A while loop in C programming
repeatedly executes a target
statement as long as a given
condition is true.
A while loop in C programming
repeatedly executes a target
statement as long as a given
condition is true.
3. WHILE LOOP
• A while loop in C programming
repeatedly executes a target
statement as long as a given
condition is true.
3
4. WHILE LOOP
• Syntax :
While (Test Expression)
{
// statements inside the body of the loop
}
4
5. WHILE LOOP
How While loop works :
• The while loop evaluates the test expression inside the parenthesis ().
• If the test expression is true, statements inside the body of while loop are
executed. Then, the test expression is evaluated again.
• The process goes on until the test expression is evaluated to false.
• If the test expression is false, the loop terminates (ends).
5
6. WHILE LOOP
// Print numbers from 1 to 5
#include <stdio.h>
int main()
{
int i = 1;
while (i <= 5)
{
printf("%dn", i);
++i;
}
return 0;
}
Here, we have initialized i to 1.
• When i is 1, the test expression i <= 5 is
true. Hence, the body of the while loop is
executed. This prints 1 on the screen
and the value of i is increased to 2.
• Now, i is 2, the test expression i <= 5 is
again true. The body of the while loop is
executed again. This prints 2 on the
screen and the value of is increased
to 3.
• This process goes on until i becomes 6.
When i is 6, the test expression i<=5 will
be false and the loop terminates.
6
Output :
1
2
3
4
5
7. DO...WHILE LOOP
• The do..while loop is similar to
the while loop with one important
difference.
• The body of do...while loop is
executed at least once. Only then,
the test expression is evaluated.
7
8. DO...WHILE LOOP
• Syntax :
do
{
// statements inside the body of the loop
} while (Test Expression);
8
9. DO...WHILE LOOP
How Do...While loop works :
• The body of do...while loop is executed once. Only then, the test expression
is evaluated.
• If the test expression is true, the body of the loop is executed again and the
test expression is evaluated.
• This process goes on until the test expression becomes false.
• If the test expression is false, the loop ends.
9
10. DO...WHILE LOOP
// Print numbers from 1 to 5
#include <stdio.h>
int main()
{
int i = 1;
do
{
printf("%dn", i);
++i;
} while(i <= 5) ;
return 0;
}
Here, we have initialized i to 1.
• As we know that do…while loop is
executed at least one time, it will be
printed when i=1 and then i
increments to 2.
• Now, i is 2, the test expression i <=
5 is true. The body of the do…while
loop is executed again. This prints 2
on the screen and the value of i is
increased to 3.
• This process goes on until i becomes
6. When i is 6, the test
expression i<=5 will be false and the
loop terminates.
10
Output :
1
2
3
4
5
11. SWITCH STATEMENTS
• The switch statement allows us to
execute one code block among many
alternatives.
• You can do the same thing with
the if...else..if ladder. However, the
syntax of the switch statement is
much easier to read and write.
11
13. SWITCH STATEMENTS
How switch case works :
• The expression is evaluated once and compared with the values of
each case label.
• If there is a match, the corresponding statements after the matching label are
executed. For example, if the value of the expression is equal to constant2,
statements after case constant2: are executed until break is encountered.
• If there is no match, the default statements are executed.
• If we do not use break, all statements after the matching label are executed.
• By the way, the default clause inside the switch statement is optional.
13
14. 14
• In the given program we have
initialized a variable x with value 2.
• A switch construct is used to compare
the value stored in variable x and
execute the block of statements
associated with the matched case.
• In this program, since the value stored
in variable x is two, a switch will
execute the case whose case-label is 2.
After executing the case, the control
will fall out of the switch and program
will be terminated with the successful
result by printing the value on the
output screen.
// Following is a simple C program to
demonstrate syntax of switch.
#include <stdio.h>
int main()
{
int x = 2;
switch (x)
{
case 1:
printf("Choice is 1");
break;
case 2:
printf("Choice is 2");
break;
case 3:
printf("Choice is 3");
break;
default:
printf("Choice other than 1, 2 and 3");
break;
}
return 0;
}
16. FOR LOOP
• Loop Concept
Loop is a repetition for series of actions and
activities.
In programming sometimes we need to repeat
block or statement for some period.
Loop is helping to repeat particular block or set
of statements for particular time period.
When to stop looping?
In chart , action is executed over and over again.
It never stop – This is called an Infinite Loop
Solution – Put a condition to tell the loop either
to continue or stop
2
An actions
and activities
or series of
actions and
activities
17. CONTINUE…
Main part of loop : Body and Condition
Body : Statement or Block of statements that will
be repeated.
Condition : It is used to control iteration either to
continue or stop the iteration.
3
Body Of Loop
Condi
tion
True
False
18. PRE-TEST LOOP
Condition is tested First before start executing
the body.
Body of the loop will executed if the condition is
true.
If condition becomes false loop will terminate.
After executing body again condition is tested.
