c - 结构员工 {} 比较结构 {} 员工

Question

我读了一个教程，其中有这个结构:

struct
{
    char Name[25];
    int Age;
    float SkillRating;
} Employee;

defines a new aggregate, called Employee, containing fields called Name (of type character), Age (of type integer), and SkillRating (of type float).

相比之下，C 语句:

struct EmployeeType
{
    char Name[25];
    int Age;
    float SkillRating; 
};

does not define a new aggregate variable, but defines a new aggregate type, EmployeeType. This new data type could then be used to declare variables in the same way as a primitive data type. That is, in the same way that C allows the variable x to be declared as an integer using the statement

我在这里很困惑。 'Emplyee`放在不同的位置有区别吗？

我猜他们是一样的。

Answer 1

在第一种情况下，struct 是未命名的，Employee 是该未命名结构的变量。可以直接这样修改:

int main()
{
    Employee.Age = 100;
    return 0;
}

在第二种情况下，EmployeeType 只是一个类型，但您还没有创建它的任何实例。您可以创建任意数量的实例:

int main()
{
    struct EmployeeType a;  // employee on the stack
    a.Age = 100;
    struct EmployeeType *b = malloc(sizeof(struct EmployeeType)); // employee on the heap
    if (b) { // set the age of b if the allocation succeeded
        b->Age = 100;
    }
    free(b); // malloc-allocated memory must be freed afterwards 
    return 0;
}

你甚至可以同时做这两件事:

struct EmployeeType
{
    char Name[25];
    int
        Age;
    float SkillRating;
} Employee;

在这里，Employee 是它的一个实例，但您可以创建其他实例:

int main()
{
    Employee.Age = 100;
    struct EmployeeType a;  // employee on the stack
    a.Age = 100;
    return 0;
}