Literals that start with `0x` are hexadecimal integers. (base 16)

The number `0x6400` is `25600`.

    6 * 16^3 + 4 * 16^2 = 25600

For an example including letters (also used in hexadecimal notation where A = 10, B = 11 ... F = 15)

The number `0x6BF0` is `27632`.
 
    6 * 16^3 + 11 * 16^2 + 15 * 16^1 = 27632
    24576    + 2816      + 240       = 27632



In C and languages based on the C syntax, the prefix `0x` means hexadecimal (base 16).

Thus, 0x400 = 4&amp;times;(16&lt;sup&gt;2&lt;/sup&gt;) + 0&amp;times;(16&lt;sup&gt;1&lt;/sup&gt;) + 0&amp;times;(16&lt;sup&gt;0&lt;/sup&gt;) = 4&amp;times;((2&lt;sup&gt;4&lt;/sup&gt;)&lt;sup&gt;2&lt;/sup&gt;) = 2&lt;sup&gt;2&lt;/sup&gt; &amp;times; 2&lt;sup&gt;8&lt;/sup&gt; = 2&lt;sup&gt;10&lt;/sup&gt; = 1024, or one binary K.

And so 0x6400 = 0x4000 + 0x2400 = 0x19&amp;times;0x400 = 25K


It&#39;s a hexadecimal number.

&gt; 0x6400 translates to 4*16^2 + 6*16^3 = 25600


**SIMPLE**

It&#39;s a prefix to indicate the number is in hexadecimal rather than in some other base. The C programming language uses it to tell compiler.

**Example :**

`0x6400` translates to `6*16^3 + 4*16^2 + 0*16^1 +0*16^0 = 25600.` When compiler reads `0x6400`, It understands the number is hexadecimal with the help of 0x term. Usually we can understand by `(6400)16 or (6400)8` or any base ..

Hope Helped in some way.

Good day,


The numbers starting with `0x` are hexadecimal (base 16).`0x6400` represents `25600`. 

To convert,
 
- multiply the last digit times 1 
- add second-last digit times 16 (16^1) 
- add third-last digit times 256 (16^2)
- add fourth-last digit times 4096 (16^3)
- ...and so on 

The factors 1, 16, 256, etc. are the increasing powers of 16.

    0x6400 = (0*1) + (0*16^1) + (4*16^2) + (6*16^3) = 25600 

or

    0x6400 = (0*1) + (0*16) + (4*256) + (6*4096) = 25600 

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<pre><code class="hljs language-ini">const int shared_segment_size = 0x6400;
</code></pre>
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Content Type	Original Author	Original Content on Stackoverflow
Question	Terry Li	View Question on Stackoverflow
Solution 1 - C	Mysticial	View Answer on Stackoverflow
Solution 2 - C	Cheers and hth. - Alf	View Answer on Stackoverflow
Solution 3 - C	knittl	View Answer on Stackoverflow
Solution 4 - C	loyola	View Answer on Stackoverflow
Solution 5 - C	Sithu	View Answer on Stackoverflow

What do numbers using 0x notation mean?

C Problem Overview

C Solutions

Solution 1 - C

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Solution 3 - C

Solution 4 - C

Solution 5 - C

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