langs a-z

Task/Caesar-cipher/Run-BASIC/caesar-cipher.run

@@ -0,0 +1,21 @@
+input "Gimme a ofset:";ofst       ' set any offset you like
+
+a$ = "Pack my box with five dozen liquor jugs"
+print " Original: ";a$
+a$ = cipher$(a$,ofst)
+print "Encrypted: ";a$
+print "Decrypted: ";cipher$(a$,ofst+6)
+
+FUNCTION cipher$(a$,ofst)
+for i = 1 to len(a$)
+  aa$   = mid$(a$,i,1)
+  code$ = " "
+  if aa$ <> " " then
+    ua$   = upper$(aa$)
+    a     = asc(ua$) - 64
+    code$ = chr$((((a mod 26) + ofst) mod 26) + 65)
+    if ua$ <> aa$ then code$ = lower$(code$)
+  end if
+  cipher$ = cipher$;code$
+next i
+END FUNCTION