4
Body Of Loop
Condi
tion
False
Pre-test Loop (FOR LOOP)
True
Stop
19. FOR LOOP
The for loop in C language is used to repeat the
statements or a block of the program several times.
The syntax of for loop in c language is given below:
for( Initialization ; Condition ; Increment or Decrement )
{
Statement block to be executed ;
}
Loop Execution :
Step 1: First initialization happens and the counter
variable gets initialized. Execute only One time.
Step 2: In the second step the condition is checked, if
the condition is true then the C statements inside the
body of for loop gets executed, if the condition is false
then the for loop gets terminated.
Step 3: After successful execution of statements inside
the body of loop, the counter variable is incremented or
decremented, depending on the operation (++ or –-).
5
Initialization
Condition
Statement
Incr / Decr
True
False
Stop
FOR Loop
Flow Chart
20. WHILE LOOP
for (
)
FOR LOOP
COMPARING FOR AND WHILE
6
Initialize
While (Expression)
{
} /* While */
action
action
update counter
Initialize;
Condition;
Increment or
Decrement;
{
} /* For */
action
action
action
Continue…
Continue…
21. FOR LOOP EXAMPLE 1
// Print numbers from 1 to 10
#include <stdio.h>
int main() {
int i;
for (i = 1; i < 11; ++i)
{
printf("%d ", i);
}
return 0;
}
O / P :
1 2 3 4 5 6 7 8 9 10
7
1. i is initialized to 1.
2. The test expression i < 11 is evaluated.
Since 1 less than 11 is true, the body
of for loop is executed. This will print
the 1 (value of i) on the screen.
3. The update statement ++i is executed.
Now, the value of i will be 2. Again, the test
expression is evaluated to true, and the
body of for loop is executed. This will
print 2 (value of i) on the screen.
4. Again, the update statement ++i is
executed and the test expression i < 11 is
evaluated. This process goes on
until i becomes 11.
5. When i becomes 11, i < 11 will be false,
and the for loop terminates.
22. FOR LOOP EXAMPLE 2
#include <stdio.h>
int main()
{ int num, count, sum = 0;
printf("Enter a positive integer: ");
scanf("%d", &num);
for(count = 1; count <= num; ++count)
{
sum += count;
}
printf("Sum = %d", sum);
return 0;
}
O/P :
Enter a positive integer: 5
Sum = 15
8
The value entered by the user is stored in the
variable num. Suppose, the user entered 5.
The count is initialized to 1 and the test expression is
evaluated. Since the test expression count<=num (1
less than or equal to 5) is true, the body of for loop is
executed and the value of sum will equal to 1.
Then, the update statement ++count is executed and
the count will equal to 2. Again, the test expression is
evaluated. Since 2 is also less than 5, the test
expression is evaluated to true and the body of for loop
is executed. Now, the sum will equal 3.
This process goes on and the sum is calculated until
the count reaches 6.
When the count is 6, the test expression is evaluated to
false, and the loop terminates.
Then, the value of sum is printed on the screen.
23. VARIOUS FORMS OF FOR LOOP IN C
Suppose we are using variable num as the counter in all the following examples –
1) Here instead of num++, I’m using num=num+1 which is same as num++.
for (num=10; num<20; num=num+1)
2) Initialization part can be skipped from loop as shown below, the counter variable is declared
before the loop.
int num=10;
for ( ; num<20;num++)
Note: Even though we can skip initialization part but semicolon (;) before condition is must,
without which you will get compilation error.
3) Like initialization, you can also skip the increment part as we did below. In this case
semicolon (;) is must after condition logic. In this case the increment or decrement part is done
inside the loop.
for (num=10; num<20; )
{ //Statements
num++;
}
9
24. CONTINUE….
4) This is also possible. The counter variable is initialized before the loop and incremented
inside the loop.
int num=10;
for (;num<20;)
{
//Statements
num++;
}
5) As mentioned above, the counter variable can be decremented as well. In the below example
the variable gets decremented each time the loop runs until the condition num>10 returns false.
for(num=20; num>10; num--)
10
25. NESTED LOOPS IN C
• C supports nesting of loops. Nesting of loops is the feature that allows the
looping of statements inside another loop.
• Any number of loops can be defined inside another loop, i.e., there is no
restriction for defining any number of loops. The nesting level can be defined at
n times.
Syntax for Nested Looping :
Outer_loop
{
Inner_loop
{
// inner loop statements.
}
// outer loop statements.
}
11
26. NESTED FOR LOOP
The nested for loop means for loop which is
defined inside the another 'for' loop.
for (initialization; condition; increment or
decrement)
{
for(initialization; condition; increment or
decrement)
{
// inner loop statements.
}
// outer loop statements.
}
12
Nested For loop Flow Chart :
27. NESTED FOR LOOP EXAMPLE
#include <stdio.h>
int main(void)
{ int i,j;
for(i=0;i<5;i++)
{
for(j=0;j<=i;j++)
{
printf(" *");
}
printf("n");
}
return 0;
}
O/P : *
* *
* * *
* * * *
* * * * *
13
First, the 'i' variable is initialized to 1 and then program control
passes to the i<5.
