Logical error when 0 is input into loop

[Alenik1989]

ok i have this code that executes for all # between 0 and 1001 perfectly. it is a cod to find the factors of inputed data and then determine it as a perfect number or not, also it suppose to loop bach to data entry when user inputs an out of range number.
my problem is number 0 when i input 0 the program terminates while is suppose to loop bach up with an error.
does any body see the error? if yes can you tell me?TANX
here is my code...

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
int sum,sum1=0,sumt=0,num,root,dev,counter=0;
const int SENTINEL=-100;
 
cout<<"ENTER #<enter exit to exit> : ";   //constant and integers
while (num)                      //the loop that reruns the prog due an invalid entry                           
{
    cin>>num;                            //# entered by user
    counter++;
    if (num==SENTINEL)                   //a # to exit the prog
        break;
if (0<num && num<1001)                   //declaring the range
{     sum=0,sum1=0,sumt=0;
    root=pow(num,0.5);                   //second root of that #
    cout<<"devisors for input "<<counter<<" <#"<<num<<"> are: 1 "<<"  "<<num<<"   ";
 
    for (root;1<root;root--)             //the loop and conditions
{
        if(num%root==0)                                  
{
    dev=num/root;
    cout<<root<<"    "<<dev<<"     ";   //formula to calculate the sum of products
    sum=dev+root;
    sum1+=sum;
 
 
 
}
       else
    continue;      
 
}
    sumt=sum1+1;
    cout<<"SUM="<<sumt<<endl<<endl;          //determination for perfect number
    if(sumt==num)
        cout<<num<<" is a perfect Nmber"<<endl;
 
}
    else
    {
        cout<<"Input "<<counter<<" <#"<<num<<"> is an invalid number.Number must be between 1 and 1000. Please     enter another number.\n"<<endl;
continue;               //error for invalid entry and loop for back to data entry
    }
}
 
    return 0;
}

[rhitam30111985]

while (num) //the loop that reruns the prog due an invalid entry
{
cin>>num; //# entered by user
counter++;
if (num==SENTINEL) //a # to exit the prog
break;

}[/code]

num is 0... SENTINEL is -100... 0!=-100.. if condition is false ... hence ...rest of the program will be excecuted .. unless i am missing something ..

[amitpatel66]

ok i have this code that executes for all # between 0 and 1001 perfectly. it is a cod to find the factors of inputed data and then determine it as a perfect number or not, also it suppose to loop bach to data entry when user inputs an out of range number.
my problem is number 0 when i input 0 the program terminates while is suppose to loop bach up with an error.
does any body see the error? if yes can you tell me?TANX
here is my code...

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
int sum,sum1=0,sumt=0,num,root,dev,counter=0;
const int SENTINEL=-100;
 
cout<<"ENTER #<enter exit to exit> : ";   //constant and integers
while (num)                      //the loop that reruns the prog due an invalid entry                           
{
    cin>>num;                            //# entered by user
    counter++;
    if (num==SENTINEL)                   //a # to exit the prog
        break;
if (0<num && num<1001)                   //declaring the range
{     sum=0,sum1=0,sumt=0;
    root=pow(num,0.5);                   //second root of that #
    cout<<"devisors for input "<<counter<<" <#"<<num<<"> are: 1 "<<"  "<<num<<"   ";
 
    for (root;1<root;root--)             //the loop and conditions
{
        if(num%root==0)                                  
{
    dev=num/root;
    cout<<root<<"    "<<dev<<"     ";   //formula to calculate the sum of products
    sum=dev+root;
    sum1+=sum;
 
 
 
}
       else
    continue;      
 
}
    sumt=sum1+1;
    cout<<"SUM="<<sumt<<endl<<endl;          //determination for perfect number
    if(sumt==num)
        cout<<num<<" is a perfect Nmber"<<endl;
 
}
    else
    {
        cout<<"Input "<<counter<<" <#"<<num<<"> is an invalid number.Number must be between 1 and 1000. Please     enter another number.\n"<<endl;
continue;               //error for invalid entry and loop for back to data entry
    }
}
 
    return 0;
}

I think the program terminates because WHILE(0) returns false when num is passed as 0

[Alenik1989]

I think the program terminates because WHILE(0) returns false when num is passed as 0

Ok tanx. but why? 0 is like the other numbers ,isnt it?
what should i do about it?

[Alenik1989]

num is 0... SENTINEL is -100... 0!=-100.. if condition is false ... hence ...rest of the program will be excecuted .. unless i am missing something ..

yes u r right, but that is my problem
num=0 and SENTINEL=-100
so num!=-100
and the rest should be executed.
and it gives the right error ((( 0is an invalid number.Number must be between 1 and 1000. Please enter another number)). then in terminates the WHILE(num) and the program!!!!?

[sicarie]

Ok tanx. but why? 0 is like the other numbers ,isnt it?

A while loop has a true/false condition to see if it should keep looping. Most (if not all) C/C++ compilers will implement 0 as false and any other number as true (including negative numbers).

what should i do about it?

Not pass it 0 until you want it to exit.

[Alenik1989]

A while loop has a true/false condition to see if it should keep looping. Most (if not all) C/C++ compilers will implement 0 as false and any other number as true (including negative numbers).

TANX very much now at least i know why 0 is not working!!!!!

Not pass it 0 until you want it to exit.

i think thats what i'll do. i guess there is nothing else i can do right?
THANK YOU