adding new data into text file?

[student 123]

Hi, I need help in how do we add new data into a text file. But then the file has only a limit for 20 students. If there is no space for another new student, replacing the No.1 student into the new student detail is required. For example;

In a text file
No student year
1 chris 2nd
2 hanna 1st

The question now is that, I don't know how to enter the new student detail without changing the No.1 student. And if the limit has passed, I don't know how to replace the No.1 student into a new student. Can someone help me?

So far I only managed to write in the No.1 student only into the text file.

cout << "number " << j+1 << endl;

cout << "Enter student name: " << endl;
cin >> student_name;
cout << setw(10) << fixed << student_name << endl;

cout << "Enter student level: ";
cin >> level;


cout << "\nEnter the name of the file you want to create: ";
fflush(stdin);
cin.getline (FileName,20);
ofstream Student(FileName);
{
Student << j+1 << " " << student_name << " " << level << endl;
}

[student 123]

I had tried to do 'for loop' for the entering the new student_name and level, but then, the No.1 student will eventually lost.

What I have done is this
for(j=0;j<20;j++){
cout << "number " << j+1 << endl;

cout << "Enter student name: " << endl;
cin >> student_name;
cout << setw(10) << fixed << student_name << endl;

cout << "Enter student level: ";
cin >> level;
}

Is there any other way to not the data (only apply when there is still space in the text file)?

[student 123]

Correction;
Is there any other way to not lost the data (only apply when there is still space in the text file)?

[hanst99]

I don't really understand what you are saying, and I don't really understand why you had to split it up into 3 posts, but couldn't you just put all of the students into an array before writing them to a file, and just write the last 20 of them? If the file is opened in write mode, it should overwrite all previous content so the student list having changed should be a non-issue.

[ultifinitus]

Sure there's definitely a way.... If I understand correctly you only want to put 20 students into a text file, correct?

So if, for some reason, the first time you don't output the full 20 students, you want to append the data with the rest of the students?