OOPS: NOTES

1.OPERATORS IN C++

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An operator is a symbol that operates on a value to perform specific mathematical or logical computations. They form the foundation of any programming language. In C++, we have built-in operators to provide the required functionality.

An operator operates the operands. For example, 

int c = a + b;

Here, ‘+’ is the addition operator. ‘a’ and ‘b’ are the operands that are being ‘added’.

Operators in C++ can be classified into 6 types:

1. Arithmetic Operators
2. Relational Operators
3. Logical Operators
4. Bitwise Operators
5. Assignment Operators
6. Ternary or Conditional Operators

 

1) Arithmetic Operators

These operators are used to perform arithmetic or mathematical operations on the operands. For example, ‘+’ is used for addition, ‘-‘ is used for subtraction ‘*’ is used for multiplication, etc. 

Arithmetic Operators can be classified into 2 Types:

A) Unary Operators: These operators operate or work with a single operand. For example: Increment(++) and Decrement(–) Operators.

Name	Symbol	Description	Example
Increment Operator	++	Increases the integer value of the variable by one	int a = 5; a++; // returns 6
Decrement Operator	—	Decreases the integer value of the variable by one	int a = 5; a–; // returns 4

Example:

• C++

// CPP Program to demonstrate the increment // and decrement operators #include <iostream> using namespace std;   int main() {     int a = 10;     cout << "a++ is " << a++ << endl;     cout << "++a is " << ++a << endl;       int b = 15;     cout << "b-- is " << b-- << endl;     cout << "--b is " << --b << endl;         return 0; }

Output

a++ is 10
++a is 12
b-- is 15
--b is 13

Time Complexity: O(1)
Auxiliary Space : O(1)

Note: ++a and a++, both are increment operators, however, both are slightly different.

In ++a, the value of the variable is incremented first and then It is used in the program. In a++, the value of the variable is assigned first and then It is incremented. Similarly happens for the decrement operator.

B) Binary Operators: These operators operate or work with two operands. For example: Addition(+), Subtraction(-), etc.

Name	Symbol	Description	Example
Addition	+	Adds two operands	int a = 3, b = 6; int c = a+b; // c = 9
Subtraction	–	Subtracts second operand from the first	int a = 9, b = 6; int c = a-b; // c = 3
Multiplication	*	Multiplies two operands	int a = 3, b = 6; int c = a*b; // c = 18
Division	/	Divides first operand by the second operand	int a = 12, b = 6; int c = a/b; // c = 2
Modulo Operation	%	Returns the remainder an integer division	int a = 8, b = 6; int c = a%b; // c = 2

Note: The Modulo operator(%) operator should only be used with integers.

Example:

• C++

// CPP Program to demonstrate the Binary Operators #include <iostream> using namespace std;   int main() {     int a = 8, b = 3;       // Addition operator     cout << "a + b = " << (a + b) << endl;         // Subtraction operator     cout << "a - b = " << (a - b) << endl;         // Multiplication operator     cout << "a * b = " << (a * b) << endl;         // Division operator     cout << "a / b = " << (a / b) << endl;         // Modulo operator     cout << "a % b = " << (a % b) << endl;       return 0; }

Output

a + b = 11
a - b = 5
a * b = 24
a / b = 2
a % b = 2

Time Complexity: O(1)
Auxiliary Space : O(1)

2) Relational Operators

These operators are used for the comparison of the values of two operands. For example, ‘>’ checks if one operand is greater than the other operand or not, etc. The result returns a Boolean value, i.e., true or false.

Name	Symbol	Description	Example
Is Equal To	==	Checks if both operands are equal	int a = 3, b = 6; a==b;  // returns false
Greater Than	>	Checks if first operand is greater than the second operand	int a = 3, b = 6; a>b;  // returns false
Greater Than or Equal To	>=	Checks if first operand is greater than or equal to the second operand	int a = 3, b = 6; a>=b;  // returns false
Less Than	<	Checks if first operand is lesser than the second operand	int a = 3, b = 6; a<b;  // returns true
Less Than or Equal To	<=	Checks if first operand is lesser than or equal to the second operand	int a = 3, b = 6; a<=b;  // returns true
Not Equal To	!=	Checks if both operands are not equal	int a = 3, b = 6; a!=b;  // returns true

Example:

