# 8-bit floating-point representation

I'm studying about representing fractional numbers as floating-point values. It is going to be an 8-bit representation. Somewhere in the text, it is said that: "We use the first bit to represent the sign (1 for negative, 0 for positive), the next four bits for the sum of 7 and the actual exponent (we add 7 to allow for negative exponents), and the last three bits for the mantissa's fractional part"

Now the question is: Why "7" -and not another value- must be added to the actual exponent ?

• Welcome to CS.SE! The text hints at why, in the parenthetical. Incidentally, if you don't understand the explanation in one text, it's often helpful to search for a different explanation of the subject. There are many resources on floating point. – D.W. Mar 11 '16 at 11:55
• So, why 7 should be added? – Peter Mar 11 '16 at 12:01
• If you've understood the answer to your first question, I encourage you to edit your post to show what you do understand. – D.W. Mar 11 '16 at 12:04