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help!
what is the program of a simple c++ program of identifying if the number entered is prime or not using while loop.. is it possible to program without using bool??

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The original request asked for a simple prime test using a while loop and "without using bool." Several replies posted a working but nonstandard brute-force solution (notably ) and commenters like and rightly pointed out the old Borland-style headers and style problems. Below is a modern, compact, standard‑conforming example that uses only while loops and an int flag (1 = prime, 0 = composite). It avoids counting all divisors and exits as soon as a divisor is found.

#include <iostream>

int main()
{
    unsigned long long n;
    std::cout << "Enter a positive integer: ";
    if (!(std::cin >> n)) return 0;

    if (n < 2) { std::cout << n << " is not prime\n"; return 0; }
    if (n == 2) { std::cout << n << " is prime\n"; return 0; }
    if (n % 2 == 0) { std::cout << n << " is not prime\n"; return 0; }

    unsigned long long i = 3;
    int isPrime = 1; // no bool used
    while (i <= n / i) // safe alternative to i*i <= n
    {
        if (n % i == 0) { isPrime = 0; break; }
        i += 2; // skip even divisors
    }

    if (isPrime) std::cout << n << " is prime\n";
    else         std::cout << n << " is not prime\n";
    return 0;
}

Notes and cautions: the inner test is O(sqrt(n)) and far faster than counting all divisors; i <= n / i avoids floating point and potential overflow. For many numbers, use a sieve; for very large single numbers, use a probabilistic or deterministic Miller–Rabin implementation. Avoid obsolete compilers/headers such as Turbo C++ or conio.h; compile with a modern compiler (g++/clang++) and a current language standard.

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Member Avatar for WaltP

what is the program of a simple c++ program of identifying if the number entered is prime or not using while loop..

It's a Prime Number Test Program.

is it possible to program without using bool??

yes.

Member Avatar for mrSatellite

can anyone show me the code of prime number program using while loop but without using bool..?

Member Avatar for pseudorandom21

can anyone show me the code of prime number program using while loop but without using bool..?

Can you use google, or do it yourself?

Member Avatar for mrSatellite

i dont know how, thats why i'm asking for help.. and i cant find any prime number program in google that uses while loop but doesnt use bool.

Edited by mrSatellite because: n/a
Member Avatar for Member #897610

ok

Edited by Member #897610 because: n/a
Member Avatar for Member #897610 
//enter the given rang from keyboard
//u will get prime no from given range
//13-11-20103
//prime_rng.cpp



#include<iostream.h>
#include<conio.h>
int main()
{
clrscr();
int st_no,end_no,div,no_div=0;
cout<<"Enter the starting no ";
cin>>st_no ;
cout<<"Enter the enging no ";
cin>>end_no ;

        while(st_no<=end_no)
        {  div=st_no;
            no_div=0;

            while(div>=1)
            {
                if(st_no%div==0)
                {
                no_div= no_div+ 1   ;
                }
                div--;
            }

if(no_div<=2)
{
cout<<st_no<< "  IS  PRIME"<<endl<<endl;
}
st_no++;

            }
return 0;
}
Edited by deceptikon because: Added code tags, removed personal information
commented: Do NOT do homework for others. YOU dont get the grade! -4
Member Avatar for pseudorandom21

i dont know how, thats why i'm asking for help.. and i cant find any prime number program in google that uses while loop but doesnt use bool.

Well anything we would write for you would be using modern, standard C++ instead of your 30 year old outdated non-standard C++ that you compile with Borland Turbo C++. So you can see the problem with us writing a program for you every time you're too lazy to use a search engine to learn something.

Yeah, and in place of the bool use an integer, use the value "0" for false and "1" for true. Enjoy your wasted programming "skills".

commented: wtf +0
Member Avatar for WaltP 
//enter the given rang from keyboard
//u will get prime no from given range
//safwan hashmi
//email was here
//13-11-20103
//prime_rng.cpp
...

Very bad code:
1) terrible formatting - inconsistent
2) using code that at least 15 years old
3) using headers that ate at least 10 years old and have been replaced
4) using functions that no compiler uses to this day
5) Massaging your ego and giving out code that allows the OP to cheat

Good Job!

And thank you for posting your email address so web-bots can harvest it and add you to thousands of SPAM lists.

commented: Point well made +8
commented: stupid +0
Member Avatar for Member #897610

i m studnt . i learn progrmming from start, "means" from simple C.first i learned basic things of programming .
if u people dose not like this post . plz rmve me from daniWeb .i will learn programming to other c++ webssite .
thnkx

Member Avatar for creative_m

num 2 and 3 are primes
if num mod 6 = 1 or num mod 6 = 5
it is possible to be a prime.
or the number is a result of ( prime num * another prime num )
otherwise it is not a prime number.
i hope this will help you.

Member Avatar for mrSatellite

thnk you (pseudo) for your comments.. i didnt know people here are rude..
hope you *** due to your EXCELLENT programming SKILLS!

Member Avatar for pseudorandom21

thnk you (pseudo) for your comments.. i didnt know people here are rude..
hope you *** due to your EXCELLENT programming SKILLS!

I'm quite happy you feel as such. But isn't that a threat? :( Daniweb likely frowns upon threatening other members.

I'm sorry I called your programming "skills" wasted, I'm sure they're quite useful to you and your people. But for most of the rest of the world, we require "ISO/IEC C++ 2003".

Please see http://en.wikipedia.org/wiki/C%2B%2B
for information regarding future revisions to the C++ standard.

Edited by pseudorandom21 because: n/a
Member Avatar for Member #897610

Very bad code:
1) terrible formatting - inconsistent
2) using code that at least 15 years old
3) using headers that ate at least 10 years old and have been replaced
4) using functions that no compiler uses to this day
5) Massaging your ego and giving out code that allows the OP to cheat

Good Job!

**And thank you for posting your email address so web-bots can harvest it and add you to thousands of SPAM lists.
people on Daniweb total disapoint and degrade student..How cheap :( that y many aur class flow lve Daniweb including me .and they Join other forums they learn better **

Edited by Member #897610
Member Avatar for delta_frost

Well testing for primes can be a very bad job when you deal with a mathematical problem involving very big numbers.The test for prime for a number x should be carried up to less than equal to sqrt(x). //I came across a program to find the sum of all primes below 2 million.I ran my code without considering sqrt and it took more than some 5 minutes on my i7 2nd Gen.And yes another category for testing primes is that all of them are of the form 30k + i where k is any whole number and i belongs to {3,7,11,13,1719,23,29}

Edited by delta_frost
Member Avatar for amaya ali

can anyone show me the code of prime number program using d0-while loop but without using Turboo C++..?

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