passing

[ulti-killer]

typedef struct{
        int ID;
        char name[50];
        double hor_total;
    }group;
    group salesman[SIZE];

int nextid();


int nextid(int last, int resetId)
{
    if ( resetId == 0)    
    {
        static int last;
        return ++last;
    }

    else
    {
        static int last = 0;
        return ++last;
    }

    
}
int main()
{
    FILE *readId;
    int a, b, c = 0, last; 
    double ver_total = 0, max = 0; 
    int id, lastId, resetId = 0;


    if ( (readId = fopen("nextid.txt","r")) == NULL)
        printf("Cannot open nextid.txt file");
    else
    {
        fscanf(readId,"%d",&lastId);
        nextid(lastId, resetId);
    }
        for(a=0; a<SIZE; a++)
        {
            salesman[a].ID = nextid();
            salesman[a].hor_total = 0;
        }
}

I cannot use salesman[a].ID = nextid(); anymore. So, how can I past last variable in nextid() to salesman[a].ID?

[laserlight]

Eh, your nextid function really confused me because at a glance, it looked like you were incrementing the same variable named last regardless of the value of resetId, but actually the variable named last in the else branch is a different variable. Personally, I think it would be clearer to write:

int nextid(int currentId, int isReset)
{
    static int lastId = 0;
    if (isReset)
    {
        last = currentId;
    }
    return ++lastId;
}

I cannot use salesman[a].ID = nextid(); anymore. So, how can I past last variable in nextid() to salesman[a].ID?

That sounds trivial, e.g.,

salesman[a].ID = nextid(lastId, resetId);

Actually, this is horrible: you have a variable named readId that is not an id: it is a file pointer. Then you have a variable named lastId that is an id. Then you have another variable named resetId that is not an id: it is a flag variable. Oh, and in your nextid function and redundantly in your main function, you have a variable named last that is an id variable. Seriously, if you want to name your id variables with a fooId pattern, well and good, but don't go about naming non-id variables in the fooId pattern too, and don't name id variables with some other pattern unless you have very good reason to do so.

[ulti-killer]

What is fooId pattern?

[laserlight]

What is fooId pattern?

Your naming pattern whereby you have a name followed by an "Id" suffix.

[Click_here]

I know that as "Smurf Naming Convention" from Coding Horror: New Programming Jargon