无符号整数比有符号整数更容易让您陷入特定的陷阱。陷阱来自于这样一个事实:虽然上面的1和3是正确的，但这两种类型的整数都可以被赋值到它可以“容纳”的范围之外，并且它将被无声地转换。

unsigned int ui = -1;
signed int si = -1;

if (ui < 0) {
    printf("unsigned < 0\n");
}
if (si < 0) {
    printf("signed < 0\n");
}
if (ui == si) {
    printf("%d == %d\n", ui, si);
    printf("%ud == %ud\n", ui, si);
}

运行此命令时，您将得到以下输出，尽管这两个值都赋值为-1，且声明方式不同。

signed < 0
-1 == -1
4294967295d == 4294967295d

一般来说，这是正确的。在不知道你为什么要寻找差异的情况下，我想不出有符号和无符号之间的任何其他区别。

根据我们在课堂上学到的，有符号整数既可以表示正数也可以表示负数，而无符号整数只能表示非负数。

例如，看一个8位的数字:

无符号值为0到255

带符号的取值范围为-128 ~ 127

为了完整起见，这里只提几点:

this answer is discussing only integer representations. There may be other answers for floating point; the representation of a negative number can vary. The most common (by far - it's nearly universal today) in use today is two's complement. Other representations include one's complement (quite rare) and signed magnitude (vanishingly rare - probably only used on museum pieces) which is simply using the high bit as a sign indicator with the remain bits representing the absolute value of the number. When using two's complement, the variable can represent a larger range (by one) of negative numbers than positive numbers. This is because zero is included in the 'positive' numbers (since the sign bit is not set for zero), but not the negative numbers. This means that the absolute value of the smallest negative number cannot be represented. when using one's complement or signed magnitude you can have zero represented as either a positive or negative number (which is one of a couple of reasons these representations aren't typically used).

是的，无符号整数可以存储大的值。 不，有不同的方式来表示正数和负数。 是的，有符号整数可以包含正数和负数。

除此之外，在C语言中，你不能溢出一个无符号整数;行为被定义为模算术。您可以溢出一个有符号整数，并且在理论上(尽管在当前主流系统上没有实践)，溢出可能会触发一个错误(可能类似于除零错误)。