Program to calculate sum of odd-even number series using while loop in C.

Code Box
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/*program to calculate sum of the series
1-2+3-4+5-6+7-8+9.......+n
odd-even number series(alternative)
where n is the limit entered by user.
*/

#include<stdio.h>
#include<conio.h>
void main()
{
int i,evensum,oddsum,sum,num;

clrscr();

evensum=0;
oddsum=0;

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

printf("\nOdd Number Series ");

printf("\nSeries= ");

i=1;                     //initialization

while(i<=num)
{

if(i%2==0)          // % modulus operator
{
printf(" - ");
evensum=evensum+i;
}
else
{
printf(" + ");
oddsum=oddsum+i;
}
printf("%d",i);

i++;                 //increment post fix operator

}

sum=oddsum-evensum;

printf("\n\nSum of series= %d",sum);

getch();
}