float.h中的C標準庫的頭文件包含了一組浮點值相關(guān)的各種平臺相關(guān)的常數(shù)。這些常量是由ANSI C允許更多的可移植程序提出。之前檢查所有的常量,它是很好的理解浮點數(shù)是由以下四個元素:
組件 | 組件說明 |
---|---|
S | sign ( +/- ) |
b | base or radix of the exponent representation, 2 for binary, 10 for decimal, 16 for hexadecimal, and so on... |
e | exponent, an integer between a minimum emin and a maximum emax. |
p | precision, the number of base-b digits in the significand |
上述4個組成部分的基礎上,一個浮點將它的值,如下所示:
floating-yiibai = ( S ) p x be or floating-yiibai = (+/-) precision x baseexponent
下面的值是特定于實現(xiàn)定義#define指令,但這些數(shù)值可能沒有任何比這里給出低。注意,F(xiàn)LT是指為float類型在所有情況下,DBL是指double番,而LDBL指 long double。
宏 | 描述 |
---|---|
FLT_ROUNDS |
Defines the rounding mode for floating yiibai addition and it can have any of the following values:
|
FLT_RADIX 2 | This defines the base radix representation of the exponent. A base-2 is binary, base-10 is the normal decimal representation, base-16 is Hex. |
FLT_MANT_DIG DBL_MANT_DIG LDBL_MANT_DIG |
These macros define the number of digits in the number (in the FLT_RADIX base). |
FLT_DIG 6 DBL_DIG 10 LDBL_DIG 10 |
These macros define the maximum number decimal digits (base-10) that can be represented without change after rounding. |
FLT_MIN_EXP DBL_MIN_EXP LDBL_MIN_EXP |
These macros define the minimum negative integer value for an exponent in base FLT_RADIX. |
FLT_MIN_10_EXP -37 DBL_MIN_10_EXP -37 LDBL_MIN_10_EXP -37 |
These macros define the minimum negative integer value for an exponent in base 10. |
FLT_MAX_EXP DBL_MAX_EXP LDBL_MAX_EXP |
These macros define the maximum integer value for an exponent in base FLT_RADIX. |
FLT_MAX_10_EXP +37 DBL_MAX_10_EXP +37 LDBL_MAX_10_EXP +37 |
These macros define the maximum integer value for an exponent in base 10. |
FLT_MAX 1E+37 DBL_MAX 1E+37 LDBL_MAX 1E+37 |
These macros define the maximum finite floating-yiibai value. |
FLT_EPSILON 1E-5 DBL_EPSILON 1E-9 LDBL_EPSILON 1E-9 |
These macros define the least significant digit representable. |
FLT_MIN 1E-37 DBL_MIN 1E-37 LDBL_MIN 1E-37 |
These macros define the minimum floating-yiibai value.. |
下面的例子演示了如何使用幾個在float.h文件中定義的常量。
#include <stdio.h> #include <float.h> int main() { printf("The maximum value of float = %.10e ", FLT_MAX); printf("The minimum value of float = %.10e ", FLT_MIN); printf("The number of digits in the number = %.10e ", FLT_MANT_DIG); }
讓我們編譯和運行上面的程序,這將產(chǎn)生以下結(jié)果:
The maximum value of float = 3.4028234664e+38 The minimum value of float = 1.1754943508e-38 The number of digits in the number = 7.2996655210e-312