The program is to find all the perfect numbers in the range, which starts from zero and ends at user defined limit. A perfect number is a one, whose sum of devisors is equals the number itself.

Logic: This is a slightly modified version of the previous program. Here, user need to enter the number as the upper limit for the for the iteration loop to find the perfect number The outer for loop traces the iteration till the limit,, wherein each of iteration inner for loop checks the present number is perfect or not, with the previous program’s logic. If it is, it prints out the present number.

In this program, the lower limit is constant zero. We can change that also, to make the program fully flexible, and to print out all the perfect number between the given range.

Program to find the perfect numbers below a given number.

#include<stdio.h>
#include<math.h>
void main()
{
int i,n,sum,lim;
clrscr();
printf(“nnt ENTER THE UPPER LIMIT…: “);
scanf(“%d”,&lim);
printf(“nnt THE PERFECT NUMBER ARE..:”);
for(n=1;n<lim;n++)
{
sum = 0;
for(i=1;i<n;i++)
if(n%i == 0)
sum = sum + i;
if (sum == n)
printf(“nnttt%d”,n);
}
getch();
}
Download exe and source code here.