The program control checks whether the condition 'i<5' is true or not.
If the condition is true, then the program control passes to the inner
loop.
The inner loop will get executed until the condition is true.
After the execution of the inner loop, the control moves back to the
update of the outer loop, i.e., i++.
After incrementing the value of the loop counter, the condition is
checked again, i.e., i<5.
If the condition is true, then the inner loop will be executed again.
This process will continue until the condition of the outer loop is true.
32. 5
Nested If..else
If..else Statement
Simple if Statement
Let us Enter Value : 50
Let us Enter Value : 55
Let us Enter Values : 45, 56 and 89
Examples : Simple if , else… if , nested if…else, if..else…if Ladder
35. CHAPTER 3 TOPIC 1
• INTRODUCTION
• Control Statement
• Simple Statement
• Decision Making Statement
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
22-10-2020 2
36. INTRODUCTION
• In any programming language, there is a
need to perform different tasks based
on the condition.
• For example, consider example of true
and false if your answer is right you will
get 1 point and if answer is wrong you
will get 0.
• Behind process conditional logic
declared in any programming language
it’s called the Control Statement.
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
22-10-2020 3
37. SIMPLE STATEMENT
22-10-2020
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
4
Entry
Action 1
Action 2
Action 3
Exit
• Simple statements are used in C or C++ for
unconditional flow of control through out the
functions in a program. They support Three type of
simple statements.
1. Break
2. Continue
3. Goto
38. DECISION MAKING STATEMENT
22-10-2020
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
5
• Decision making structures require that
the programmer specifies one or more
conditions to be evaluated or tested by the
program.
• statements to be executed if the condition
is determined to be true, and optionally,
other statements to be executed if the
condition is determined to be false.
• They support two type of decision
statements.
1. IF….ELSE
2. SWITCH
Action 1 Action 1
Condition
to make
Decision
EXIT
ENTRY
TRUE FALSE
39. BREAK
22-10-2020
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
6
Condition
to break
from loop
Action 1
TRUE
FALSE
Loop body
start
• Break statements are used in the
situations when we are not sure
about the actual number of
iterations for the loop or we want to
terminate the loop based on some
condition.
Syntax :- break;
40. BREAK EXAMPLE
22-10-2020
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
7
#include <stdio.h>
int main ()
{
/* local variable definition */
int a = 10;
/* while loop execution */
while( a < 20 )
{
printf("value of a: %dn", a);
a++;
if( a > 15)
{
/* terminate the loop using break statement */
break;
}
}
return 0;}
Output
value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
41. CONTINUE
• This loop control statement is just
like the break statement. The
continue statement is opposite to
that of break statement, instead of
terminating the loop, it forces to
execute the next iteration of the
loop.
22-10-2020
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
8
Syntax :-
continue;
Condition
to continue
next
iteration
Action 1
TRUE
FALSE
Loop body
start
Execute remaining
part of body loop
42. #include <stdio.h>
int main ()
{
/* local variable definition
*/
int a = 10;
/* do loop execution */
do {
if( a == 15)
{
22-10-2020
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
9
CONTINUE EXAMPLE
/* skip the iteration */
a = a + 1;
continue;
}
printf("value of a: %dn", a);
a++;
}
while( a < 20 );
return 0;}
Output
value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 16
value of a: 17
value of a: 18
value of a: 19
43. GO TO STATEMENT
22-10-2020
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
10
start
Statement 1
Statement 2
Statement 3
Label 1
Label 2
Label 3
start
stop
• The goto statement in C/C++ also
referred to as unconditional jump
statement can be used to jump from
one point to another within a
function.
goto label;
..
.
label: statement;
44. #include <stdio.h>
int main ()
{
/* local variable definition */
int a = 10;
/* do loop execution */
LOOP:do {
if( a == 15)
{
22-10-2020
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
11
GO TO EXAMPLE
/* skip the iteration */
a = a + 1;
goto LOOP;
}
printf("value of a: %dn", a);
a++;
}while( a < 20 );
return 0;
}
Output
value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 16
value of a: 17
value of a: 18
value of a: 19
45. 22-10-2020
DEPARTMENT OF COMPUTER ENGINEERING & INFORMATION TECHNOLOGY
*Proprietary material of SILVER OAK UNIVERSITY
12
REFERENCE
For Theory
• https://www.geeksforgeeks.org/continue-statement-cpp/?ref=lbp
• https://en.wikibooks.org/wiki/C_Programming/Statements
• https://www.geeksforgeeks.org/break-statement-cc/?ref=lbp
• https://www.tutorialspoint.com/cprogramming/c_decision_making.htm
NPTEL
• https://youtu.be/BZwdn-t_unY
• https://youtu.be/CxkPH74fVBo