• C++

// CPP Program to demonstrate the Relational Operators #include <iostream> using namespace std;   int main() {     int a = 6, b = 4;       // Equal to operator     cout << "a == b is " << (a == b) << endl;         // Greater than operator     cout << "a > b is " << (a > b) << endl;         // Greater than or Equal to operator     cout << "a >= b is " << (a >= b) << endl;         //  Lesser than operator     cout << "a < b is " << (a < b) << endl;         // Lesser than or Equal to operator     cout << "a <= b is " << (a <= b) << endl;         // true     cout << "a != b is " << (a != b) << endl;       return 0; }

Output

a == b is 0
a > b is 1
a >= b is 1
a < b is 0
a <= b is 0
a != b is 1

Time Complexity: O(1)
Auxiliary Space : O(1)

Here, 0 denotes false and 1 denotes true. To read more about this, please refer to the article – Relational Operators.

3) Logical Operators

These operators are used to combine two or more conditions or constraints or to complement the evaluation of the original condition in consideration. The result returns a Boolean value, i.e., true or false.

Name	Symbol	Description	Example
Logical AND	&&	Returns true only if all the operands are true or non-zero	int a = 3, b = 6; a&&b; // returns true
Logical OR	||	Returns true if either of the operands is true or non-zero	int a = 3, b = 6; a||b; // returns true
Logical NOT	!	Returns true if the operand is false or zero	int a = 3; !a; // returns false

Example:

• C++

// CPP Program to demonstrate the Logical Operators #include <iostream> using namespace std;   int main() {     int a = 6, b = 4;       // Logical AND operator     cout << "a && b is " << (a && b) << endl;         // Logical OR operator     cout << "a ! b is " << (a > b) << endl;         // Logical NOT operator     cout << "!b is " << (!b) << endl;       return 0; }

Output

a && b is 1
a ! b is 1
!b is 0

Time Complexity: O(1)
Auxiliary Space : O(1)

Here, 0 denotes false and 1 denotes true. To read more about this, please refer to the article – Logical Operators.

4) Bitwise Operators

These operators are used to perform bit-level operations on the operands. The operators are first converted to bit-level and then the calculation is performed on the operands. Mathematical operations such as addition, subtraction, multiplication, etc. can be performed at the bit level for faster processing. 

Name	Symbol	Description	Example
Binary AND	&	Copies a bit to the evaluated result if it exists in both operands	int a = 2, b = 3; (a & b); //returns 2
Binary OR	|	Copies a bit to the evaluated result if it exists in any of the operand	int a = 2, b = 3; (a | b); //returns 3
Binary XOR	^	Copies the bit to the evaluated result if it is present in either of the operands but not both	int a = 2, b = 3; (a ^ b); //returns 1
Left Shift	<<	Shifts the value to left by the number of bits specified by the right operand.	int a = 2, b = 3; (a << 1); //returns 4
Right Shift	>>	Shifts the value to right by the number of bits specified by the right operand.	int a = 2, b = 3; (a >> 1); //returns 1
One’s Complement	~	Changes binary digits 1 to 0 and 0 to 1	int b = 3; (~b); //returns -4

Note: Only char and int data types  can be used with Bitwise Operators.

Example:

• C++

// CPP Program to demonstrate the Bitwise Operators #include <iostream> using namespace std;   int main() {     int a = 6, b = 4;       // Binary AND operator     cout << "a & b is " << (a & b) << endl;       // Binary OR operator     cout << "a | b is " << (a | b) << endl;       // Binary XOR operator     cout << "a ^ b is " << (a ^ b) << endl;       // Left Shift operator     cout << "a>>1 is " << (a >> 1) << endl;       // Right Shift operator     cout << "a<<1 is " << (a << 1) << endl;       // One’s Complement operator     cout << "~(a) is " << ~(a) << endl;       return 0; }

Output

a & b is 4
a | b is 6
a ^ b is 2
a>>1 is 3
a<<1 is 12
~(a) is -7

Time Complexity: O(1)
Auxiliary Space : O(1)

To read more about this, please refer to the article – Bitwise Operators.

5) Assignment Operators

These operators are used to assign value to a variable. The left side operand of the assignment operator is a variable and the right side operand of the assignment operator is a value. The value on the right side must be of the same data type as the variable on the left side otherwise the compiler will raise an error. 

