Why showing error

Question

https://code.sololearn.com/cpzhNHE6hS0A/?ref=app

Answer 1

Don't use typedef union, just use : union id in the first line
This :
union id{
int id_num;
char name[20];
}id;

Answer 2

Typedef doesn't work the way you think it does, eg.
Typedef struct {
// Some data
} ID;
now ID will be the structure, and then it will work like this :
ID Ob;
// An object of the structure

Eg.2

typedef double Dec;
Now you can use Dec as a keyword in place of double
Now I will modify your code according to that, and it becomes :

#include <stdio.h>
#include <string.h>

typedef union{
int id_num;
char name[20];
}id;

void set_id (id *item);
void show_id (id item);

int main() {
id item;

set_id(&item);
show_id(item);

return 0;
}

void set_id(id *item) {
item->id_num = 42;
}

void show_id(id item) {
printf("ID is %d", item.id_num);
}

Answer 3

Why