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Real floating-point type, usually mapped to an extended precision floating-point number format. Actual properties unspecified. Actual properties unspecified. It can be either x86 extended-precision floating-point format (80 bits, but typically 96 bits or 128 bits in memory with padding bytes ), the non-IEEE " double-double " (128 bits), IEEE ...
The representation has a limited precision. For example, only 15 decimal digits can be represented with a 64-bit real. If a very small floating-point number is added to a large one, the result is just the large one. The small number was too small to even show up in 15 or 16 digits of resolution, and the computer effectively discards it.
For example, a packed decimal value encoded with the bytes 12 34 56 7C represents the fixed-point value +1,234.567 when the implied decimal point is located between the fourth and fifth digits: 12 34 56 7C 12 34.56 7+ The decimal point is not actually stored in memory, as the packed BCD storage format does not provide for it.
The value encoded is (−1) s ×10 q ×c. In both formats the range of possible values is identical, but they differ in how the significand c is represented. In the decimal encoding, it is encoded as a series of p decimal digits (using the densely packed decimal (DPD) encoding).
If a decimal string with at most 6 significant digits is converted to the IEEE 754 single-precision format, giving a normal number, and then converted back to a decimal string with the same number of digits, the final result should match the original string. If an IEEE 754 single-precision number is converted to a decimal string with at least 9 ...
For example, when shifting a 32 bit unsigned integer, a shift amount of 32 or higher would be undefined. Example: If the variable ch contains the bit pattern 11100101 , then ch >> 1 will produce the result 01110010 , and ch >> 2 will produce 00111001 .
The full decimal significand is then obtained by concatenating the leading and trailing decimal digits. The 10-bit DPD to 3-digit BCD transcoding for the declets is given by the following table. b 9 … b 0 are the bits of the DPD, and d 2 … d 0 are the three BCD digits.
Floating-point constants may be written in decimal notation, e.g. 1.23. Decimal scientific notation may be used by adding e or E followed by a decimal exponent, also known as E notation, e.g. 1.23e2 (which has the value 1.23 × 10 2 = 123.0). Either a decimal point or an exponent is required (otherwise, the number is parsed as an integer constant).