C语言浮点数表示法 / float表示法（浮点数表示方法）
一直不太清楚C语言中浮点数是怎么表示的，这篇文章能回答我的问题👇浮点表示法float 共计32位(4字节)由最高到最低位分别是第31、30、29、......、0位31位是符号位，1表示该数为负，0反之30~23位，一共8位是指数位(-128~127)22~ 0位，一共23位是尾数位后更。。...
一直不太清楚C语言中浮点数是怎么表示的，这篇文章能回答我的问题👇
float 共计32位(4字节)
由最高到最低位分别是第31、30、29、......、0位
31位是符号位，1表示该数为负，0反之
30~23位，一共8位是指数位(-128~127)
22~ 0位，一共23位是尾数位
后更。。
20230816
C语言中的浮点数表示法
浮点数在C语言编程中扮演着重要的角色，尤其是在需要进行科学计算或者处理实数数据时。浮点数允许我们表示小数，它们的精度和范围都比整数类型更大。本文将详细介绍C语言中的浮点数表示法，包括如何声明、初始化和使用浮点数，以及注意事项。
声明和初始化浮点数
在C语言中，我们可以使用float和double关键字来声明浮点数。float通常用于表示单精度浮点数，而double则用于表示双精度浮点数。
float num1;
double num2;
我们还可以在声明的同时初始化浮点数：
float num1 = 3.14f;
double num2 = 3.141592653589793;
注意，如果一个浮点常量后面有f或F后缀，那么它就是float类型。如果没有这些后缀，它就是double类型。
浮点数的精度
在C语言中，float类型通常占用4个字节（32位），而double类型通常占用8个字节（64位）。因此，double类型的浮点数的精度和范围都比float类型的要大。
printf("Size of float: %lu bytes\n", sizeof(float));
printf("Size of double: %lu bytes\n", sizeof(double));
以上代码将分别打印出float和double类型的大小，通常会看到输出结果为：Size of float: 4 bytes 和 Size of double: 8 bytes。
浮点数运算
与整数类似，我们可以对浮点数进行加、减、乘、除等运算。
float num1 = 10.5f, num2 = 3.0f;
printf("num1 + num2 = %.2f\n", num1 + num2);
printf("num1 - num2 = %.2f\n", num1 - num2);
printf("num1 * num2 = %.2f\n", num1 * num2);
printf("num1 / num2 = %.2f\n", num1 / num2);
在上述代码中，%.2f用于指定浮点数的输出格式，其中.2表示保留两位小数。
注意事项
虽然浮点数在处理实数时非常方便，但也存在一些问题。由于浮点数的内部表示方式，有些值可能无法精确表示。例如，0.1无法用二进制浮点数精确表示。因此，在比较浮点数时，我们应该考虑一定的误差范围。
double num1 = 0.1 * 3;
double num2 = 0.3;
if(fabs(num1 - num2) < 1e-10)
printf("num1 and num2 are equal.\n");
else
printf("num1 and num2 are not equal.\n");
在上述代码中，我们使用了fabs函数和一个很小的正数1e-10来判断两个浮点数是否相等。
参考资料
- Kernighan, B. W., & Ritchie, D. M. (1988). The C Programming Language. Prentice-Hall.
- Prata, S. (2013). C Primer Plus. Addison-Wesley.
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