Second, most exponents are stored using excess notation, which is another way of representing positive and negative integers. (We have already studied sign-magnitude form and 2's complement.) In excess notation, the representation of a number is the original number plus a certain fixed amount. We will store only 2 decimal digits for our exponents in this chapter and use excess 50 notation. This means that whatever value we see for the exponent, the actual value is that number minus 50. For instance, the speed of light is represented by 1.86×10⁵⁵. In order to discover the true exponent, we subtract 50 off the exponent. To distinguish between exponents that are to be taken at "face value" from those which are stored in excess-50 notation, we will always underline exponents that are excess-50.

The excess value is always halfway between the minimum and the maximum values so that the range of numbers can be equally divided between negatives and positives. If the numbers we use to represent exponents are 00, 01, 02, ... 97, 98, and 99, then halfway would be 50. Thus any number less than 50 represents a negative exponent while any number over 50 represents a positive one. Real computer hardware often uses excess notation, except that the value they add is a power of 2. Thus, if the exponent were stored in 8 bits, 128 would be the excess value, since it is 10000000 and is halfway between 00000000 and 11111111.