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Q. Write a c program to check given number is perfect number or not. (C lan)
#include<stdio.h>
#include<conio.h>
int main()
{
int n,i=1,sum=0;
clrscr();
printf("Enter a number:");
scanf("%d",&n);
while(i<n)
{
if(n%i==0)
{
sum=sum+i;
}
i++;
}
if(sum==n)
printf("%d is a perfect number",i);
else
printf("%d is not a perfect number",i);
getch();
}
Out put
Enter number :6
6 is a perfect number
Another example
#include<stdio.h>
#include<conio.h>
int main()
{
int n,i=1,sum=0;
clrscr();
printf("Enter a number:");
scanf("%d",&n);
while(i<n)
{
if(n%i==0)
{
sum=sum+i;
}
i++;
}
if(sum==n)
printf("%d is a perfect number",i);
else
printf("%d is not a perfect number",i);
getch();
}
This C program checks whether an input number is a perfect number. A perfect number is a number that is equal to the sum of its proper divisors (excluding the number itself). For example, 6 is a perfect number because its divisors (1, 2, 3) sum to 6.
Breakdown of Code and Functions
1. “#include<stdio.h>“
- This is a preprocessor directive that includes the Standard Input Output header file. This file is required for using input/output functions like ‘
printf‘ and ‘scanf‘.
2. “int main()“
- This is the main function from where the execution of the program starts.
- The function returns an integer value (‘
0‘ by default) which indicates that the program has terminated successfully.
Variable Declarations:
int n, i = 1, sum = 0;
- ‘
n‘: Stores the number entered by the user. - ‘
i‘: Acts as a loop counter, initialized to 1. It will be used to check for divisors. - ‘
sum‘: Stores the sum of the divisors of the number. It is initialized to 0.
User Input:
printf("Enter a number: ");
scanf("%d", &n);
- ‘
printf("Enter a number: ")‘: Displays a message asking the user to enter a number. - ‘
scanf("%d", &n)': Takes an integer input from the user and stores it in the variable ‘n‘.
" while Loop "(Finding Divisors):
while(i <= n / 2) {
if(n % i == 0) {
sum = sum + i;
}
i++;
}
- ‘
while(i <= n / 2)‘: This loop runs until ‘i‘is less than or equal to ‘n / 2‘. This is because divisors of a number will always be less than or equal to half of that number. - ‘
if(n % i == 0)‘: This checks if ‘i‘ is a divisor of ‘n‘ by checking if the remainder of ‘n‘ divided by ‘i‘ is zero (i.e., ‘n % i == 0‘). - ‘
sum = sum + i‘: If ‘i‘ is a divisor, its value is added to the ‘sum‘ variable. - ‘
i++‘: Increment ‘i‘ to check the next number.
Check if the Number is Perfect:
if(sum == n) {
printf("%d is a perfect number\n", n);
} else {
printf("%d is not a perfect number\n", n);
}
- ‘
if(sum == n)‘: After the loop, the program checks if the sum of the divisors is equal to the number itself. - If true, it means the number is a perfect number and the program prints ‘
"n is a perfect number"‘. - Otherwise, it prints ‘
"n is not a perfect number"‘.
‘return 0;‘
- The ‘
return 0;‘ statement indicates that the program executed successfully and returns control back to the operating system.
Example of Program Execution:
Enter a number: 6
6 is a perfect number
Enter a number: 10
10 is not a perfect number
In this program:
- For the input ‘
6‘, the divisors of ‘6‘ are ‘1, 2, 3‘. The sum of these divisors is ‘1 + 2 + 3 = 6‘, so it correctly identifies ‘6‘ as a perfect number. - For the input ‘
10‘, the divisors are ‘1, 2, 5‘. The sum is ‘1 + 2 + 5 = 8‘, which is not equal to ‘10‘, so it identifies ‘10‘ as not a perfect number.
