Cannot print char array

Try this approach:

enum Grade{
    A,
    B,
    C,
};

const char * GetGradeStr(Grade grade){
    switch(grade){
    case A:return "First";
    case B:return "Second";
    case C:return "Third";
    }
}

char sname[10];
Grade grade;

...
    grade = A;

...
    cout<<sname<<"'s total grade ranks: "<<GetGradeStr(grade);

This makes grade into an enum, which means only the 3 values are valid values, and then returns the correct string as a "String Literal"

Maybe I can add something, to make things even clearer for you. You need to understand the difference between char arrays and pointers. A pointer is just a variable which points to some area in memory. You can malloc memory and store the address into a char* - this will behave similar to a char array. But it's not the same.

A char array (and any array in C/C++) has to have a known size at compile time. The compiler will then "allocate" this memory statically, as opposed to allocating at runtime via malloc or new. This array can now be implicitly converted to a char* - this is what happens when you print it, for example. Look at the following code:

char* foo = "Hello world";

What this actually does is something like this:

// Compiler generated "global constant",
// somewhere in your executable
const char fooString[] = "Hello world";

char* foo = fooString;

For every string literal you use in your code, the compiler will generate such a "global constant". By assigning to a char pointer, the pointer now points to that constant's memory address, therefore it's possible to print it, index it (foo[2]), copy it, etc.

If you're using char arrays, the compiler will also allocate space at compile time. The char sname[10] for example will cause every object of class abc to contain memory for 10 chars (in addition to the other members etc.) Now when you reference sname in your code, it's type will be char[10], but it can be (implicitly) converted to achar*` pointing to the first char in the array. Now let's have a look at the following code:

grade = "First";
grade = "Second";
grade = "Third";

If we remember that string literals are converted to global constants, it actually is something like the following:

const char[] str1 = "First";
const char[] str2 = "Second";
const char[] str3 = "Third";

grade = str1;
grade = str2;
grade = str3;

As you might guess now, this will work nicely if grade is a char pointer: It will just point to one of the constant string literals, and can then be used to print it etc. But if grade is an array, the compiler sees an assignment from char* to char[] - which is not possible. But it is possible using strcpy - why? Because strcpy takes to char pointers as arguments. Thus, the compiler will implicitly convert the char array grade into a pointer to it's first element, and pass this to strcpy.

You have defined grade to be a char and not a char * . Please update that to become char * then you can assign those values like 'First' etc

Edit

#include <iostream.h>
#include <conio.h>

class abc
{
    private:
            int rno,m1,m2,tot;
            char sname[10];
            char * grade;
    public:
            void getinput()
            {
                cout<<"Enter roll no:"<<endl;
                cin>>rno;
                cout<<"\nEnter mark 1:"<<endl;
                cin>>m1;
                cout<<"\nEnter mark 2:"<<endl;
                cin>>m2;
                cout<<"\nEnter student name:"<<endl;
                cin>>sname;
                cout<<endl;
                // Getting the returns.
                //tot = gettotal();
                //grade = getgrade();
            }

            void gettotal()
            {
                tot = m1+m2;
                // Returning the total to getinput's "tot" part.
                //return (tot);
            }

            void getgrade()
            {
                if(tot >= 150)
                {
                    grade = "First";
                }
                else if(tot >= 100)
                {
                    grade = "Second";
                }
                else
                {
                    grade = "Third";
                }
                // Returning the total to getinput's "grade" part.
                //return (grade);
            }

            void display()
            {
                cout<<sname<<"'s total grade ranks: "<<grade;
            }
 };


 int main()
 {
    abc a;
    a.getinput();
    a.gettotal();
    a.getgrade();
    a.display();
 }