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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.
Type Explanation Minimum size (bits) Format specifier Range Suffix for decimal constants bool: Boolean type, added in C23.: 1 (exact) %d [false, true]char: Smallest addressable unit of the machine that can contain basic character set.
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.
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).
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).
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.
BCD numbers can be represented in two ways in integer registers: packed decimal and unpacked decimal. Packed (4 bits) In packed decimal representation a decimal digit is stored in one nibble. The values 10 to 15 are not used. [2] Unpacked (8 bits) In unpacked decimal representation a decimal digit is stored in one byte. The values 10 to 255 are ...
The design of floating-point format allows various optimisations, resulting from the easy generation of a base-2 logarithm approximation from an integer view of the raw bit pattern. Integer arithmetic and bit-shifting can yield an approximation to reciprocal square root ( fast inverse square root ), commonly required in computer graphics .