Question

C语言的一个问题。

Assume a programmer wrote the following variable declarations. The initial values have been omitted (. . . ), but you are provided with the representations of the variable values in memory. unsigned char uc = ...; // 00001100 in memory signed char sc = ...; // 11111011 in memory What initial values did the programmer specify with variables uc and sc? • Hint: For a signed variable, the representation of the variable’s value in memory will be in two’s complement. For an unsigned variable, the representation will be binary.

Answer 1

简单来卜脊说，题目问的是：
uc是unsigned char，内存中二进制表示是00001100。
sc是signed char，内存中二进制表示的是11111011。
求uc，sc的初值。

unsigned char是无符号的，00001100就是十进制中的12。
signed char是有符号的，在内存中以补码形式存在，
11111011首位是1，因此是负数，
按位取反，末尾加1得到：00000101是型春渗十进森坦制的5，
因此是-5.

所以：
unsigned char uc=12;
signed char sc=-5;