MySQL 5.5: declare a column has value in a range -

i believe basic question data type in mysql can't find answer ...

i have column defined this: cd4: max n4, r

n4 means column hold numeric values has 4 numbers , r (required) means can't null

max n4 means column hold value 4 characters or less.

how can declare such column?

i think if declare column be: cd4 mediumint(4) not null value stored in column must have 4 character right?