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Increment and Decrement operators in C++

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Neeru Mittal

The document discusses C++ increment and decrement operators. It explains that these unary operators work only on integers, and can be used in both prefix (++a) and postfix (a++) forms. In prefix form, the increment/decrement occurs before the expression is evaluated. In postfix form, it occurs after. The key difference is that prefix returns the new value, while postfix returns the original value. Several examples are provided to illustrate this behavior. Finally, some practice questions are included to help test understanding of these fundamental operators.

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C++ Increment / Decrement Operators Computer Science Class XI CBSE
Objectives At the end of this lesson students should be able to: Identify the increment/ decrement operators 1 Understand the working of the operators 2 Distinguish between the prefix and postfix forms 3 Evaluate different expressions containing these operators 4
How do they look like?
Increment(++) / Decrement(--) Operators The increment(++) and decrement(--) are unary operators that work only on integer variables. The syntax is : Examples: The increment / decrement operators do not work on constants. Thus : variable ++; or ++ variable; variable --; or -- variable; a++; ++ x; p=--q; t--; 6++; //gives error as 6 is a constant x=--9; // gives error as 9 is a constant
Increment(++) / Decrement(--) Operators The increment operator increases the value of a variable by 1 The decrement operator decreases the value of a variable by 1. Thus and a++; is the same as a=a+1; b--; is the same as b=b-1;
Both the increment and decrement operators can be prefixed or postfixed. i.e. In the above statements both prefix and postfix forms do not make any difference in the output as these are stand alone statements. But when the pre/post increment or decrement operators are part of an expression the prefix and postfix notation does matter Increment(++) / Decrement(--) Operators ++a; (prefix) is the same as a++; (postfix)
Increment(++) / Decrement(--) Operators Pre Increment int a,b; a=3; b=++a; cout<<“a= ”<<a<<“tb= ”<<b; In the prefix form the increment or decrement operation is carried out before the rest of the expression. Consider the following code snippet: a b a= 4 b= 4 1 2 output Working code Explanation
Increment(++) / Decrement(--) Operators Post Increment In the postfix form the increment or decrement operation is carried out after the rest of the expression. Consider the following code snippet: a b a= 4 b= 3 1 2 output Working Explanation code int a, b ; a=3; b=a++; cout<<“a= “<<a<<“tb= “<<b;
Thumb rule • Prefix: change and use CHANGE the Value of the variable USE the new value • Postfix : use and change • USE the original value of the variable • CHANGE the Value of the variable 1 1 2 2
Program to illustrate Increment, Decrement operators #include<iostream.h> void main() { int a,b,c,d; a = 0; b = 2; c = 4; d = a -- + b++ + ++c; cout<<“A= ”<<a<<“tB= ” <<b<<“tC= ”<<c“tD = "<<d; } A= -1 B= 3 C= 5 D= 7 0 2 4 a b c d d= a -- + b++ + ++c;
A video explaining the increment and decrement operators
TEST YOURSELF
Question 1
Question 2
Question 3 int x, y; x=0; y=x++; y--; --x; Consider the following code snippet and answer the question that follows :
Question 3
Question 4 Consider the following code and answer the question that follows : #include <iostream.h> void main() { int x = 4, y = 7, z; x = ++x; y = --y; z = x++ + y--; cout << z; }
Question 4
Question 5

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Increment and Decrement operators in C++

  • 1. C++ Increment / Decrement Operators Computer Science Class XI CBSE
  • 2. Objectives At the end of this lesson students should be able to: Identify the increment/ decrement operators 1 Understand the working of the operators 2 Distinguish between the prefix and postfix forms 3 Evaluate different expressions containing these operators 4
  • 3. How do they look like?
  • 4. Increment(++) / Decrement(--) Operators The increment(++) and decrement(--) are unary operators that work only on integer variables. The syntax is : Examples: The increment / decrement operators do not work on constants. Thus : variable ++; or ++ variable; variable --; or -- variable; a++; ++ x; p=--q; t--; 6++; //gives error as 6 is a constant x=--9; // gives error as 9 is a constant
  • 5. Increment(++) / Decrement(--) Operators The increment operator increases the value of a variable by 1 The decrement operator decreases the value of a variable by 1. Thus and a++; is the same as a=a+1; b--; is the same as b=b-1;
  • 6. Both the increment and decrement operators can be prefixed or postfixed. i.e. In the above statements both prefix and postfix forms do not make any difference in the output as these are stand alone statements. But when the pre/post increment or decrement operators are part of an expression the prefix and postfix notation does matter Increment(++) / Decrement(--) Operators ++a; (prefix) is the same as a++; (postfix)
  • 7. Increment(++) / Decrement(--) Operators Pre Increment int a,b; a=3; b=++a; cout<<“a= ”<<a<<“tb= ”<<b; In the prefix form the increment or decrement operation is carried out before the rest of the expression. Consider the following code snippet: a b a= 4 b= 4 1 2 output Working code Explanation
  • 8. Increment(++) / Decrement(--) Operators Post Increment In the postfix form the increment or decrement operation is carried out after the rest of the expression. Consider the following code snippet: a b a= 4 b= 3 1 2 output Working Explanation code int a, b ; a=3; b=a++; cout<<“a= “<<a<<“tb= “<<b;
  • 9. Thumb rule • Prefix: change and use CHANGE the Value of the variable USE the new value • Postfix : use and change • USE the original value of the variable • CHANGE the Value of the variable 1 1 2 2
  • 10. Program to illustrate Increment, Decrement operators #include<iostream.h> void main() { int a,b,c,d; a = 0; b = 2; c = 4; d = a -- + b++ + ++c; cout<<“A= ”<<a<<“tB= ” <<b<<“tC= ”<<c“tD = "<<d; } A= -1 B= 3 C= 5 D= 7 0 2 4 a b c d d= a -- + b++ + ++c;
  • 11. A video explaining the increment and decrement operators
  • 15. Question 3 int x, y; x=0; y=x++; y--; --x; Consider the following code snippet and answer the question that follows :
  • 17. Question 4 Consider the following code and answer the question that follows : #include <iostream.h> void main() { int x = 4, y = 7, z; x = ++x; y = --y; z = x++ + y--; cout << z; }