Module 2 - Control Structures c programming.pptm.pdf

PRPEARED BY: PROF. NEHA HARDE ©
C PROGRAMMING
Module 2
Control Structures
Course Outcome (CO2):
Demonstrate the use of control structures.

WHAT IS CONTROL STRUCTURE ?
 A statement that is used to control the flow of execution in a program is
called control structure
 It combines instruction into logical unit
 Logical unit has one entry point and one exit point
There are three types of control structures available in C:
1) Sequence structure (straight line paths)
2) Selection structure (one or many branches)
3)Loop structure (repetition of a set of activities)

SEQUENCE STRUCTURE
In Sequence structure instructions are executed in the order they are written following the sequential flow

SELECTION STRCTURE
 Selection structures are used to perform
‘decision making‘ and then branch the program
flow based on the outcome of decision making
 It selects a statement to execute on the basis of
condition
 Statement is executed when the condition is true
and ignored when it is false

LOOP STRUCTURE
 A loop structure is used to execute a certain set
of actions for a predefined number of times or
until a particular condition is satisfied

 If statement
 If else statement
 Nested if else
 Else if ladder
 Switch Case Statement
 If else vs switch case
Decision Control Structures

IF STATEMENT
 if statement is used to check a given condition and perform
operations depending upon the correctness of that condition
 It is mostly used in the scenario where we need to perform
the different operations for the different conditions
Syntax:
if(expression)
{
//code to be executed
}

IF STATEMENT
#include<stdio.h>
int main()
{
int n;
printf("Enter a number:");
scanf("%d", &n);
if(n%2 == 0)
{
printf("%d is even number“ ,n);
}
return 0;
}
Example: Find whether the
given number is even number

IF ELSE STATEMENT
 The if-else statement is used to perform two operations
for a single condition
i.e., one is for the correctness of the condition, and the
other is for the incorrectness of the condition
 if and else block cannot be executed simultaneously

IF ELSE STATEMENT
Syntax:
if(expression)
{
//code to be executed if condition is true
}
else
{
//code to be executed if condition is false
}
int main()
{
int n;
printf("Enter a number:");
scanf("%d", &n);
if(n%2 == 0)
{
printf("%d is even
number“ ,n);
}
else
{
printf("%d is odd
number“ ,n);
}
return 0;
}
Example: Find whether the given number is
even number or odd number

NESTED IF ELSE STATEMENT
 When an if else statement is present
inside the body of another “if” or
“else” then this is called nested if else
 It is used when there are more than one
condition to check at a time

NESTED IF ELSE STATEMENT
Syntax:
if(condition)
{
if(condition2)
{
//Statements inside the body of nested "if"
}
else
{
//Statements inside the body of nested "else"
}
}
else
{
//Statements inside the body of "else"
}

NESTED IF ELSE
STATEMENT
#include<stdio.h>
int main()
{
int age;
char gender;
printf("n Your gender ? (M/F)");
scanf("%c", &gender);
printf("n Enter your age:");
scanf("%d", &age);
if(gender == 'M')
{
if(age >= 21)
printf("n Eligible for marriage");
else
printf("n Not eligible for Marriage");
}
Example: Find whether the person is eligible for marriage or not based on the age and gender
else
{
if(age>= 18)
printf("n Eligible for
marriage");
else
printf("n Not eligible for
Marriage");
}
return 0;
}

ELSE IF LADDER
 The if-else-if ladder statement is an extension
to the if-else statement
 In if-else-if ladder statement, if a condition is
true then the statements defined in the if
block will be executed, otherwise if some
other condition is true then the statements
defined in the else-if block will be executed,
at the last if none of the condition is true then
the statements defined in the else block will
be executed

ELSE IF LADDER
Syntax:
if(condition1)
{
//code to be executed if condition1 is true
}
else if(condition2)
{
}
else if(condition3)
{
}
else
{
//code to be executed if all the conditions are false
}

NESTED IF ELSE
STATEMENT
#include<stdio.h>
int main()
{
int age;
printf("n Enter your age:");
scanf("%d", &age);
if(age >= 60)
printf("n Vaccination will start from 1st
Feb 2021");
else if(age >= 45)
March 2021 ");
else if(age >= 18)
May 2021 ");
else
printf("n Not eligible for Vaccination");
return 0;
}
Example: Find start date of vaccination based on the age of the person

SWITCH CASE
STATEMENT
 The switch statement in C is an alternate to if-else-if
ladder statement which allows us to execute multiple
operations for the different possible values of a single
variable called switch variable
 Switch statement in C tests the value of a variable and
compares it with multiple cases
 Once the case match is found, a block of statements
associated with that particular case is executed
 If a case match is NOT found, then the default
statement is executed, and the control goes out of the
switch block
Syntax:
switch (expression)

