Program to calculate sum of series using for loop in C.

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/*Program to calculate sum of series

 1/1!+1/2!+1/3!+.......+1/n!

 where n is the value entered by user.

 =>Explicit type conversion
 =>Nested loop
*/

#include<stdio.h>
#include<conio.h>
void main()
{
int i,n,j;
float sum,mul;
clrscr();
sum=0;


printf("\nEnter limit number : ");
scanf("%d",&n);


printf("\nSeries=");

printf("\n---------------------\n");

for(i=1;i<=n;i++)
{

mul=1;
printf(" +1/%d! ",i);

for(j=1;j<=i;j++)
{
mul=mul*j; //factorial
}

sum=sum+(float)1/mul;  //Explicit type conversion
}

printf("\n---------------------\n");

printf("\nSum of series= %.3f",sum);

getch();
}

Program to check input number is perfect number or not using for loop in C.

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/*Program to check input number is perfect number or not*/

/*Perfect number: sum of all it's factors is equal to number itself */

#include<stdio.h>
#include<conio.h>
void main()
{
int num,i,sum;
clrscr();
sum=0;

printf("\nEnter any number:");
scanf("%d",&num);

clrscr();  //for clear screen

printf("\n-------------------------------");
printf("\nNumber entered is: %d",num);
printf("\n-------------------------------");
printf("\nFactores of %d is:",num);
printf("\n-----------------------------\n");

for(i=1;i<num;i++)
{

if(num%i==0)
{
printf(" %d ",i);
sum=sum+i;
}

}

printf("\nSum of factors is: %d",sum);

if(num==sum)
{
printf("\n%d is a perfect number",num);
}
else
{
printf("\n%d is not a perfect number",num);
}

printf("\n------------------------------");

getch();
}

Program to check input number is perfect number or not using do while loop in C.

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/*Program to check input number is perfect number or not*/

/*Perfect number: sum of all it's factors is equal to number itself */

#include<stdio.h>
#include<conio.h>
void main()
{
int num,i,sum;
clrscr();
sum=0;
i=1;

printf("\nEnter any number:");
scanf("%d",&num);

clrscr();  //for clear screen

printf("\n-------------------------------");
printf("\nNumber entered is: %d",num);
printf("\n-------------------------------");
printf("\nFactores of %d is:",num);
printf("\n-----------------------------\n");

do
{

if(num%i==0)
{
printf(" %d ",i);
sum=sum+i;
}

i++;
}while(i<num);

printf("\nSum of factors is: %d",sum);

if(num==sum)
{
printf("\n%d is a perfect number",num);
}
else
{
printf("\n%d is not a perfect number",num);
}

printf("\n------------------------------");

getch();
}

Program to find factor of any number in C.

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/* Program to find factor of any number */

#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();

int num,i;
printf("\n---------Factor Finder--------");
printf("\nEnter a number:");
scanf("%d",&num);

printf("\nFactors of %d are : ",num);
for(i=1;i<num;i++)
{
if(num%i==0)
{
printf("  %d",i);
}

}

getch();
}