1. CONTENTS Loop Statements Parts of a loop Types of Loops Nested Loops
While Loop
For Loop
Do-while Loop
Nested Loops
Jump Statements
Exercises

2. LOOP STATEMENTS
The loop statements allow a set of instructions to be performed repeatedly until a certain condition is fulfilled. Following is the general from of a loop statement in most of the programming languages:

3. PARTS OF A LOOP
Initialization Expression(s) initialize(s) the loop variables in the beginning of the loop.
Test Expression decides whether the loop will be executed (if test expression is true) or not (if test expression is false).
Update Expression(s) update(s) the values of loop variables after every iteration of the loop.
The Body-of-the-Loop contains statements to be executed repeatedly.

4. TYPES OF LOOPS
C++ programming language provides following types of loop to handle looping requirements:
Loop Type
Description
while loop
Repeats a statement or group of statements until a given condition is true. It tests the condition before executing the loop body.
for loop
Execute a sequence of statements multiple times and abbreviates the code that manages the loop variable.
do...while loop
Like a while statement, except that it tests the condition at the end of the loop body
nested loops
You can use one or more loop inside any another while, for or do..while loop.

5. WHILE LOOP The syntax of while statement :
while (loop repetition condition)
statement
Loop repetition condition is the condition which controls the loop.
The statement is repeated as long as the loop repetition condition is true.
A loop is called an infinite loop if the loop repetition condition is always true.

7. Logic of a while Loop
condition
evaluated
false
statement
true

8. EXAMPLE: cout<<“\n”<<j; #include<iostream.h>
#include <stdio.h>
int main(void) {
      int j;
      j = -5;
      // while loop
      while(j <= 0)
      {
cout<<“\n”<<j;          
   j= j + 1;
      }
      return 0; }

9. FOR LOOP A for statement has the following syntax:
The initialization
is executed once
before the loop begins
The statement is
executed until the
condition becomes false
for ( initialization ; condition ; increment ) {
statement; }
The increment portion is executed at the end of each iteration

11. Logic of a for loop initialization condition evaluated false true
statement
true
increment

12. EXAMPLE: OUTPUT Enter number: 3 3*1=3 3*2=6 3*3=9 3*4=12 3*5=15 3*6=18
//program to display table of a given number using for loop. #include<iostream.h> void main() { int n; cout<<“\n Enter number:”; cin>>n; //for loop for(int i=1;i<11;++i) cout<<“\n”<<n<<“*”<<i<<“=“<<n*i; }
Enter number: 3
3*1=3
3*2=6
3*3=9
3*4=12
3*5=15
3*6=18
3*7=21
3*8=24
3*9=27
3*10=30

13. THE FOR LOOP VARIATIONS
Multiple initialization and update expressions
A for loop may contain multiple initialization and/or multiple update expressions. These multiple expressions must be separated by commas.
e.g.
for( i=1, sum=0; i<=n; sum+=i, ++i)
cout<<“\n”<<i;

14. Prefer prefix increment/decrement over postfix when to be used alone.
for( i=1;i<n;++i) :
rather than,
for( i=1;i<5;i++)
Reason being that when used alone ,prefix operators are faster executed than postfix.
Prefer this over this

15. Infinite loop
An infinite loop can be created by omitting the test expression as shown:
for(j=25; ;--j)
cout<<“an infinite for loop”;
An infinite loop can also be created as:
for( ; ; )
cout<<“endless for loop”;

16. Empty loop
If a loop does not contain any statement in its loop-body, it is said to be an empty loop:
for(j=25; (j) ;--j) //(j) tests for non zero value of j.
If we put a semicolon after for’s parenthesis it repeats only for counting the control variable. And if we put a block of statements after such a loop, it is not a part of for loop.
e.g. for(i=0;i<10;++i); {
cout<<“i=“<<i<<endl; }
The semicolon ends the loop here only
This is not the body of the for loop. For loop is an empty loop

17. DO…WHILE LOOP The syntax of do-while statement in C:
do statement while (loop repetition condition);
The statement is first executed.
If the loop repetition condition is true, the statement is repeated.
Otherwise, the loop is exited.

