You often put semicolon after class or function definition, while in the next line you are providing the body of the class or the function. In those cases you mustn't add a semicolon.
- class Section;
- getN(char N, double RN);
You should initialise your class with a constructor. The constructor has the same name as the class and it can receive parameters to set up initial values. It doesn't have a return value (as it is always the class itself)
Section(char * name, double roll) :
Functions that belong to a specific class must be declared within that class. Your functions EnterName and EnterRN are declared (and defined) outside of the scope of your Selection class.
To store a "text", you have to use a string. You can either use a C language type string (C-String), which is a character array: char *; or you can use a C++ string: std::string. I'd recommend using the latter since you're writing C++ code, so why not use the language features? The type char is meant to store a single character only not a sequence of them (text).
A Better Solution
I rewrote the whole code as it had quite a numerous problems (both syntax and both design problems).
Note: I'm not entirely sure what your class and your code wants to do, so feel free to change it. :)
// Constructor to initialise the class
Section(std::string name, double roll) :
const std::string & GetName() const // the const means this function would not change the class, remove const if you want your function to change the state of the class
double GetRoll() const // the const means this function would not change the class, remove const if you want your function to change the state of the class
std::cout << "Enter the name of the student: ";
std::cin >> name;
std::cout << "Enter the roll: ";
std::cin >> roll;
Section section(name, roll);
std::cout << "Section: " << section.GetName() << ", " << section.GetRoll() << std::endl;