Need assistance with Menu Driven Programming Assessment!

I am writing a program which takes in marks and manipulates the marks according to the menu selection.
I am new to programming and need a push in the right direction! My current issue isn't much that my program may be incorrect (syntax wise) its that nothing is being displayed for CASES 1.
THANK YOU!

Code:

#include <iostream>
#include <string>
#include <iomanip>
#include <cstring>
using namespace std;


int AddStudM (int Studm[], int MaxM=1000);
// prototypes above.

int main ()
{
    int loop=1;
    int choice;
    
    
    while (loop==1)
    {
          system ("CLS");                  //Question 3
          cout << " ** MENU **\n\n"
               << "0. Exit \n"
               << "1. Add Student mark \n"
               << "2. List all student marks \n"
               << "3. Calculate the marks average \n"
               << "4. Calculate the standard deviation \n"
               << "5. Delete a student mark \n"
               << "6. find the number of students via mark \n"
               << "7. Display distinct marks and their occurrences \n";
          cout << "\n\nSelect from the menu above: ";     
          cin >> choice;
          switch(choice)
          {
               case 0:
                    cout << "Good bye\n\n";
                    system ("pause");
                    exit(0);
               case 1:
                    system ("CLS");
                    int AddStudM (int Studm[], int MaxM);
                    system ("pause");
                    system ("CLS");
                    main();
                    break;
    
               case 2:
                    system("CLS");
                    cout << "\t-- List all student marks --\n\n";
                    system ("pause");
                    system("CLS");
                    break;
                    
               case 3:
                    system("CLS");
                    cout << "\t-- Calculate the marks average --\n\n";
                    system ("pause");
                    system("CLS");
                    break;
                    
               case 4:
                    system("CLS");
                    cout << "\t-- Calculate the standard deviation --\n\n";
                    system ("pause");
                    break;
                    
               case 5:
                    system("CLS");
                    cout << "\t-- Delete a student's mark --\n\n";
                    system ("pause");
                    system("CLS");
                    break;
                    
               case 6:
                    system("CLS");
                    cout << "\t-- Find the number of students via a mark --\n\n";
                    system ("pause");
                    system("CLS");
                    break;
                    
               case 7:
                    system("CLS");
                    cout << "\t-- Display distinct marks and thei occurrences --\n\n";
                    system ("pause");
                    system("CLS");
                    break;
                    
          }
          }
          
    }
    
//  1. Add a student mark!    
    
int AddStudM (int Studm[], int MaxM)


            int Mark;
            int i;
            for (i=0; i< MaxM; i++)
            {
                cout << "enter mark for student: ";
                cin >> Mark;
                Studm[i]=Mark;
            } 
    i++;
    return 0;
    }
}

If it has any value to your attempt in compiling this code, I am using Dev C++ 4.9.9.2

Well first you need to declare an array of students at the beginning of main.

Then you need to pass that array to the function in a function call (all you have is another prototype).

Finally, NEVER call main() recursively. The code will loop quite happily as written.
Eg.

Code:

               case 1:
                    system ("CLS");
                    AddStudM (Studm, MaxM);
                    system ("pause");
                    system ("CLS");
// NEVER                    main();
                    break;

At some point, you should remove all your system("foo") calls as well. There's usually a much better way to achieve the same thing.