uint private latestEnrollmentNumber;

constructor() {

owner = msg.sender;

}

function addNewStudent(string calldata newStudentName,

string calldata newStudentDob, string calldata

newStudentGrade) public returns(uint){

if (msg.sender != owner) {

return 0;

}

uint newEnrollmentNumber = ++latestEnrollmentNumber;

StudentDetails newStudent = new

StudentDetails(newStudentName, newStudentDob,

newStudentGrade, newEnrollmentNumber);

students.push(newStudent);

return newEnrollmentNumber;

}

function retrieveGrade(uint studentEnrollmentNumber)

public view returns(string memory){

for (uint i=0; i < students.length; i++) {

if (students[i].getEnrollmentNumber() ==

studentEnrollmentNumber) {

return students[i].getGrade();

}

}

}

}

2.5.25 Ethereum Tokens and ERC Standards

Ethereum tokens are simply digital assets that can be represented

and traded on the Ethereum blockchain. The advantage of such

tokens is that they can be built really quickly from scratch and

deployed on Ethereum in almost no time. Also, Ethereum being a

public network, there is no extra infrastructure work that is needed.