How does 0x12.2P2 equal 72.5?
I know that the value following the P, called the binary exponent, indicates the power-of-two by which the number is multiplied?
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The Guy with The Hat
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0x12.2P2 is 0x122 / 1610 * 22
- 0x122 = 29010
- divided by 1610 = 18.12510
- multiplied by 22 leads to 72.510
More formally (?), for the part before the P, you can use this very classic conversion table:
decimal point here ▼
+-----+-----+-----+-----+-+-----+-----+-----+
| 16³ | 16² | 16¹ | 16⁰ | | 16⁻¹| 16⁻²| 16⁻³|
+-----------------------------------------+
| | | 1 | 2 |.| 2 | | |
+-----+-----+-----+-----+-+-----+-----+-----+
So 0x12.2 is 1⨯16¹+2x16⁰+2⨯16⁻¹ = 18.125
Sylvain Leroux
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I think you mean 290 instead of 190. – Eran Globen Sep 07 '14 at 16:44
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1@Eran Damn! Stupid typo... Thank you for pointing that out ! – Sylvain Leroux Sep 07 '14 at 16:58
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I get 18.125 for dividing 290 by 16 in decimal, and 72.52 for multiplying 18.13 by 4. I recommend replacing "18.13" with "18.125" in both places where it appears. – Patricia Shanahan Sep 07 '14 at 19:06
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1@Patricia Thank you. I didn't even noticed than my desktop calculator has rounded the result. How silly am I this evening... – Sylvain Leroux Sep 07 '14 at 19:18