Basics of C++ Language : MCQs & PYQs with Explanation

Option B

In C++, cout is an predefine object of the output stream class (ostream) defined in the header file iostream.

• It is used to display output on the console.
• The cout works with the insertion (put to) operator << to print data.

#include<iostream>
using namespace std;
int main() 
{
    cout<<"Suraku Academy";
    return 0;
}

Option B

The cout is a predefined object in C++ from the iostream library used for console output. Generally the name cout is breaks down as, "c" for character (handles character streams) and "out" for output. It works with the insertion or put to operator << to print data.

Option B

In C++, an alias means another name for an already existing variable. This is done using a reference variable.

• A reference variable refers to the same memory location as the original variable.
• Reference variable is an internal pointer.
• Declaration of reference variable is preceded with ‘&’ symbol.
• Reference variable must be initialized at the time of declaration.
• It can be initialized with already declared variable only.
• Reference variables cannot be updated.
• Any change made through the reference affects the original variable.

Syntax:
             Data_type &Reference_Name= Referent;

Option D

In C++, every statement must end with a semicolon. If a programmer forgets to write a semicolon, the compiler shows an error, but it does not display the messages given in the options. 
Different C++ compilers show different error messages, such as “expected ‘;’ before …” or “missing ‘;’,” but none of these matches exactly with “Semicolon Missing,” “Statement Missing,” or “Error in Statements.”

Option C

In C++, a header file contains declarations such as functions, classes, constants, and macros. These files are included in a program using the #include directive. There are two types of header files, predefine header files iostream.h, conio.h and user-defined header files created by the programmer.
User-defined header files in C++ typically use the extension “.h”. For example, #include "myheaderfile.h"

Option C

C++ is an object-oriented programming language. It was developed by Bjarne Stroustrup at AT&T bell laboratories in the Murray Hill, New Jersey, USA in the year 1979. It is an extension to C with number of new features added.
The starting name of C++ was “C with Classes” and in 1983 the name is changed to C++.
The first use of class construct in a programming language occurred in 1962 in the language Simula67.

Option B

In C++, all preprocessor directives always start with the hash symbol (#). Preprocessor directives are processed before compilation. They are used for tasks like file inclusion, macro definition, and conditional compilation.
E.g.:
#include <iostream>
#define PI 3.14

Option B

In C++, a Namespace is used to organize identifiers such as variables, functions, classes, and objects. It provides a separate scope to avoid naming conflicts in large programs.
When two identifiers have the same name, namespaces help distinguish them by placing them in different scopes.
#include<iostream>
using namespace std;
namespace A
{
    int value = 10;
}
namespace B
{
    int value = 20;
}
int main()
{
    cout<<A::value<<endl;
    cout<<B::value;
    return 0;
}
The A::value and B::value belong to different namespaces. The namespace defines the scope of these identifiers.

Option C

In the traditional Turbo C++ environment, two different shortcut keys are used:

• Alt + F9 for compiles the program.
• Ctrl + F9 for runs the program. It automatically compiles (if needed) and then runs the program.

Option C

The void keyword in C++ is used to represent the absence of a data type or value. It tells the compiler that no value is associated in a particular situation. The void keyword is mainly used in functions, pointers, and parameter lists.
One common use of void is as a function return type. When a function performs some tasks but does not return any value, its return type is declared as void.
For example, in the function declaration void display();, the keyword void indicates that the display() function does not return any value.
The void keyword is also used to indicate that a function does not accept any arguments.
For example, in the function declaration void display(void);, the keyword void inside the parentheses indicates that the display() function does not accept any arguments.
Another important use of void is with pointers. A void pointer can store the address of any data type.
For example, in the declaration void *ptr;, the pointer ptr can point to an int, float, char, or any other data type.

Thus, the void keyword is very important in C++ because it specifies “no value”, “no argument”, or “generic type” depending on its usage.

Option C

In C++, new and malloc are both used for dynamic memory allocation, but they behave differently:
The new is an operator, while malloc is a function. This means new is handled by the compiler, whereas malloc is a library function from C. The statement (I) is true.
The new invokes the constructor for object initialization, while malloc only allocates raw memory and does not call any constructor. The statement (II) is true.
The malloc returns a void pointer, so it often needs typecasting in C++, whereas new automatically returns a pointer of the required type. The statement (III) is true.

Option B

In C++, the bool data type is used to store Boolean values. A Boolean variable can hold only two possible values either true or false.

• bool status=true;
• bool result=false;

These values are mainly used in conditional statements, decision making, and logical operations.
Thus, the bool data type can store only two values.

Option B

In C++, cin and cout are not functions. They are objects created by the C++ standard library. The cin is a predefined object of the class istream (input stream) while the cout is a predefined object of the class ostream (output stream). Both are declared in the <iostream> header file and belong to the std namespace.

Option A

In C++, the operator << is known as the insertion operator when used with output streams. It is used to insert data into an output stream, such as cout and sends (inserts) data from the program to the output device (screen).

• Extraction operator is >> and used with cin.

Option C

C++ uses the bottom-up approach, which is a core philosophy of object-oriented programming. In this approach, programs are built by first creating small, reusable components such as classes and objects, and then combining them to form larger and more complex systems.