The operations and symbols that are allowed are: the four arithmetic operations (+,x,-,/), concatenation (44 is ok and uses up two 4's), decimal points (using 4.4 is ok), powers (using 44 is ok), square roots, factorials (using 4! is ok), and overbars for indicating repeating digits (e.g., writing .4 with an overbar would be a way of expressing 4/9). Ordinary use of parentheses are allowed. No digits other than 4 are allowed.
This problem is sometimes called the four fours problem. It was popularized by Martin Gardner, among others.
So... Take out your pen and paper... find all the possibilities from 1 to 100. Write your answers in the comment box.