CHAR FUNC Shift(CHAR c BYTE code)
  CHAR base

  IF c>='a AND c<='z THEN
    base='a
  ELSEIF c>='A AND c<='Z THEN
    base='A
  ELSE
    RETURN (c)
  FI
  c==+code-base
  c==MOD 26
RETURN (c+base)

PROC Encrypt(CHAR ARRAY in,out BYTE code)
  INT i

  out(0)=in(0)
  FOR i=1 TO in(0)
  DO
    out(i)=Shift(in(i),code)
  OD
RETURN

PROC Decrypt(CHAR ARRAY in,out BYTE code)
  Encrypt(in,out,26-code)
RETURN

PROC Test(CHAR ARRAY in BYTE code)
  CHAR ARRAY enc(256),dec(256)

  PrintE("Original:") PrintE(in)
  Encrypt(in,enc,code)
  PrintF("Encrypted code=%B:%E",code) PrintE(enc)
  Decrypt(enc,dec,code)
  PrintF("Decrypted code=%B:%E",code) PrintE(dec)
  PutE()
RETURN

PROC Main()
  Test("The quick brown fox jumps over the lazy dog.",23)
  Test("The quick brown fox jumps over the lazy dog.",5)
RETURN