As it was already said you have to use break
for any case label.
switch (coursepick)
{
case 1: course= "Maths"; break;
case 2: course= "Quantum"; break;
case 3: course= "Reality"; break;
default: break;
}
But in any case the code is invalid bacause if the user will enter a number outside the acceptable range variable course will not be assigned. However you will use this unassigned variable in statement
phys[0]->addCourse(course,mark);
Also it is not clear why the variable is defined outside the loop.
I would write the loop the following way
enum { Maths = 1, Quantum, Reality };
for ( int p = 0; p < 3; p++ )
{
do
{
cout << "\nPlease select a course:" <<endl;
cout<<"1. Maths\n";
cout<<"2. Quantum\n";
cout<<"3. Reality\n";
cin >> coursepick;
if ( !( Maths <= coursepick && coursepick <= Reality ) )
{
cout << "Error. Invalid input. Please repeat" << std::endl;
}
} while ( !( Maths <= coursepick && coursepick <= Reality ) );
switch (coursepick)
{
case Maths: course= "Maths"; break;
case Quantum: course= "Quantum"; break;
case Reality: course= "Reality"; break;
default: abort();
}
cout << "Please insert the course mark:" << endl;
cin >> mark;
cin.ignore();
phys[0]->addCourse( course, mark );
}