4.1.16

Floating Point Addition

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Floating Point Addition

When adding floating point binary numbers, it is important to ensure each number is represented with the same level of precision. This means that the exponents must be the same.

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Addition

  • The example below shows the addition of two normalised 12-bit floating point numbers, with 8-bit mantissas and 4-bit exponents:
    • 0.10110000011 + 0.11100000010
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Matching exponents

  • The first step is to ensure the exponents of the two numbers match, by adding 1 to the exponent of the second number (2) to match that of the first (3).
  • Adding 1 to the exponent of the second number moves the binary point of the mantissa in this number one place to the left:
    • 0.11100000010 \rightarrow 0.01110000011
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Compute the addition

  • The two mantissas can then be added together:
    • 0.1011000 + 0.0111000 = 1.0010000
  • Including the exponent gives 1.00100000011.
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Normalise the result

  • Check that the result is normalised, and move the binary point as necessary.
  • If the binary point gets moved, remember to change the exponent accordingly.

Jump to other topics

1Components of a Computer

2Software & Software Development

3Exchanging Data

4Data Types, Data Structures & Algorithms

5Legal, Moral, Cultural & Ethical Issues

6Elements of Computational Thinking

6.1Thinking Abstractly

6.2Thinking Ahead

6.3Thinking Procedurally

6.4Thinking Logically

6.5Thinking Concurrently

7Problem Solving & Programming

8Algorithms

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