CHARACTER_ARITHMETIC:
  C version

  c1 = a (character) = 97 (integer)
  c2 = b (character) = 98 (integer)
  c3 = c (character) = 99 (integer)
  c4 = d (character) = 100 (integer)
  c5 = z (character) = 122 (integer)
  c6 = A (character) = 65 (integer)
  c7 = & (character) = 38 (integer)
  c8 = 7 (character) = 55 (integer)

We can capitalize a lower case letter by adding A-a to it!

  a+A-a = A
  b+A-a = B
  c+A-a = C
  d+A-a = D

We can average two characters

  1/2(a+c)=b
  1/2(a+z)=m