title: Howto encode/decode alphanumeric string to unsigned integer with defined set of chars
body: <p>I have this charset  = [0123456789A BCDEFGH IJKLMNOPRTUVWZX]
  I need to know howto convert any unsigned int to this in gcc/C</p>
  
  <p>number - string
    02      = 2 
    10      = A
    20      = K
    30      = W
    1500    = ???
    8534    = ???</p>