BINARY-C-LONG VALUE 0.
+       01  N1             BINARY-C-LONG VALUE 1.
+       01  SWAP           BINARY-C-LONG VALUE 1.
+       01  RESULT         PIC Z(20)9.
+       01  I              BINARY-C-LONG VALUE 0.
+       01  I-MAX          BINARY-C-LONG VALUE 0.
+       01  LARGEST-N      BINARY-C-LONG VALUE 92.
+
+       PROCEDURE DIVISION.
+      *>  THIS IS WHERE THE LABELS GET CALLED
+           PERFORM MAIN
+           PERFORM ENDFIB
+           GOBACK.
+
+      *>  THIS ACCEPTS INPUT AND DETERMINES THE OUTPUT USING A EVAL STMT
+       MAIN.
+            DISPLAY "ENTER N TO GENERATE THE FIBONACCI SEQUENCE"
+            ACCEPT I-MAX.
+
+            EVALUATE TRUE
+              WHEN I-MAX > LARGEST-N
+                 PERFORM INVALIDN
+
+              WHEN I-MAX > 2
+                 PERFORM CASEGREATERTHAN2
+
+              WHEN I-MAX = 2
+                 PERFORM CASE2
+
+              WHEN I-MAX = 1
+                 PERFORM CASE1
+
+              WHEN I-MAX = 0
+                 PERFORM CASE0
+
+              WHEN OTHER
+                 PERFORM INVALIDN
+
+            END-EVALUATE.
+
+            STOP RUN.
+
+
+
+       *>  THE CASE FOR WHEN N = 0
+       CASE0.
+           MOVE N0 TO RESULT.
+           DISPLAY RESULT.
+
+      *>  THE CASE FOR WHEN N = 1
+       CASE1.
+           PERFORM CASE0
+           MOVE N1 TO RESULT.
+           DISPLAY RESULT.
+
+      *>  THE CASE FOR WHEN N = 2
+       CASE2.
+           PERFORM CASE1
+           MOVE N1 TO RESULT.
+           DISPLAY RESULT.
+
+      *>  THE CASE FOR WHEN N > 2
+       CASEGREATERTHAN2.
+           PERFORM CASE1
+           PERFORM VARYING I FROM 1 BY 1 UNTIL I = I-MAX
+                   ADD N0 TO N1 GIVING SWAP
+                   MOVE N1 TO N0
+                   MOVE SWAP TO N1
+                   MOVE SWAP TO RESULT
+                   DISPLAY RESULT
+            END-PERFORM.
+
+      *>  PROVIDE ERROR FOR INVALID INPUT
+       INVALIDN.
+           DISPLAY 'INVALID N VALUE. THE PROGRAM WILL NOW END'.
+
+      *>  END THE PROGRAM WITH A MESSAGE
+       ENDFIB.
+           DISPLAY "THE PROGRAM HAS COMPLETED AND WILL NOW END".
+
+       END PROGRAM FIB.