What does the exponent represent?

The exponent is a signed integer giving the power of 2 that the mantissa is multiplied by. A positive exponent moves the binary point right and a negative exponent moves it left.

Why are the mantissa and exponent usually held in two's complement?

Two's complement lets one adder handle positive and negative values without extra logic. A single representation of zero also avoids ambiguity.

How does the number of mantissa bits affect a floating point format?

More mantissa bits give greater precision, so more significant figures are kept. Precision is unaffected by the exponent, which only sets the magnitude.

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Data Types, Characters and Floating Point

Floating point form: mantissa and exponent

3 things to know
Component 2

Overview

Two parts of a floating point number and normalisation of a floating point number.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What are the two parts of a floating point number?

Key term

Why is the form called floating point?

Key term

What does the mantissa represent in a binary floating point number?

Questions from this subtopic

Each one with the model answer underneath.

1
What are the two parts of a floating point number?
Model answer
A floating point number is made of a mantissa and an exponent. The mantissa holds the significant digits and the exponent fixes the position of the binary point.
2
Why is the form called floating point?
Model answer
The binary point is not fixed in one column but moves according to the exponent. A single format can therefore hold very large and very small values.
3
What does the mantissa represent in a binary floating point number?
Model answer
The mantissa is a signed binary fraction, normally with the binary point just after the sign bit. The mantissa value lies between −1 and +1.
4
What does the exponent represent?
Model answer
The exponent is a signed integer giving the power of 2 that the mantissa is multiplied by. A positive exponent moves the binary point right and a negative exponent moves it left.
5
Why are the mantissa and exponent usually held in two's complement?
Model answer
Two's complement lets one adder handle positive and negative values without extra logic. A single representation of zero also avoids ambiguity.
6
How does the number of mantissa bits affect a floating point format?
Model answer
More mantissa bits give greater precision, so more significant figures are kept. Precision is unaffected by the exponent, which only sets the magnitude.

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