The document discusses control flow statements in C programming, including conditional statements like if, if-else, and nested if-else statements. It provides examples of using conditional logic to check if a number is divisible by 6, even or odd, or if a year is a leap year. The nested if-else statements can be used to find the largest of three numbers. Flowcharts and programs written in C are given as examples to illustrate how to use conditional statements to implement control flow and make decisions in a code based on different conditions.

1. 101903/CO200G
PROGRAMMING IN C
Module II
CONTROL FLOW STATEMENTS

2. 2
MODULE II - SYLLABUS
Program Basics
• Control Flow Statements: If Statement, Switch
Statement, Unconditional Branching using goto
statement, While Loop, Do While Loop, For Loop,
Break and Continue statements. (Simple programs
covering control flow)
Dept of IT, RSET

3. CO2: Develop readable* C programs with branching and
looping statements, which uses Arithmetic, Logical,
Relational or Bitwise operators.
COURSE OUTCOME

4. Conditional Statements

5. 1. Why Conditional Statements
2. if
3. if – else
4. Nested if - else
CONTENTS

6. • In everyday life, we make many decisions
• If it is raining, take an umbrella when you go
out
• If a polygon has 4 sides, it is a quadrilateral
• If some condition is true, do some action –
use conditional statements
Why Conditional Statements

7. • Used for branching
• A logical test is done, depending on the outcome of
the test, one of the several possible actions are
carried out
• Logical expressions are used to perform the test
• Logical expressions evaluates to true or false
• Also called selection, because a group of statements
is selected from several available groups
Conditional Statements

8. • To form logical expressions we use
– Four relational operators, <, <=, >, >=
– Two equality operators, ==, !=
– Logical connectives (logical operators), && (AND), ||
(OR) and ! (unary negation operator)
• Logical connectives are used to combine logical
expressions to form a complex expression
Logical Expressions

9. Conditional Statements
Conditional
Statements
if – else
Nested if –
else
Switch Goto

10. • Used to express decisions
• Conduct a logical test and perform an action if the
outcome of the test is true
If

11. if (expression)
{
statement 1;
}
statement x;
Syntax in C
Algorithm
Step no (e.g. 4) : If the condition <condition 1>
Step 4.1 : Then <statements>
Block Executed if the expression
is True

12. Step 1 : Start
Step 2 : Read the number
Step 3 : Assign the value of number into variable num
Step 4 : If the condition num % 6 is 0 then
Step 4.1 : Then print num is divisible by 6
Step 5 : Stop
Algorithm - Check whether a number is divisible by 6

13. Program to check if a number divisible by 6
#include <stdio.h>
int main()
{
int num;
printf("Enter a number");
scanf("%d", &num);
if(num%6 == 0)
{
printf("%d is divisible by 6",num);
}
return 0;
}

14. If you want to execute some code if a condition is
true and another code if a condition is false
If – Else

15. Syntax
if (expression)
{
statement 1;
}
else
{
statement 2;
}
statement x;
Block Executed if the expression
is True
Block Executed if the expression
is False

16. Algorithm
Step no (e.g. 4) : If the condition <condition 1>
Step 4.1 : Then <statements>
Step no (e.g. 5) : Otherwise
Step 5.1 : <statements>

17. Step 1 : Start
Step 2 : Read the numbers
Step 3 : Assign the value of number into variable num
Step 4 : If the condition num % 6 is 0
Step 4.1 : Then print num is divisible by 6
Step 5 : Otherwise
Step 5.1: Print num is not divisible by 6
Step 6 : Stop
Algorithm - Check whether a number is divisible by 6 or not

18. #include <stdio.h>
int main()
{
int num;
printf("Enter a number");
scanf("%d", &num);
if(num%6 == 0)
printf("%d is divisible by 6",num);
else
printf("%d is not divisible by 6",num);
return 0;
}
Program to check if a number divisible by 6 or not

19. Step 1 : Start
Step 2 : Read the number
Step 3 : Assign the value of number into variable num
Step 4 : If the condition num % 2 is 0
Step 4.1 : Then print the number num is even
Step 5 : Otherwise
Step 5.1 : Print the number num is odd
Step 6 : Stop
Algorithm - Check whether a number is even or odd

20. #include <stdio.h>
int main()
{
int num;
printf("Enter the number to check:");
scanf("%d",&num);
if(num%2 == 0)
printf("The number %d is even",num);
else
printf("The number %d is odd",num);
return 0;
}
Program to check if a number is even or odd

21. • Conditional operator ?: is equivalent to a simple if-
else structure
• It makes use of an expression that is either true or
false
• An appropriate value is selected depending on the
outcome of the expression
• A=(3<4)?(3+4):(8+2)
Conditional Operator

22. • It is possible to nest if - else statements one within
another
• Nested if – else statements can take several
different forms
• Multi-way decision
Nested If – Else Statements

23. If – Else If – Else (form 1)

24. if (expression 1)
{
statement 1;
}
else if (expression 2)
{
statement 2;
}
…
…
else if (expression n)
{
statement n;
}
else
{
statement n+1;
}
statement x;
Syntax

