%08x

x 表示 16 进制

08 表示显示出 8 个字符

int main() {
	unsigned int a = 0xfffffff7;
	unsigned char i = (unsigned char) a;

	char *b = (char *)&a;

	printf("%x, %x
", i, *b);
	printf("%08x, %08x
", i, *b);
	
	return 0;
}

f7, fffffff7
000000f7, fffffff7