Prime numbers

[AndreasTm13]

I've got to display all of the prime numbers in the [a,b] interval,where a and b are introduced from the keyboard.

      int a,b,n,i,k=0,j;
    cout<<"a=";cin>>a;
    cout<<"b=";cin>>b;
    if(a<b)
    {
        for(i=a;i<=b;i++)
        {
            n=i;
            for(j=1;j<=n;j++)
                if(n%j==0)k++;
                if(k==2)cout<<i<<endl;
        }
    }

I don't understand why this doesn't work.Can I please receive the correct code for this exercise?Please do not use functions.

[jonnin]

1) what is k doing? Why isnt it just if !n%j print?
2) you only have to go to sqrt n+1 in the inner loop, which will become slow in a hurry.
3) n is useless, just use i.

[bokisof]

I am here just to say about efficiency. This is not efficient algorithm. Search google for Sieve of Eratosthenes, which is efficient for finding primes in given interval.