c - 为什么当变量不相等时语句为真，而当变量相等时语句为假？

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已关闭。这个问题是 not reproducible or was caused by typos 。目前不接受答案。

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这个问题是由拼写错误或无法再重现的问题引起的。虽然类似的问题可能是 on-topic在这里，这个问题的解决方式不太可能帮助 future 的读者。

已关闭 3 年前。

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我昨天刚开始学习 C，遇到了一个问题，但我不明白为什么会发生。

代码是这样的

#include<stdio.h>
int a=0;
void main() {
    if (a=13) {
        printf("Number Is Equal\n");
    }
    else {
        printf("Not Equal\n");
    }
}

它应该显示不等于，但它仍然显示数字相等，我也尝试了其他数字来代替 int a；如果我分配 int a=13 的值，然后如果我运行语句 if(a=13) 那么它是真的，但是如果我在两个地方都对 0 执行相同的操作，那么它显示不相等。

Answer 1

您使用赋值运算符 = 将 13 赋给 a。使用 == 进行比较。

示例:

int a=0;
void main()
{
    // Here, a is being checked to see if it is equal to the int 13.
    // a=13 would be assigning 13 to a, and then checking to see if
    // a is "truthy", or, not 0, which is why it was true for you every time.
    if (a == 13) {
        printf("Number Is Equal\n");
    }else{
        printf("Not Equal\n");
    }
}

NOTE: The C Standard specifies that main() will return type int, (e.g. int main(){return 0;}) when in a hosted environment. You can deviate from this when you're in a freestanding environment, at which point this becomes implementation defined. It is not likely that you are using a freestanding environment. The odds are that you are in a hosted environment where your use of type void for main would violate the C Standard.