C Prog. - Decision & Loop Controls

C Programming - Decision & Loop
Control

Organized By: Vinay Arora
Assistant Professor, CSED
Thapar University, Patiala

Decision Control

The if statement

The if-else statement

The conditional operators

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Forms of if

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Forms of if (contd.)

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Relational Operator

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Demonstrating - If

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Flowchart

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Expression in Conditional Part

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Multiple statements within if

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Demonstrating If - Else

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Flowchart If-Else

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Logical Operators with If-Else

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Else-if ladder

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Smallest amongst 3 nos.

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Program using Logical OR, elseif

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Calculate Salary as per following table

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&& - Logical AND
C allows usage of three logical operators, namely, &&, || and !

These are to be read as ‘AND’ ‘OR’ and ‘NOT’ respectively.

Don’t use the single symbol | and &. These single symbols also have a
meaning.

The first two operators, && and ||, allow two or more conditions to be
combined in an if statement.

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&& - Logical AND (C Program)

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| | - Logical OR (C Program)

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! - Logical NOT
This operator reverses the result of the expression it operates on.

For example, if the expression evaluates to a non-zero value, then
applying ! operator to it results into a 0.

Vice versa, if the expression evaluates to zero then on applying !
operator to it makes it 1, a non-zero value.

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! - Logical NOT (C Program)

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&&, ||, ! Operator

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? : - Conditional Operator
The conditional operators ? and : are sometimes called Ternary
Operators since they take three arguments.

They form a kind of foreshortened if-then-else.

Their general form is, expression 1 ? expression 2 : expression 3

If expression 1 is true (that is, if its value is non-zero), then the value
returned will be expression 2, otherwise the value returned will be
expression 3.

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Conditional Operator (C Program)

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goto Statement

goto is used to switch the control flow.

In a difficult programming situation it seems so easy to use a goto to
take the control.

In most of the scenarios use of goto is depreciated.

goto can be replaced by if-else, switch, for.

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goto Statement - Program

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switch Statement
The control statement that allows us to make a decision from the number
of choices is called a switch.

The integer expression following the keyword switch is any C expression that
will yield an integer value.

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switch Statement - Flowchart

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switch Statement - Program

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Loops
Repetitive instructions is done through a Loop control instruction.

This involves repeating some portion of the program either a
specified number of times or until a particular condition is being
satisfied.

There are three methods by way of which we can repeat a part of a
program. They are:

(a) Using a while statement
(b) Using a do-while statement
(c) Using a for statement

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while Loop - Flowchart

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while Loop – general form

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while Loop – forms of conditions

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while Loop – C Program

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While Loop – Program 1
//Program to demonstrate simple while loop
#include<stdio.h>
#include<conio.h>

void main()
{
int i=1;
clrscr();

while (i<=10)
{
printf("%dn",i);
i=i+1;
}
getch();
}

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Output

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//Program to demonstrate simple while loop with decrement operator
#include<stdio.h>
#include<conio.h>

void main()
{
int i=5;
clrscr();

while (i>=1)
{
printf("%dn",i);
i=i-1;
}
getch();
}

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CSED

/* Program to demonstrate simple while loop taking incremental value
as float */
#include<stdio.h>
#include<conio.h>

void main()
{
float i=10.0;
clrscr();

while (i<=10.5)
{
printf("nCivil Engineering at Thapar");
i=i+.1;
}
getch();
}
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//Demonstrating simple while loop with integer value out of range
#include<stdio.h>
#include<conio.h>

void main()
{
int i=1;
clrscr();

while (i<=32767)
{
printf("%dn",i);
i=i+1;
}
getch();
}

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Output – Infinite Loop

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//Program to demonstrate simple while loop
#include<stdio.h>
#include<conio.h>

void main()
{
int i=1;
clrscr();

while (i<=10);
{
printf("%dn",i);
i=i+1;
}
getch();
}

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CSED

//Program to demonstrate post increment operator in while loop
#include<stdio.h>
#include<conio.h>

void main()
{
int i=1;
clrscr();

while (i<=10)
{
printf("%dn",i);
i=i++;
}
getch();
}

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CSED

//Program to demonstrate compound assignment operator within while loop
#include<stdio.h>
#include<conio.h>

void main()
{
int i=1;
clrscr();

while (i<=5)
{
printf("%dn",i);
i+=1;
}
getch();
}

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CSED

//Program to demonstrate post increment operator with while loop
#include<stdio.h>
#include<conio.h>

void main()
{
int i=0;
clrscr();

while (i++ < 5)
{
printf("%dn",i);

}
getch();
}

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CSED

//Program to find out even numbers between 1-10
#include<stdio.h>
#include<conio.h>

void main()
{
int i=1;
clrscr();

while (i<=10)
{
if (i%2==0)
printf("%dn",i);
i=i+1;
}
getch();
}
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Do-while Loop

While

Do while

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Do-while Loop – Program 10
//Program to demonstrate DO-WHILE loop
#include<stdio.h>
#include<conio.h>

void main()
{
int i=1;
clrscr();

/*
while(i<1)
{
printf("hello i am at Thapar");
}
*/

do
{
printf("hello i am at Thapar");
}
while(i<1);

getch();
}

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Program Transformation

Unary Post Increment
Operator

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Program Transformation

Compound
Assignment Operator

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For Loop
The for allows us to specify three things about a loop in a single line:

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For Loop (Program-1)
//Program to demonstrate simple For loop
#include<stdio.h>
#include<conio.h>

void main()
{
int i;
clrscr();

for (i=1; i<=10; i=i+1)
printf("%dn",i);

getch();
}

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For Loop (Program-1 Output)

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CSED

#include<stdio.h>
#include<conio.h>

void main()
{
int i;
clrscr();

for (i=1; i<=10;)
{
printf("%dn",i);
i=i+1;
}
getch();
}

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CSED


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//Print numbers from 1 to 5
#include<stdio.h>
#include<conio.h>

void main()
{
int i=1;
clrscr();

for (;i<=5;i=i+1)
{
printf("%dn",i);
}
getch();
}

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#include<stdio.h>
#include<conio.h>

void main()
{
int i=1;
clrscr();

for (;i<=5;)
{
printf("%dn",i);
i=i+1;
}
getch();
}

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CSED


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CSED

#include<stdio.h>
#include<conio.h>

void main()
{
int i;
clrscr();

for (i=0;i++<5;)
{
printf("%dn",i);
}
getch();
}

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CSED


Vinay Arora
CSED

#include<stdio.h>
#include<conio.h>

void main()
{
int i;
clrscr();

for (i=0;++i<5;)
{
printf("%dn",i);
}
getch();
}

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CSED


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CSED

//Program to demonstrate NESTED For loop
#include<stdio.h>
#include<conio.h>

void main()
{
int i,j;
clrscr();

for (i=1;i<=5;i=i+1)
{
printf("n");
for (j=1;j<=i;j=j+1)
{
printf(" *");
}
}
getch();
}
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CSED


Vinay Arora
CSED

Thnx…

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CSED

C Prog. - Decision & Loop Controls

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