29 lines
932 B
Markdown
29 lines
932 B
Markdown
# Chapter 5. Bit manipulation
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## 5.1. Two's complement and negative numbers
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Positive numbers are represented as themselves, negative numbers as the two's complement of its absolute value, with a 1 in its sign bit, indicating it's negative.
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The two's complement of an N-bit number (N: \# bits used for the number, excluding the sign bit), is the complement of the number with respect to 2<sup>N</sup>.
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The binary representation of -K as a N-bit number is concat(1, 2<sup>N-1</sup> - K).
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## 5.2. Arithmetic vs. Logical right shift
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Arithmetic right shift: division by two. Logical right shift: 'shifting the bits'.
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### 5.2.1. Logical shift
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Indicated with a >>> operator, all bits are shifted, sign bit too.
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* -75: **1**0110101
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* 90: **0**1011010
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### 5.2.2. Arithmetic shift
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The sign bit is kept, and all bits (sign bit too) are shifted.
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* -75: **1**0110101
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* -38: **1**1011010
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## 5.3. Common bit tasks: getting and setting |