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if(isprime)...

what does that mean?i thought if statments should be boolean(can either be true or false).

i'll just adjust it so that it contains an array.it is also a requirement.and by doing so, is it right that i use variable "i" as the index of the array elements?

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The text above is a follow-up to ...

-----Question-----

this was based on the sieve of eratosthenes.I have tried doing it but we are required to use 2 for loops and i have no idea why is there a need to do so.what will you use as the limit/termination condition in the loop?i tried the input value N as the limit to the first loop but it did not work.sorry i am a nemwbie to C++ and thanks for helping.!

-----Answer-----

Dear farrah !

The problem is of course simple , because finding all the prime numbers in a certain range of course expect 2 for loops!

one ( the outer for loop) selects the value under discussion , and the inner for loop determines its actually a prime number or not!

Here i present you a simple my simple code to find all prime numbers in a given range!

#include<iostream.h>

void main()

{

int n , isprime;

cout<<"Enter range :";

cin>>n;

for( int i = 2 ; i <= n ; i++)

{

isprime = 1;

for( int j = 2 ; j <= i ; j++)

{

if( i == j)

continue;

else if( i % j == 0)

isprime = 0;

}

if(isprime)

cout<<i<<" ";

}

}

Thanks and regards !

Prince M. Premnath

Dear farrah !

Actually its not a problem , purpose of the variable "isprime " here i used to save only two values ( say 1 true 0 false ) , You may ask why i declared it as a 'int ' instead of 'boolean ' , here is the answer ! I actually programmed that solution in Turbo C++ 3.0 ( Of course a old compiler ) that does not support the data type 'boolean' ,But im sure you won't get any problem if you declare it as a boolean data type ,

What you have to do is just to alter the 3 statements !

in Declaration : boolean isprime;

and the statement : isprime = 1; sholue be replaced with isprime = true; similar change in case of isprime = 0; replacing 0 by false.

Statement: if(isprime)..

if statement expect only two conditions ie 0 and non zero ,

if(0)/* condition fails */

if(1)/* condition true */

if the variable 'isprime' holds 0 then the statement if(isprime) .. is equvalent to if(0).

Use of i as index?

Of course i is just a variable! there is no special meaning of using i as an index , except its the starting letter of the word "Index" - the term likely used in arrays!

You are free to use any variables replacing 'i' , ( say 'a' , 'b' ....) .

Thanks and regards !

Prince M. Premnath

Years of research in C/C++ Will bring you all facts regarding , OOPS , SVGA , MOUSE , BIOS , IVT , Feel free to query me :-)

More than 5 years**Education/Credentials**

MCA