const
   MAXSTR = 128;

   LORAD  = 2;
   HIRAD  = 16;

   MAXB   = 16;   { number of bytes in a number (16 is probably max). }
   MAXBIT = 255;  { MAXB * 8 - 1 }

   NUMS : string[36] = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';

type
   char_set = set of char;
   bits     = set of 0..MAXBIT;

const
   NUMDIGIT   : char_set = ['0'..'9', 'A'..'F', 'a'..'f'];
   WHITESPACE : char_set = [' '];
   OPCHARS    : char_set = ['+', '-', '*', '/', '%', '&', '|', '^', '~', '!'];
   PARENS     : char_set = ['(', ')'];

   neg_one    : bits     = [0..MAXBIT];

type
   str      = string[MAXSTR];
   sign     = -1..1;

   num_arr  = array[1..MAXB] of byte;
   number   = record
              case boolean of
                 false : (n : num_arr;
                          s : sign);
                 true  : (b : bits);
              end;

var
   zero_n   : number;

   num, ans : str;

   in_rad,
   out_rad  : integer;
   inst     : char;
   args     : str;

   voidi    : integer;
   voids    : str;