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Since the discussion above considers only whole numbers, why is this the
fixed point worksheet? Well, technically the binary point is to the right
of the least significant bit (digit) in the representations shown above.
Furthermore, you can express a subset of the rational numbers by moving
the binary point to the left in any of the above representations.
Note that in fixed point notations,
the position of the binary point is assumed-that is, no space
needs to be devoted to it because the number of places or digits to the
right of the binary point is predefined-literally, fixed.
For example, a 32-bit fixed point number might have 8 bits
representing the binary fractional part of the number,
and the remaining 24 bits will be the integer part. The only difference
from the previous expressions is that, like in base 10, the first position
to the right of the binary point corresponds to ; the next is
and so on, down to for 8 bits. We don't see fixed
point like this very often anymore, because with the exception of machines
with fixed accuracy (such as cash registers, where the the smallest
difference between values is 1 cent.
regardless, as long as you know where the binary point is, and it
never moves, technically you are dealing with fixed point notation.
Next: Conversion: Signed Magnitude to
Up: numbers
Previous: Sign(ed) 2's Complement
MM Hugue
2004-09-08