invalid operands to binary + (have 'struct student' and 'int')

Question

I am trying to return a structure variable from the function, i created a function getInformation to get the data but i got an error said "Invalid operands to binary + (have 'struct student' and 'int')", What does it mean? and how can i fix it?

 int main(){
 struct student *s1;
 int n;
 
printf("Enter how many data: ");
scanf("%d", &n);
 
s1 =(struct student *) malloc(n *sizeof(struct student));  

if ( s1 == NULL) 
{
    printf("memory not available");
    return 1; // exit(1); stlib.h
}

for(int i = 0; i < n; i++ ) 
{
    printf("\nEnter details of student %d\n\n", i+1);
     *s1 = getInformation();
}

}
    
struct student getInformation(struct student *s1,int i)   
{   
  struct student s;

    scanf("%d", (s+i)->age);    

    printf("Enter marks: ");
    scanf("%f", (s+i)->marks);

  return s;
}                   
    

Here is my structure

struct student {                                                    
int age;
float marks; 
};
    

Answer 1

Reason for error :scanf("%d",(s+i)->age);. Here, s is not a pointer to structure. So, adding i gives you error, because both s and i are of different types ( s is of type struct student but i is of type int).

#include <stdio.h>
#include<stdlib.h>
struct student
{
    int age;
    float marks;
};

struct student getInformation(struct student *s1);

int main()
{
    struct student *s1;
    int n;

    printf("Enter how many data: ");
    scanf("%d", &n);

    s1 = malloc(n * sizeof(struct student));

    if (s1 == NULL)
    {
        printf("memory not available");
        return 1; // exit(1); stlib.h
    }

    for (int i = 0; i < n; i++)
    {
        printf("\nEnter details of student %d\n\n", i + 1);
        *(s1+i) = getInformation(s1+i); //Changed the function call
    }

    for(int i=0;i<n;i++)
    {
        printf("%d ",s1[i].age);
        printf("%f ",s1[i].marks);

    }
}

struct student getInformation(struct student *s1)
{
    
    scanf("%d", &(s1->age));

    printf("Enter marks: ");
    scanf("%f", &(s1->marks));

    return *s1;
}

The output is :

Enter how many data: 3

Enter details of student 1

23
Enter marks: 67

Enter details of student 2

34
Enter marks: 99

Enter details of student 3

24
Enter marks: 56
23 67.000000 34 99.000000 24 56.000000