Name	Symbol	Description	Example
Assignment Operator	=	Assigns the value on the right to the variable on the left	int a = 2;  // a = 2
Add and Assignment Operator	+=	First adds the current value of the variable on left to the value on the right and then assigns the result to the variable on the left	int a = 2, b = 4; a+=b; // a = 6
Subtract and Assignment Operator	-=	First subtracts the value on the right from the current value of the variable on left and then assign the result to the variable on the left	int a = 2, b = 4; a-=b; // a = -2
Multiply and Assignment Operator	*=	First multiplies the current value of the variable on left to the value on the right and then assign the result to the variable on the left	int a = 2, b = 4; a*=b; // a = 8
Divide and Assignment Operator	/=	First divides the current value of the variable on left by the value on the right and then assign the result to the variable on the left	int a = 4, b = 2; a /=b; // a = 2

Example:

• C++

// CPP Program to demonstrate the Assignment Operators #include <iostream> using namespace std;   int main() {     int a = 6, b = 4;       // Assignment Operator     cout << "a = " << a << endl;         //  Add and Assignment Operator     cout << "a += b is " << (a += b) << endl;         // Subtract and Assignment Operator     cout << "a -= b is " << (a -= b) << endl;         //  Multiply and Assignment Operator     cout << "a *= b is " << (a *= b) << endl;         //  Divide and Assignment Operator     cout << "a /= b is " << (a /= b) << endl;       return 0; }

Output

a = 6
a += b is 10
a -= b is 6
a *= b is 24
a /= b is 6

Time Complexity: O(1)
Auxiliary Space : O(1)

6) Ternary or Conditional Operators(?:)

This operator returns the value based on the condition. 

Expression1? Expression2: Expression3

The ternary operator ? determines the answer on the basis of the evaluation of Expression1. If it is true, then Expression2 gets evaluated and is used as the answer for the expression. If Expression1 is false, then Expression3 gets evaluated and is used as the answer for the expression.

This operator takes three operands, therefore it is known as a Ternary Operator. 

Example:

• C++

// CPP Program to demonstrate the Conditional Operators #include <iostream> using namespace std;   int main() {     int a = 3, b = 4;       // Conditional Operator     int result = (a < b) ? b : a;     cout << "The greatest number is " << result << endl;       return 0; }

Output

The greatest number is 4

Time Complexity: O(1)
Auxiliary Space : O(1)

7) There are some other common operators available in C++ besides the operators discussed above. Following is a list of these operators discussed in detail:

A) sizeof Operator: This unary operator is used to compute the size of its operand or variable.

sizeof(char); // returns 1

B) Comma Operator(,): This binary operator (represented by the token) is used to evaluate its first operand and discards the result, it then evaluates the second operand and returns this value (and type). It is used to combine various expressions together.

int a = 6;
int b = (a+1, a-2, a+5); // b = 10

C)  -> Operator: This operator is used to access the variables of classes or structures.

cout<<emp->first_name;

D) Cast Operator: This unary operator is used to convert one data type into another.

float a = 11.567;
int c = (int) a; // returns 11

E) Dot Operator(.): This operator is used to access members of structure variables or class objects in C++.

cout<<emp.first_name;

F) & Operator: This is a pointer operator and is used to represent the memory address of an operand.

G) * Operator: This  is an Indirection Operator

• C++

// CPP Program to demonstrate the & and * Operators #include <iostream> using namespace std;   int main() {     int a = 6;     int* b;     int c;     //  & Operator     b = &a;       // * Operator     c = *b;     cout << " a = " << a << endl;     cout << " b = " << b << endl;     cout << " c = " << c << endl;       return 0; }

Output

 a = 6
 b = 0x7ffe8e8681bc
 c = 6

H) << Operator: This is the output operator. It prints the output value.

I) >> Operator: This is the input operator. It gets the input value.

int a;
cin>>a;
cout<<a;

Time Complexity: O(1)
Auxiliary Space : O(1)