{
case constant1:
// statements
break;
case constant2:
// statements
break;
.
.
.
default:
// default statements
}

SWITCH CASE
STATEMENT
Rules for Switch Statement:
 The switch expression must be of an integer or character type
 The case value must be an integer or character constant
 The case value can be used only inside the switch statement
 The break statement in switch case is not must.
 If there is no break statement found in the case, all the cases
will be executed present after the matched case (fall through
the state of C switch statement)

SWITCH CASE
STATEMENT
#include<stdio.h>
#include<stdlib.h>
int main()
{
int ch, n1, n2;
printf("n MENU n 1. addition n 2. subtraction");
printf(" n 3. multiplication n 4. division");
printf(" n 5. modulus n 6. exit n Enter you choice:");
scanf("%d", &ch);
printf("n Enter two numbers:");
scanf("%d %d", &n1, &n2);
switch(ch)
{
case 1:
printf("n addition = %d", n1+n2);
break;
case 2:
printf("n subtraction = %d", n1-
n2);
break;
case 3:
printf("n multiplication = %d", n1*n2);
break;
case 4:
printf("n division = %d", n1/n2);
break;
case 5:
printf("n remainder = %d", n1%n2);
break;
case 6:
exit(0);
default:
printf("n You have entered wrong
choice!!");
break;
}
return 0;
}
Example: Write a C Program to perform addition, subtraction, multiplication, division and modulus operations using switch case.

IF ELSE VS SWITCH CASE

 Looping structure
 for loop
 do while loop
 while loop
 break statement
 continue statement
Loop Control Structures

LOOPING STRUCTURE

FOR LOOP
For loop specifies the three things:
 Setting a loop counter to an initial value
 Testing a loop counter to determine whether its value has reached the number of repetitions required
 Increasing the value of loop counter each time the program within the loop has been executed
Syntax:
for(initialization expr; test expr; update expr)
{
// body of the loop
// statements we want to execute
}

FOR LOOP
Flowchart of For loop

FOR LOOP
#include<stdio.h>
int main()
{
int i;
for(i=1; i<=10; i++)
printf(“%d”, i);
return 0;
}
Example: Print 1 to 10 numbers using for loop

WHILE LOOP
 While loop is also known as a pre-tested loop
 It can be viewed as a repeating if statement
 The while loop is mostly used in the case where the number of iterations is not known in advance
Syntax:
initialization expression;
while (test_expression)
{
// statements
update_expression;
}

WHILE LOOP
Flowchart of while loop

WHILE LOOP
#include<stdio.h>
int main()
{
int i = 1;
while(i <= 10)
{
i++;
}
return 0;
}
Example: Print 1 to 10 numbers using while loop

DO WHILE LOOP
 A do...while loop is similar to the while loop except that the condition is always executed after the
body of a loop so it is an exit-controlled loop
 The do-while loop is mainly used in the case where we need to execute the loop at least once
 The do-while loop is mostly used in menu-driven programs where the termination condition depends
upon the end user
Syntax:
initialization expression;
do
{
// statements
update_expression;
} while (test_expression);

DO WHILE LOOP
Flowchart of do-while loop

WHILE LOOP
#include<stdio.h>
int main()
{
int i = 1;
do
{
i++;
} while(i <= 10);
return 0;
}
Example: Print 1 to 10 numbers using do - while loop

BREAK STATEMENT
 The break is a keyword in C which is used to bring the program control out of the loop
 The break statement is used inside loops or switch statement and it is associated with if
Syntax:
//loop or switch case
break;

#include<stdio.h>
int main()
{
int n, count = 0, sum=0;
printf(“n Get sum of any 5 numbers between 1 to 10”);
do
{
printf(“n Enter a number only between 1 to 10”);
scanf(“%d”, &n);
if(n < 1 && n > 10)
break;
sum = sum + n;
count++;
}while(count <= 5);
return 0;
}
Example: Find sum of any 5 numbers entered only between 1 to 10
BREAK STATEMENT

CONTINUE
STATEMENT
 The continue statement skips the current iteration of the loop and continues with the next iteration
 When the continue statement is executed in the loop, the code inside the loop following the
continue statement will be skipped and next iteration of the loop will begin.
Syntax:
//loop or switch case
continue;

#include<stdio.h>
int main()
{
int i;
for(i=1; i<=10; i++)
{
if(i == 4)
continue;
}
return 0;
}
Example: Print 1 to 10 numbers except 4 using for loop
CONTINUE
STATEMENT

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