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Course.sol

pragma solidity 0.5.1;

contract Course {
    
    address admin;
    address ManagerContract;
    address instructor;
    int courseNo;
    
    struct Marks{
        int midsem;
        int endsem;
        int attendance;
    }
    
    mapping (int => Marks) student;
    mapping (int => bool) isEnrolled;
    
    constructor(int c, address inst, address adm) public {
        ManagerContract = msg.sender;
        courseNo = c;
        instructor = inst;
        admin = adm;
    }
    
    function kill() public{
        //The admin has the right to kill the contract at any time.
        //Take care that no one else is able to kill the contract
        require(
                msg.sender == admin,
                "Sender not authorized."
        );
        address payable tmpaddr = address(uint160(admin));
        selfdestruct(tmpaddr);
    }
    
    function enroll(int rollNo) public {
        //This function can only be called by the ManagerContract
        //Enroll a student in the course if not already registered
        require(
                msg.sender == ManagerContract,
                "Sender not authorized."
        );
        require(
                ! isEnrolled[rollNo],
                "Already enrolled."
        );
        student[rollNo].midsem = 0;
        student[rollNo].endsem = 0;
        student[rollNo].attendance = 0;
        isEnrolled[rollNo] = true;
    }
    
    function markAttendance(int rollNo) public{
        //Only the instructor can mark the attendance
        //Increment the attendance variable by one
        //Make sure the student is enrolled in the course
        require(
                msg.sender == instructor,
                "Sender not authorized."
        );
        require(
                 isEnrolled[rollNo],
                "Not enrolled."
        );
        student[rollNo].attendance += 1;
    }
    
    function addMidSemMarks(int rollNo, int marks) public{
        //Only the instructor can add midsem marks
        //Make sure that the student is enrolled in the course
        require(
                msg.sender == instructor,
                "Sender not authorized."
        );
        require(
                 isEnrolled[rollNo],
                "Not enrolled."
        );
        student[rollNo].midsem += marks;
    }
    
    function addEndSemMarks(int rollNo, int marks) public{
        //Only the instructor can add endsem marks
        //Make sure that the student is enrolled in the course
        require(
                msg.sender == instructor,
                "Sender not authorized."
        );
        require(
                 isEnrolled[rollNo],
                "Not enrolled."
        );
        student[rollNo].endsem += marks;

    }
    
    function getMidsemMarks(int rollNo) public view returns(int) {
        //Can only be called by the ManagerContract
        //return the midSem, endSem and attendance of the student
        //Make sure to check the student is enrolled
        
        require(
                msg.sender == ManagerContract,
                "Sender not authorized."
        );
        
        require(
                isEnrolled[rollNo],
                "Not enrolled."
        );
        
        return (student[rollNo].midsem);
        
    }
    
    
    function getEndsemMarks(int rollNo) public view returns(int) {
        //Can only be called by the ManagerContract
        //return the midSem, endSem and attendance of the student
        //Make sure to check the student is enrolled
        require(
                msg.sender == ManagerContract,
                "Sender not authorized."
        );
        
        require(
                isEnrolled[rollNo],
                "Not enrolled."
        );
        
        return (student[rollNo].endsem);
    }
    
    
    function getAttendance(int rollNo) public view returns(int) {
        //Can only be called by the ManagerContract
        //return the midSem, endSem and attendance of the student
        //Make sure to check the student is enrolled
        require(
                msg.sender == ManagerContract,
                "Sender not authorized."
        );
        
        require(
                isEnrolled[rollNo],
                "Not enrolled."
        );
        
        return (student[rollNo].attendance);
    }
    
    function isEnroll(int rollNo) public view returns(bool){
        //Returns if a roll no. is enrolled in a particular course or not
        //Can be accessed by anyone
        return (isEnrolled[rollNo]);
    }
    
}

Manager.sol

pragma solidity 0.5.1;
import "./Course.sol" ;

contract Manager {
    //Address of the school administrator
    address admin;
    
    mapping (address => int) student;
    mapping (address => bool) isStudent;
    mapping (int => bool) isCourse;
    mapping (int => Course) course;
    
    int rollCount = 19111000;
    
    //Constructor
    constructor() public{
        admin = msg.sender;
    }
    
    
    function kill() public{
        //The admin has the right to kill the contract at any time.
        //Take care that no one else is able to kill the contract
        require(
                msg.sender == admin,
                "Sender not authorized."
        );
        address payable tmpaddr1 = address(uint160(admin));
        selfdestruct(tmpaddr1);
        
    }
    
    function addStudent() public{
        //Anyone on the network can become a student if not one already
        //Remember to assign the new student a unique roll number
        require (
                !isStudent[msg.sender],
                "Already a student."
            );
        student[msg.sender] = rollCount;
        rollCount += 1;

    }
    
    function addCourse(int courseNo, address instructor) public{
	//Add a new course with course number as courseNo, and instructor at address instructor
    //Note that only the admin can add a new course. Also, don't create a new course if course already exists

        require(
                msg.sender == admin,
                "Sender not authorized."
            );
        require(
                !isCourse[courseNo],
                "Course already exist."
            );
        
        course[courseNo] = new Course(courseNo,instructor, admin);
    }
    
    function regCourse(int courseNo) public{
        //Register the student in the course if he is a student on roll and the courseNo is valid
        require(
                isStudent[msg.sender],
                "Not a valid student."
            );
        require(
                isCourse[courseNo],
                "Not a valid course."
            );
        // Register
        course[courseNo].enroll(student[msg.sender]);

    }
    
    function getMyMarks(int courseNo) public view returns(int, int, int) {
        //Check the courseNo for validity
        //Should only work for valid students of that course
	    //Returns a tuple (midsem, endsem, attendance)
        require(
                isCourse[courseNo],
                "Not a valid course."
            );
        require(
                course[courseNo].isEnroll(student[msg.sender]),
                "Not an enrolled student."
            );
        
        
        int ms = course[courseNo].getMidsemMarks(student[msg.sender]);
        int es = course[courseNo].getEndsemMarks(student[msg.sender]);
        int at = course[courseNo].getAttendance(student[msg.sender]);
        
        return (ms, es, at);
        
    }
    
    function getMyRollNo() public view returns(int) {
        //Utility function to help a student if he/she forgets the roll number
        //Should only work for valid students
	    //Returns roll number as int
	    require(
                isStudent[msg.sender],
                "Not a valid student."
            );
        return (student[msg.sender]);

    }
    
}