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copied!<p>I have included code which produces hexadecimal output that I think may help you understand floating-point numbers. Here is an example:</p> <blockquote> <p>double: 00 00 A4 0F 0D 4B 72 42 (1257096936000.000000) (+0x1.24B0D0FA40000 x 2^40)</p> </blockquote> <p>From my code example below, it should become obvious to you how to output the bits. Cast the double's address to <code>unsigned char *</code> and output the bits of <code>sizeof(double)</code> chars.</p> <p>Since I want to output the exponent and significand (and sign bit) of a floating-point number, my example code digs into the bits of the IEEE-754 standard representation for 64-bit 'double precision' floating pointing point in radix 2. Therefore I do not use <code>sizeof(double)</code> other than to verify that the compiler and I agree that <code>double</code> means a 64-bit float.<br></p> <p>If you would like to output the bits for a floating-point number of any type, do use <code>sizeof(double)</code> rather than <code>8</code>.</p> <pre><code>void hexdump_ieee754_double_x86(double dbl) { LONGLONG ll = 0; char * pch = (char *)&ll; int i; int exponent = 0; assert(8 == sizeof(dbl)); // Extract the 11-bit exponent, and apply the 'bias' of 0x3FF. exponent = (((((char *)&(dbl))[7] & 0x7F) &lt;&lt; 4) + ((((char *)&(dbl))[6] & 0xF0) &gt;&gt; 4) & 0x7FF) - 0x3FF; // Copy the 52-bit significand to an integer we will later display for (i = 0; i &lt; 6; i ++) *pch++ = ((char *)&(dbl))[i]; *pch++ = ((char *)&(dbl))[6] & 0xF; printf("double: %02X %02X %02X %02X %02X %02X %02X %02X (%f)", ((unsigned char *)&(dbl))[0], ((unsigned char *)&(dbl))[1], ((unsigned char *)&(dbl))[2], ((unsigned char *)&(dbl))[3], ((unsigned char *)&(dbl))[4], ((unsigned char *)&(dbl))[5], ((unsigned char *)&(dbl))[6], ((unsigned char *)&(dbl))[7], dbl); printf( "\t(%c0x1.%05X%08X x 2^%d)\n", (((char *)&(dbl))[6] & 0x80) ? '-' : '+', (DWORD)((ll & 0xFFFFFFFF00000000LL) &gt;&gt; 32), (DWORD)(ll & 0xFFFFFFFFLL), exponent); } </code></pre> <p>Nota Bene: The significand is displayed as a hexadecimal fraction ("0x1.24B0D0FA40000") and the exponent is display as decimal ("40"). For me, this was an intuitive way to display the floating-point bits.</p>

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