Initial data commit

Task/Caesar-cipher/XBasic/caesar-cipher.basic

@@ -0,0 +1,56 @@
+PROGRAM "caesarcipher"
+VERSION "0.0001"
+
+DECLARE FUNCTION Entry()
+INTERNAL FUNCTION Encrypt$(p$, key%%)
+INTERNAL FUNCTION Decrypt$(p$, key%%)
+
+FUNCTION Entry()
+  txt$ = "The five boxing wizards jump quickly"
+  key%% = 3
+  PRINT "Original:  "; txt$
+  enc$ = Encrypt$(txt$, key%%)
+  PRINT "Encrypted: "; enc$
+  PRINT "Decrypted: "; Decrypt$(enc$, key%%)
+END FUNCTION
+
+FUNCTION Encrypt$(p$, key%%)
+  e$ = p$ ' In order to avoid iterative concatenations
+  FOR i = 0 TO LEN(p$) - 1
+    t@@ = p${i} ' or (slower) t@@ = ASC(p$, i + 1)
+    SELECT CASE TRUE
+      CASE (t@@ >= 'A') AND (t@@ <= 'Z'):
+        t@@ = t@@ + key@@
+        IF t&& > 'Z' THEN
+          t@@ = t@@ - 26
+        END IF
+      CASE (t@@ >= 'a') AND (t@@ <= 'z'):
+        t@@ = t@@ + key%%
+        IF t@@ > 'z' THEN
+          t@@ = t@@ - 26
+        END IF
+    END SELECT
+    e${i} = t@@
+  NEXT i
+END FUNCTION e$
+
+FUNCTION Decrypt$(p$, key%%)
+  e$ = p$ ' In order to avoid iterative concatenations
+  FOR i = 0 TO LEN(p$) - 1
+    t@@ = p${i} ' or (slower) t@@ = ASC(p$, i + 1)
+    SELECT CASE TRUE
+      CASE (t@@ >= 'A') AND (t@@ <= 'Z'):
+        t@@ = t@@ - key%%
+        IF t@@ < 'A' THEN
+          t@@ = t@@ + 26
+        END IF
+      CASE (t@@ >= 'a') AND (t@@ <= 'z'):
+        t@@ = t@@ - key%%
+        IF t@@ < 'a' THEN
+          t@@ = t@@ + 26
+        END IF
+    END SELECT
+    e${i} = t@@
+  NEXT i
+END FUNCTION e$
+END PROGRAM