25. Algorithm
Step no (e.g. 4) : If the condition <condition 1>
Step 4.1 : Then <statements>
Step no (e.g. 5) : Otherwise If the condition <condition 2>
Step 5.1 : <statements>
Step no (e.g. 6) : Otherwise If the condition <condition n>
Step 6.1 : <statements>
Otherwise
Step 7.1 : <statements>

26. Step 1 : Start
Step 2 : Read the three numbers
Step 3 : Assign the value of first number into variable num1, the
value of second number into variable num2 and the value of third
number into variable num3
Step 4 : If the condition num1 is larger than num2 and num1 is
larger than num3
Step 4.1 : Then print num1 is the largest of three numbers
Step 5 : Otherwise If the condition num2 is larger than num1 and
num2 is larger than num3
Step 5.1 : Then print num2 is the largest of three numbers
Step 6 : Otherwise
Step 6.1 : Print num3 is the largest of three numbers
Step 7 : Stop
Algorithm - Largest of 3 numbers

27. #include <stdio.h>
int main()
{
int num1, num2, num3;
printf("Enter three numbers");
scanf("%d,%d,%d", &num1, &num2, &num3);
if(num1>num2 && num1>num3)
printf("%d is the largest of the three",num1);
else if(num2>num1 && num2>num3)
printf("%d is the largest of the three",num2);
else
printf("%d is the largest of the three",num3);
return 0;
}
Program to find the largest of three numbers

28. Algo2: to find the largest of three numbers
1.Start
2. Read the three numbers to be compared, as A, B and C. 3.
3.Check if A is greater than B.
3.1 check if A is greater than C.
3.1.1 Print 'A' as the greatest number.
3.2 otherwise,print 'C' as the greatest number.
3.3 Check if B is greater than C.
3.3.1 If true, print 'B' as the greatest number.
3.4 Otherwise, print 'C' as the greatest number.
4. End

29. Step 1: Start
Step 2: Read the year
Step 3: Assign the value into variable y
Step 4: If the condition y % 400 is 0
Step 4.1: Then print y is a leap year
Step 5: Otherwise If the condition y % 100 is 0
Step 5.1: Then print y is not a leap year
Step 6: Otherwise If the condition y % 4 is 0
Step 6.1: Then print y is a leap year
Step 7: Otherwise
Step 7.1: print y is not a leap year
Step 8 : Stop
Algorithm - Leap Year or not

30. #include <stdio.h>
int main() {
int year;
printf("Enter a year: ");
scanf("%d", &year);
// leap year if perfectly divisible by 400
if (year % 400 == 0)
{
printf("%d is a leap year.", year);
}
//not a leap year if divisible by 100
//but not divisible by 400
else if (year % 100 == 0)
{
printf("%d is not a leap year.", year);
}
Program to check if a given year is leap year or not

31. Cont…
// leap year if not divisible by 100
// but divisible by 4
else if (year % 4 == 0)
{
printf("%d is a leap year.", year);
}
// all other years are not leap years
else
{
printf("%d is not a leap year.", year);
}
return 0;
}

32. Nested If – Else Statement (form 2)
if (expression1)
{
if (expression2)
statement 1;
else
{
statement 2;
}
}
else if (expression3)
{
statement 3;
}
else
{
statement 4;
}

33. Nested If - Else
Step no (e.g. 4) : If the condition <condition 1>
Step 4.1 : If the condition <condition 2>
Step 4.1.1 : <statement 1>
step 4.2: Otherwise
Step 4.2.1 : <statement 2>
Otherwise
Step 5.1 : If the condition <condition 3>
Step 5.1.1 : <statement 3>
step 5.2: Otherwise
Step 5.2.1 : <statement 4>

34. Step 1 : Start
Step 2 : Read the three numbers
Step 3 : Assign the value of first number into variable num1,
the value of second number into variable num2 and the value
of third number into variable num3
Step 4 : If the condition num1 is larger than num2
Step 4.1: Then if num1 is larger than num3
Step 4.1.1: Print num1 is the largest of three
numbers
Step 4.2: Otherwise
Step 4.2.1: Print num3 is the largest of three
numbers
Algorithm - Largest of 3 numbers

35. Step 5: Otherwise
Step 5.1 : If num2 is larger than num3
Step 5.1.1: Print num2 is the largest of three
numbers
Step 6 : Otherwise
Step 6.1 : Print num3 is the largest of three
numbers
Step 7 : Stop

36. Flowchart - largest of three numbers

37. Program to find the largest of three numbers
#include <stdio.h>
int main()
{
int num1, num2, num3;
printf("Enter three numbers");
scanf("%d,%d,%d",&num1,&num2,&num3);
if(num1>num2)
if(num1>num3)
printf("%d is the largest of the three",num1);
else
printf("%d is the largest of the three",num3);
else
if(num2>num3)
printf("%d is the largest of the three",num2);
else
printf("%d is the largest of the three",num3);
return 0;
}

38. Some Other Forms of Nested - if
if (expression1)
{
if (expression2)
statement 1;
else
{
statement 2;
}
}
Else clause is associated with the closest preceding
unmatched if
if (expression1)
{
if (expression2)
statement 1;
}
else
{
statement 2;
}

39. Summary

40. 1. Schaum Series, Gottfried B. S., Tata McGraw Hill,
Programming with C
2. Brian W. Kernighan and Dennis M. Ritchie, Pearson,
C Programming Language
REFERENCES

41. THANK YOU