Initial data commit

Task/Caesar-cipher/GFA-Basic/caesar-cipher.basic

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+'
+' Caesar cypher
+'
+OPENW 1 ! Creates a window for handling input/output
+CLEARW 1
+INPUT "string to encrypt ";text$
+INPUT "encryption key    ";key%
+encrypted$=@encrypt$(UPPER$(text$),key%)
+PRINT "Encrypted: ";encrypted$
+PRINT "Decrypted: ";@decrypt$(encrypted$,key%)
+'
+PRINT "(Press any key to end program.)"
+~INP(2)
+CLOSEW 1
+'
+FUNCTION encrypt$(text$,key%)
+  LOCAL result$,i%,c%
+  result$=""
+  FOR i%=1 TO LEN(text$)
+    c%=ASC(MID$(text$,i%))
+    IF c%<ASC("A") OR c%>ASC("Z") ! don't encrypt non A-Z
+      result$=result$+CHR$(c%)
+    ELSE
+      c%=c%+key%
+      IF c%>ASC("Z")
+        c%=c%-26
+      ENDIF
+      result$=result$+CHR$(c%)
+    ENDIF
+  NEXT i%
+  RETURN result$
+ENDFUNC
+'
+FUNCTION decrypt$(text$,key%)
+  RETURN @encrypt$(text$,26-key%)
+ENDFUNC