Some c++ Important Questions

Q.what is token?

Ans:- It is basically smallest unit of programs .It is main building block of any programming language.

Various types of tokens used in c++ are : -
a. Keywords
b. Identifiers
c. Literals
d. Punctuators
e. Operators

Q.what is identifiers?

Ans- All the words used in c/c++ program i.e.names of variables,functions,labels,and various other user defined objects except the keywords are called identifiers.

Rules for identifiers:-

1. It should not be any keywords/

2. The first character must be a letter or an underscore, and subsequent characters must be either letter,digits or underscore.

3. The identifiers should not have the same name as functions that are in c/c++ library.

Here are some correct and incorrect identifiers-

Correct            Incorrect

Count                  1count
Test23                hi!there
High_balance            high….balance, high balance   
   

Q.difference between function signature and function prototype?

Ans.
* Function signature -

• The function name along with their arguments list and their data types is known as function signature.
•  It is a part of function prototype that the compiler uses to perform overloaded resolution (i.e function overloading )

*Function Prototype -

• The function prototype is even known as function declaration.
• The function prototype contains function name ,return type ,all argument list and their data types and ended by a semicolon.

Void function(int,char,double,float) ;


The highlitted syntax is function signature.
While the whole syntax is function prototype or declaration.

Q.Difference between actual and formal argument?

Ans.

-> When we pass the arguments at the time of invoking(calling) the function,then the argument is known as actual argument.

->The arguments declared inside the function definition is known as formal arguments.

Consider a Example-

#include<iostream>
Using namespace std;

Void add(int x,int y)
{
    Cout<<x+y<<endl;
}

Int main()
{
    int i=5,j=6;

    add(i,j);

    Return 0;
}

In the above example i and j is the actual argument.
And x and y is formal arguments.

->When we call by value-The value of the actual arguments is passed and copied  to the  formal arguments.

->When we call by reference or address- The address of the actual argument is copied to the formal arguments.

Q. Different access modifiers in c++?
Ans.
C++ supports 3 access modifiers.
1.private
2.protected
3.public

1.Private:-

• The members declared inside the private0 access modifiers can not be accessed directly by the object of a class.
• The private member or functions can be used only by the object of class through   public member function of class.
• The private member can not be inherited in any way.
• defaultly the members declared inside the class is private.

2. Protected:-

• The members declared inside the protected access modifiers can not be accessed directly by the object of a class.
• The protected member or functions can be used only by the object of class through   public member function of class.
• The private member can be inherited.(only this features makes it different from private access modifiers).

3.Public :-

• The public member can be accessed outside the class directly by the object of a class.
• It is the lowest level of security.