display an int with 1 or 2 digits as a 2 digit number?

If I have an integer with 1 or 2 digits e.g. 1 or 9 or 11 how can I display it as two digits?

i.e.
01, 09 and 11

There must be a function of something instead of inspecting the int and adding a '0' to the begining of it if it is only 1 digit long

Thanks