Hex -> Integer

Вариант 1:

var
  i: integer
  s: string;
begin
  s := '$' + ThatHexString;
  i := StrToInt(a);
end;

Вариант 2:

const HEX: array['A'..'F'] of INTEGER = (10, 11, 12, 13, 14, 15);
var str: string;
    Int, i: integer;
begin
  READLN(str);
  Int := 0;
  for i := 1 to Length(str) do
    if str[i] < 'A' then
      Int := Int * 16 + ORD(str[i]) - 48
    else
      Int := Int * 16 + HEX[str[i]];
  WRITELN(Int);
  READLN;
end.