June 2018 Update

Task/Caesar-cipher/COBOL/caesar-cipher-2.cobol

@@ -0,0 +1,86 @@
+       >>SOURCE FORMAT IS FREE
+PROGRAM-ID. caesar-cipher.
+
+ENVIRONMENT DIVISION.
+CONFIGURATION SECTION.
+REPOSITORY.
+    FUNCTION encrypt
+    FUNCTION decrypt
+    .
+DATA DIVISION.
+WORKING-STORAGE SECTION.
+01  plaintext                 PIC X(50).
+01  offset                    PIC 99.
+
+01  encrypted-str             PIC X(50).
+
+PROCEDURE DIVISION.
+    DISPLAY "Enter a message to encrypt: " NO ADVANCING
+    ACCEPT plaintext
+    DISPLAY "Enter the amount to shift by: " NO ADVANCING
+    ACCEPT offset
+
+    MOVE FUNCTION encrypt(offset, plaintext) TO encrypted-str
+    DISPLAY "Encrypted: " encrypted-str
+    DISPLAY "Decrypted: " FUNCTION decrypt(offset, encrypted-str)
+    .
+END PROGRAM caesar-cipher.
+
+
+FUNCTION-ID. encrypt.
+
+DATA DIVISION.
+LOCAL-STORAGE SECTION.
+01  i                         PIC 9(3).
+
+01  a                         PIC 9(3).
+
+LINKAGE SECTION.
+01  offset                    PIC 99.
+01  str                       PIC X(50).
+
+01  encrypted-str             PIC X(50).
+
+PROCEDURE DIVISION USING offset, str RETURNING encrypted-str.
+    MOVE str TO encrypted-str
+    PERFORM VARYING i FROM 1 BY 1 UNTIL i > FUNCTION LENGTH(str)
+        IF encrypted-str (i:1) IS NOT ALPHABETIC OR encrypted-str (i:1) = SPACE
+            EXIT PERFORM CYCLE
+        END-IF
+
+        IF encrypted-str (i:1) IS ALPHABETIC-UPPER
+            MOVE FUNCTION ORD("A") TO a
+        ELSE
+            MOVE FUNCTION ORD("a") TO a
+        END-IF
+
+        MOVE FUNCTION CHAR(FUNCTION MOD(FUNCTION ORD(encrypted-str (i:1))
+                - a + offset, 26) + a)
+            TO encrypted-str (i:1)
+    END-PERFORM
+    .
+END FUNCTION encrypt.
+
+
+FUNCTION-ID. decrypt.
+
+ENVIRONMENT DIVISION.
+CONFIGURATION SECTION.
+REPOSITORY.
+    FUNCTION encrypt
+    .
+DATA DIVISION.
+LOCAL-STORAGE SECTION.
+01  decrypt-offset            PIC 99.
+
+LINKAGE SECTION.
+01  offset                    PIC 99.
+01  str                       PIC X(50).
+
+01  decrypted-str             PIC X(50).
+
+PROCEDURE DIVISION USING offset, str RETURNING decrypted-str.
+    SUBTRACT 26 FROM offset GIVING decrypt-offset
+    MOVE FUNCTION encrypt(decrypt-offset, str) TO decrypted-str
+    .
+END FUNCTION decrypt.