signed exponent

基本解释

First, eight bits for the exponent should represent -128 to 127, just like a signed byte.
首先，表示指数的 8 位应该是从 -128 到 127，就像带符号的字节一样。
The exponent is interpreted as a signed integer, allowing negative as well as positive exponents.
作为有符号整数的指数可以有正负之分。
A floating literal consists of an integer part, a decimal point, a fraction part, ane or E, an optionally signed integer exponent, and an optional type suffix.
浮点文字量由整数部分，小数点，小数部分，e 或 E，可选的有符号整数指数，以及可选的类型后缀组成。