打印C中字符变量的整数值(Printing Integer value of character variable in C)

打印C中字符变量的整数值(Printing Integer value of character variable in C)

最近在我的研究所，我得到了一个代码，并被要求找出答案。 代码看起来像这样。

#include <stdio.h> int main() { char ch=500; printf("%d\n",ch); }

输出将为-12

我的问题是：我如何计算这种代码的值？ 是否有任何寻找价值的公式或流程？

Recently in my Institute I was given a code and was asked to find out the answer. The code looks like this.

#include <stdio.h> int main() { char ch=500; printf("%d\n",ch); }

The output will come as -12

My question is: How can I calculate the value for this kind of code? Is there any formula or process for finding the values?

最满意答案

代码在语法上是正确的，但没有按照你的想法做。 正如Paul Hankin建议你的编译器应该给你一个警告，因为你试图设置一个不适合char变量中的char的数字。

char是1个字节，因此如果有符号则可以存储最多127个数字，如果未签名则可以存储255个数字。 该值溢出，仅考虑低8位。

500 = 0b111110100

仅取低8位：0b11110100

MSB为1，因此它为负数。

1补码加1是0b00001100，即12

这就是你得到-12的原因。

用short或int替换它应该正确打印500。

The code is syntactically correct but not doing what you think. As Paul Hankin is suggesting your compiler should give you a warning as you are trying to set a number that does not fit into a char in a char variable.

A char is 1 byte so it can store a number up to 127 if signed or 255 if unsigned. The value overflows and only the lower 8 bits are taken into account.

500 = 0b111110100

Take only the lower 8 bits: 0b11110100

The MSB is 1 so it's negative number.

1-complement plus 1 is 0b00001100 which is 12

That's why you get -12.

Replacing it by a short or an int should correctly print 500.