C++

C++ extends C with object-oriented features, stronger type checks, and libraries for data structures, algorithms, and more. It is used in software ranging from operating systems to games. Programs are saved with a .cpp extension and compiled with compilers like g++. Clear structure in C++ means organizing code into functions and classes with readable naming. This chapter introduces basics such as output with cout, variables, conditions, loops, functions, and ends with a subtraction calculator as the final example.

Hello world

The first program includes iostream for input and output and uses cout.

#include <iostream>
using namespace std;

int main() {
  cout << "Hello, world!" << endl;
  return 0;
}

Variables and types

C++ supports types such as int, double, char, and string. Use descriptive names to improve clarity.

int age = 15;
double weight = 52.3;
char grade = 'B';
string name = "Alice";

Conditions

C++ conditions use if, else, and switch. Braces { } group instructions clearly.

int score = 85;
if (score >= 50) {
  cout << "Pass" << endl;
} else {
  cout << "Fail" << endl;
}

Loops

Loops in C++ repeat tasks: for for counters, while for conditions. Keep logic short for clarity.

for (int i = 1; i <= 3; i++) {
  cout << "Count " << i << endl;
}

Functions

Functions help organize reusable logic. A return type must always be declared in C++.

int multiply(int x, int y) {
  return x * y;
}

Final example — calculator for subtraction

The following C++ program reads two numbers, subtracts them, and prints the difference. Save as main.cpp and compile with g++ main.cpp -o main.

main.cpp

#include <iostream>
using namespace std;

int main() {
  double minuend, subtrahend, difference;
  cout << "Enter minuend: ";
  cin >> minuend;
  cout << "Enter subtrahend: ";
  cin >> subtrahend;
  difference = minuend - subtrahend;
  cout << "Difference: " << difference << endl;
  return 0;
}

MCQs

1. Which header file is required for input and output in C++?

(a) stdio.h

(b) iostream

(d) string.h

► (b) iostream

2. What is the correct file extension for a C++ source file?

(a) .c

(b) .cpp

(d) .cp

► (b) .cpp

3. Which operator is used with cout to send data to the output stream?

(a) >>

(b) <<

(d) :=

► (b) <<

4. Which C++ statement declares a variable that stores a decimal number?

(a) int x;

(b) float x;

(d) Both (b) and (c)

► (d) Both (b) and (c)

5. Which statement is true about C++ strings?

(a) They are arrays of characters ending with '\0'

(b) They can be used with the string class in <string>

(d) None of the above

► (c) Both (a) and (b) are correct

6. What will the condition (7 < 3) evaluate to in C++?

(a) true

(b) false

(d) 0

► (d) 0

7. Which loop in C++ is guaranteed to execute at least once?

(a) for

(b) while

(d) foreach

► (c) do...while

8. Which operator is used for equality comparison in C++?

(a) =

(b) ==

(d) :=

► (b) ==

9. Which is a valid C++ function definition?

(a) int add(x, y) { return x + y }

(b) int add(int x, int y) { return x + y; }

(d) def add(x, y): return x + y

► (b) int add(int x, int y) { return x + y; }

10. Which statement about C++ arrays is correct?

(a) Array indexes start at 1

(b) Array indexes start at 0

(d) Arrays can only store characters

► (b) Array indexes start at 0

11. What is the correct syntax for including a standard header in C++?

(a) #include <filename>

(b) include "filename"

(d) #header filename

► (a) #include <filename>

12. Which keyword allows using names from the std namespace directly?

(a) using namespace std;

(b) include std;

(d) namespace std();

► (a) using namespace std;

13. Which operator is used to access members of a class or struct through an object?

(a) .

(b) ->

(d) *

► (a) .

14. Which operator is used to access members through a pointer to an object?

(a) .

(b) ->

(d) ::

► (b) ->

15. Which keyword stops a loop and transfers control after it?

(a) stop

(b) break

(d) continue

► (b) break

16. Which C++ operator creates a new object dynamically?

(a) malloc

(b) allocate

(d) create

► (c) new

17. Which keyword is used to define a class in C++?

(a) object

(b) class

(d) structclass

► (b) class

18. In the subtraction calculator, which variables store the inputs?

(a) x and y

(b) first and second

(d) num1 and num2

► (c) minuend and subtrahend