C 代码中的结构和指针

Question

What asterisk ' * ' doing in int function before data variable?What is the aim of putting pointer of type struct weather in brackets?Also why before rain is ' --> 'sign?How it works in this code? Thank you in advance!

typedef struct
{
    int rain;
    double temp;
    double wind;
} weather;

int rainTot(weather* data)
{
    int i, total = 0;
    for (i = 0; i < 12; i++)
    {
        total += (data + i)->rain;
    }
    return total;
}

btw code for main

int main()
{
    setvbuf(stdout, NULL, _IONBF, 0);
    int i = 0;
    weather *values = (weather*)malloc(12 * sizeof(weather));

    FILE *data;
    data = fopen("astana.txt", "r");
    if (data == NULL)
    {
        printf("Problem opening files.");
        return 1;
    }

    do
    {
        fscanf(data, "%i %lf %lf", &(values + i)->rain, &(values + i)->temp, &(values + i)->wind);
        i++;
    }
    while (!feof(data));

    printf("The total rainfall for one year is: %i\n", rainTot(values));
    printf("The lowest average temperature is: %g\n", tempAvgMin(values));
    printf("The average of wind speed for one year is %.2g\n\n", windAvg(values));
    print(values);

    free(values);
    fclose(data);

    return 0;
}

Answer 1

Asterisk * means this variable is a pointer.

Pointer in paramaters usually has two reason : 1. You nead modify paramaters in sub-function 2. Paramaters are to many,so transfer paramters' address(pointer) to function to simplify。