The While Loop
The while loop is an entry
controlled loop statement, means the condition is evaluated first and it is
true, then the body of the loop is executed. After executing the body of the
loop, the condition is once again evaluated and if it is true, the body is executed
once again, the process of repeated execution of the body of the loop continues
until the condition finally becomes false and the control is transferred out of
the loop.
Example : Program to give
maximum and minimum value of character datatype.
/* Program gives maximum
and minimum value of character datatype */
#include<stdio.h>
#include<conio.h>
void main()
{
char i,j
; /* Local definitions */
/* Statements
*/
clrscr();
i = 1;
while
(i > 0)
{
j = i;
i++;
} /* while */
printf ("The maximum
value of char is n",j);
printf ("The value
of char after overflow is n",i);
getch();
} /* main */
Output:
The maximum value of char
is 127
The value of char
after overflow is -128
Do-While Loop
It is also repetitive
control structure and executes the body of the loop once irrespective of the
condition, then it checks the condition and continues the execution until the
condition becomes false.
The statements with
in the body of the loop is executed once, then it evaluates for the condition,
if it is true, then it executes body until the condition becomes false.
Example : Program to print
n numbers using do..while loop.
/* Program to print n
numbers */
#include<stdio.h>
#include<conio.h>
void main()
{
int
i,n; /* Local definitions */
/* Statements */
clrscr();
printf("Enter the
number : ");
scanf("%d",&n);
i = 0;
do
{
printf("the numbers are %d \n",i);
i = i +1;
} /* do..while */
while( i<n) ;
getch();
} /* main */
Output:
Enter the number : 6
the numbers are 0
the numbers are 1
the numbers are 2
the numbers are 3
the numbers are 4
the numbers are 5
The for loop:
The for loop is another
repetitive control structure, and is used to execute set of instructions
repeatedly until the condition becomes false.
The assignment,
incrementation or decrementation and condition checking is done in for
statement only, where as other control structures are not offered all these
features in one statement.
Example : Program to print
n numbers using for..loop structure.
/* Program to print n
numbers */
#include<stdio.h>
#include<conio.h>
void main()
{
int i,n; /* Local
definitions */
/* Statements */
clrscr();
printf("Enter a
number :");
scanf("%d",&n);
for(i = 0; i<n; i= i+1)
{
printf("The numbers are %d \n",i);
} /* for */
getch();
}/* main */
Output:
Enter a number :5
The numbers are 0
The numbers are 1
The numbers are 2
The numbers are 3
The numbers are 4
Nesting of For loop
Like if statement for loop
also nested. The loop within the loop is called nested loop. In nested for
loops two or more for statements are included in the body of the loop. The
number of iterations in this type of structure will be equal to the number of iterations
in the outer loop multiplied by the number of iterations in the inner loop.
Example : Program to
demonstrate nesting of for loops.
/* Program using nesting
of for loops */
#include<stdio.h>
main()
{
int
i,j; /* Local definitions */
/*
Statements */
for(i=1;i<=3;i++)
{ /* for loop starting */
printf("\n");
for(j=1;j<=3;j++)
printf("%d\t",j);
} /* for */
}
/* main */
Output
1
2 3
1
2 3
1
2 3
The Switch Statement
The switch statement is
used to pickup or execute a particular group of statements from several
available group of statements. It allows us to make a decision from the number
of choices.
It is a multiway decision
statement, it tests the value of given variable or expression against a list of
case values and when a match is found, a block of statements associated with
that case is executed.
Example : Program to
print the given number is odd/even using switch case statement.
/* Prints the given number
is odd/even */
#include<stdio.h>
#include<conio.h>
void main()
{
int
i,n; /* Local definitions */
/* Statements */
clrscr();
printf("Enter a Number : ");
scanf("%d",&n);
for(i = 1; i<=n; i= i+1)
{
switch(i%2)
{
case 0 :
printf("The number %d is even \n",i);
break;
case 1 :
printf("The number %d
is odd \n",i);
break;
} /* switch case */
} /* for */
getch();
}
/* main */
Output:
Enter a Number : 7
The number 1 is odd
The number 2 is even
The number 3 is odd
The number 4 is even
The number 5 is odd
The number 6 is even
The number 7 is odd
Nested Switch() Case
'C' supports the nested
switch( ) statements. The inner switch( ) statement can be a part of an outer
switch( ) statement. The inner and outer switch( ) case constants may be same.
No conflict arises even if they are same.
Example : Program to find
even or odd numbers using nested switch() case.
/* Program to find even or
odd numbers using nested switch() case */
#include<stdio.h>
#include<conio.h>
void main()
{
/* Local definitions */
int a,b;
/* Statements */
clrscr();
printf("Enter a
number:");
scanf("%d",&a);
switch(a)
{ /* switch case1 open */
case 0:
printf("The number is even.\n");
break;
case 1:
printf("The number is odd.\n");
break;
default:
b=a%2;
switch(b)
{
/* Switch case2 open */
case 0:
printf("The number is even.\n");
break;
default:
printf("The number is odd.\n");
}
/* Switch2 */
}
/* Switch1 */
getch();
}
/* main */
Output: 1
Enter a number:89
The number is odd.
Output: 2
Enter a number:48
The number is even.
The Break Statement
The break statement is
used to terminate the loop. When the keyword break is used inside any
'C' loop, control automatically transferred to the first statement after the
loop. A break is usually associated with an if statement.
Example
: Program to print the number upto 5 using break statement.
/* Program using break
statement */
#include<stdio.h>
#include<conio.h>
main ()
{
/* Local definitions
*/
int i;
/* Statements */
for(i=1;i<=10;i++)
{
if(i==6)
break; /* break statement */
printf("%d", i);
} /* for */
} /*
main */
Output
1 2 3 4 5
The Continue Statement
In some situations, we
want to take the control to the beginning of the loop, bypassing the statements
inside the loop which have not yet been executed, for this purpose the continue
is used. When the statement continue is encountered inside any 'C' loop control
automatically passes to the beginning of the loop.
Example : Calculate
the sum of the given positive numbers.
/* Program to calculate
the sum of the given positive numbers */
#include<stdio.h>
main
{
int i,n,sum=0; /* Local definitions */
/* Statements */
for(i=1;i<=5;i++)
{
printf("Enter any number.....\n");
scanf("%d",&n);
if(n<0)
continue;
else
sum=sum+n;
} /* for */
printf("Sum is
.....%d",sum);
}
/* main */
Output
Enter any number.....10
Enter any number.....5
Enter any number.....15
Enter any number.....25
Enter any number.....-10
Enter any number.....50
Sum is .....105
Goto Statement
'C' provides the goto
statement to transfer control unconditionally from one place to another place
in the program.
A goto statement can cause
program control almost anywhere in the program unconditionally.
The goto statement
requires a label to identify the place to move the execution. A label is a valid
variable name and must be ended with colon (:).
Example :
Program to prints the
given both number is equal or not.
/* Program using goto
statement */
#include<stdio.h>
#include<conio.h>
main ()
{
/* Local definitions */
int a, b;
/* Statements */
printf("\nEnter the numbers");
scanf("%d %d",&a,&b);
if(a==b)
goto equal;
else
{
printf("\n A and B are not equal");
exit(0);
} /* if else */
equal:
printf("A and B are
equal");
}
/* main */
Output :
1. Enter the numbers
3, 3
A and B are
equal
2. Enter the numbers
3, 4
A and B are
not equal
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