# 2.4.2 浮点型

浮点型数字采用科学计数法。你可以把浮点数当成有小数的十进制数字。浮点数有效数字的位数和范围取决于你的机器。Emacs 使用 C 内部的 double 数据类型储存数据，此外内部记录使用二进制, 而非十进制。

浮点型数字的打印表示包含小数点, 或指数形式, 或两者都包含。比如, '1500.0', '+15e2', '+1500000e-3', 以及 '.15e4' 是 **浮点数** 1500 的五种打印表示，它们都是等价的。


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