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POneed some clarification Java's bit representation of integers
 

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  1. POneed some clarification Java's bit representation of integers
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    <p>This could be a very basic question. but I want to understand basic concepts clearly first. The question is about the bit representation of integers in java.</p> <p>In Java integers are represented in <code>32-bits</code>. <code>int y = 3</code>; is represented as <code>00000000 00000000 00000000 00000011</code></p> <p>The <code>32nd bit</code> is the signed bit, which is used to indicate the sign (0 if + and 1 if -ve) what I don't understand is how and why the integers are wrapped when signed: example:</p> <pre><code>y —-&gt;00000000 00000000 00000000 00000011 //3 x — &gt; 11111111 11111111 11111111 11111101 // -3 </code></pre> <p>while it should be: <code>10000000 00000000 00000000 00000011 // -3</code></p> <p>when it is <code>3://00000000 00000000 00000000 00000011,</code></p> <p>I could get the decimal value by <code>1^0 + 2 ^1</code>, by looking at the turned on bits</p> <p>when it is <code>-3://11111111 11111111 11111111 11111101</code> I see it is not easy to calculate the the decimal value. if -3 is represented as <code>10000000 00000000 00000000 00000011:</code> using the first bit, I get -ve, and the usual decimal calculation can be done to get 3</p> <p>similarly for the integer max with -ve sign only the 1st and 32nd bit are turned on:</p> <pre><code>-2147483647 —&gt; 10000000 00000000 00000000 00000001 -2 —&gt; 11111111 11111111 11111111 11111110 -1 —&gt; 11111111 11111111 11111111 11111111 </code></pre> <p>I dont understand how to read these bits to get the decimal value or how exactly is -1 represented by turning on all the bits.</p> <p>Thanks for lending help.</p>
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    1. COhttps://en.wikipedia.org/wiki/Two%27s_complement
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    2. COYou have reinvented a representation of signed integers called "sign-magnitude". It works, but if you start doing math with it, it turns out to be less convenient than 2's complement.
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      1. POneed some clarification Java's bit representation of integers
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    3. CO@harold: can you please tell what the reinvention here..it is good for me to unlearn the wrong understandings..
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