18. Logic of a do…while loop
statement
true
condition
evaluated
false

19. EXAMPLE:
OUTPUT
//program to display counting from 1 to 10 using do-while loop. #include<iostream.h> void main() { int i=1; //do-while loop do cout<<“\n”<<i; i++; }while(i<=10); } 1 2 3 4 5 6 7 8 9 10

20. NESTED LOOPS
Nested loops consist of an outer loop with one or more inner loops.
e.g.,
for (i=1;i<=100;i++){
for(j=1;j<=50;j++){ … }
The above loop will run for 100*50 iterations.
Outer loop
Inner loop

21. * * * * * * * * * * EXAMPLE: OUTPUT
//program to display a pattern of a given character using nested loop. #include<iostream.h> void main() { int i,j; for( i=1;i<5;++i) cout<<“\n”; for(j=1;j<=i;++j) cout<<“*”; }
OUTPUT *
* *
* * *
* * * *

22. JUMP STATEMENTS The goto statement
A goto statement can transfer the program control anywhere in the program.
The target destination is marked by a label.
The target label and goto must appear in the same statement.
The syntax of goto statement is:
goto label; …
label:

23. The break statement
The break statement enables a program to skip over part of the code.
A break statement terminates the smallest enclosing while, do-while and for statements.
A break statement skips the rest of the loop and jumps over to the statement following the loop.
The following figures explains the working of a break statement :

24. for(initialize;test expression;update){
statement1;
if(val>2000)
break; :
statement2; }
statement3;
WORKING OF BREAK STATEMENT IN FOR LOOP

25. while(test expression) { statement1; if(val>2000) break; : statement2; } statement3;
WORKING OF BREAK STATEMENT IN WHILE LOOP

26. do { statement1; if(val>2000) break; : statement2; } while(test expression) statement3;
WORKING OF BREAK STATEMENT IN DO-WHILE LOOP

27. The continue statement
The continue statement works somewhat like the break statement.
For the for loop, continue causes the conditional test and increment portions of the loop to execute. For the while and do...while loops, program control passes to the conditional tests.
Syntax:
The syntax of a continue statement in C++ is:
continue;

28. EXERCISES:
MULTIPLE CHOICE QUESTIONS (MCQs)
PROGRAM BASED QUESTIONS

29. MCQs...

30. 1. The statement i++; is equivalent to [a] i = i + i; [b] i = i + 1; [c] i = i - 1; [d] i --;
ANS: [b]
NEXT QUESTION

31. 2. What's wrong? for (int k = 2, k <=12, k++) [a] the increment should always be ++k [b] the variable must always be the letter i when using a for loop [c] there should be a semicolon at the end of the statement [d] the commas should be semicolons
ANS: [d]
NEXT QUESTION

32. 3. Which looping process checks the test condition at the end of the loop? [a] for [b] while [c] do-while [d] no looping process checks the test condition at the end
ANS: [c]
NEXT QUESTION

33. 4. Which looping process is best used when the number of iterations is known? [a] for [b] while [c] do-while [d] all looping processes require that the iterations be known
ANS: [a]
NEXT QUESTION

34. 5. A continue statement causes execution to skip to [a] the return 0; statement [b] the first statement after the loop [c] the statement following the continue statement [d] the next iteration of the loop
ANS: [d]

35. PROGRAM BASED QUESTIONS…

36. Write a program to print first n natural numbers and their sum.
Write a program to calculate the factorial of an integer.
Write a program that prints
Write a program to check whether the given number is palindrome or not.
Write a program to generate divisors of an integer.
Write a program to find whether a given number is odd or even. The program should continue as long as the user wants.
Write a program to print Fibonacci series i.e., ….

37. Write a program to print largest even and largest odd number from a list of numbers entered. The list terminates as soon as one enters 0(zero).
Write a program to check whether the entered number is Armstrong or not.
Write a program to display Pythagorean triplets up to 100.
Write a program to calculate average of 10 numbers.
Write programs to produce the following designs: A
A B
A B C
A B C D
A B C D E

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39. THANK YOU