Operator Precedence Chart

Precedence	Operator	Description	Associativity
1.	()	Parentheses (function call)	left-to-right
	[]	Brackets (array subscript)
	.	Member selection via object name
	->	Member selection via a pointer
	++/–	Postfix increment/decrement
2.	++/–	Prefix increment/decrement	right-to-left
	+/-	Unary plus/minus
	!~	Logical negation/bitwise complement
	(type)	Cast (convert value to temporary value of type)
	*	Dereference
	&	Address (of operand)
	sizeof	Determine size in bytes on this implementation
3.	*,/,%	Multiplication/division/modulus	left-to-right
4.	+/-	Addition/subtraction	left-to-right
5.	<< , >>	Bitwise shift left, Bitwise shift right	left-to-right
6.	< , <=	Relational less than/less than or equal to	left-to-right
	> , >=	Relational greater than/greater than or equal to	left-to-right
7.	== , !=	Relational is equal to/is not equal to	left-to-right
8.	&	Bitwise AND	left-to-right
9.	^	Bitwise exclusive OR	left-to-right
10.	|	Bitwise inclusive OR	left-to-right
11.	&&	Logical AND	left-to-right
12.	||	Logical OR	left-to-right
13.	?:	Ternary conditional	right-to-left
14.	=	Assignment	right-to-left
	+= , -=	Addition/subtraction assignment
	*= , /=	Multiplication/division assignment
	%= , &=	Modulus/bitwise AND assignment
	^= , |=	Bitwise exclusive/inclusive OR assignment
	<>=	Bitwise shift left/right assignment
15.	,	expression separator	left-to-right

2.DATA TYPES

All variables use data type during declaration to restrict the type of data to be stored. 

• Data types are used to tell the variables the type of data they can store. Whenever a variable is defined in C++, the compiler allocates some memory for that variable based on the data type with which it is declared.
• Every data type requires a different amount of memory. 
• Data types specify the size and types of values to be stored.

C++ supports the following data types:

1. Primary or Built-in or Fundamental data type
2. Derived data types
3. User-defined data types

Data Types in C++ are Mainly Divided into 3 Types: 

1. Primitive Data Types: These data types are built-in or predefined data types and can be used directly by the user to declare variables. example: int, char, float, bool, etc. Primitive data types available in C++ are: 

• Integer
• Character
• Boolean
• Floating Point
• Double Floating Point
• Valueless or Void
• Wide Character

2. Derived Data Types: Derived data types that are derived from the primitive or built-in datatypes are referred to as Derived Data Types. These can be of four types namely: 

• Function
• Array
• Pointer
• Reference

3. Abstract or User-Defined Data Types: Abstract or User-Defined data types are defined by the user itself. Like, defining a class in C++ or a structure. C++ provides the following user-defined datatypes:  

• Class
• Structure
• Union
• Enumeration
• Typedef defined Datatype

Primitive Data Types

• Integer: The keyword used for integer data types is int. Integers typically require 4 bytes of memory space and range from -2147483648 to 2147483647.  
• Character: Character data type is used for storing characters. The keyword used for the character data type is char. Characters typically require 1 byte of memory space and range from -128 to 127 or 0 to 255.  
• Boolean: Boolean data type is used for storing Boolean or logical values. A Boolean variable can store either true or false. The keyword used for the Boolean data type is bool. 
• Floating Point: Floating Point data type is used for storing single-precision floating-point values or decimal values. The keyword used for the floating-point data type is float. Float variables typically require 4 bytes of memory space. 
• Double Floating Point: Double Floating Point data type is used for storing double-precision floating-point values or decimal values. The keyword used for the double floating-point data type is double. Double variables typically require 8 bytes of memory space. 
• void: Void means without any value. void data type represents a valueless entity. A void data type is used for those function which does not return a value. 
• Wide Character: Wide character data type is also a character data type but this data type has a size greater than the normal 8-bit data type. Represented by wchar_t. It is generally 2 or 4 bytes long.
• sizeof() operator: sizeof() operator is used to find the number of bytes occupied by a variable/data type in computer memory.

Example:

int m , x[50];     

cout<<sizeof(m); //returns 4 which is the number of bytes occupied by the integer variable “m”.  

cout<<sizeof(x); //returns 200 which is the number of bytes occupied by the integer array variable “x”.     

The size of variables might be different from those shown in the above table, depending on the compiler and the computer you are using.

• C++

// C++ Program to Demonstrate the correct size // of various data types on your computer. #include <iostream> using namespace std;   int main() {     cout << "Size of char : " << sizeof(char) << endl;     cout << "Size of int : " << sizeof(int) << endl;       cout << "Size of long : " << sizeof(long) << endl;     cout << "Size of float : " << sizeof(float) << endl;       cout << "Size of double : " << sizeof(double) << endl;       return 0; }

Output

Size of char : 1
Size of int : 4
Size of long : 8
Size of float : 4
Size of double : 8

 

Time Complexity: O(1)

Space Complexity: O(1)