repeting program from function main

[mishrashubham]

I am learning c++ since 6months, so I am an extreme beginner. So please bear with me if I am making a stupid and obvious question here.
Also I would like to say that I have studied loops but not arrays and pointers etc. So if the answer is out of my bounds, please convey that to me.
Thank you.
So, now to my question.
I have written this program here which calculates the lowest(other than 1) and highest(other than the number itself) factors of a given number.The program asks for a number larger than 1. What I want the program to do is if the user inputs a number smaller than 1 then it will run again saying that what the user has entered is wrong value. I have used the following method

[code]
//Calculating the highest and lowest factors of a given number in this program
//Also repeating the program from starting point if value input does not satisfy condition
//that is specified

#include<iostream.h>
int calculate()
{
int num, factors, factorl;
char response;
do{
cout<<"Enter a number larger than 1"<<endl;
cin>>num;
if (num>1)
{
factors=2;
factorl=num-1;
while(num%factors>0)factors++;
while(num%factorl>0)factorl--;
cout<<"The smallest factor of "<<num<<" is equal to "<<factors<<endl;
cout<<"The largest factor of "<<num<<" is equal to "<<factorl<<endl<<endl<<endl;
}
else
{
cout<<"Invalid input"<<endl;
calculate();}
cout<<"Do you want to calculate the smallest and largest factors again (y/n)"<<endl;
cin>>response;
}while(response=='y'||response=='Y');
return 0;
}
int main()
{
{
calculate();
}
return 0;
}
[code]


Is there any better way to do this.
Also is there a way to prevent the user from entering any character and asking him to enter again, in the same way as above?
Please help
Thank you

[PanGalactic]

First, please edit your post and put [code] tags around your code. That will make it easier for others to read.

mishrashubham wrote:

is there a way to prevent the user from entering any character and asking him to enter again, in the same way as above?

The first recommendation I have here is to split the calculate() function into two functions: one that does user input and one that calculates the factors.