Thread: Hello about my program

You want to store 50 primes, but your array is of size 40! It should be 50, shouldn'it

You have

Code:

cin>>"y";

but what you meant to write is

Code:

cin >> y;

I do not see any find() method in your post.

You can access the i-th element of an array, with the [] operator.
This code is storing value 5 in the first cell of an int array of size 10.

Code:

int A[10]
A[0] = 5;

Sorry for the mistakes that I did,

Yes I'll correct them but is it true that if I take any number from a user as input using the "cin", do I have to manually enter each value taken from the user in the array?




Thanks

You could do this

Code:

#include <iostream>

int main()
{

        int N = 50;
        int A[N];
        std::cout << "Input " << N << " integers\n";
        for(int i = 0 ; i < N ; ++i)
                std::cin >> A[i];
        std::cout << "Output\n";
        for(int i = 0 ; i < N ; ++i)
                std::cout << A[i] << "\n";
        return 0;
}

Here, we read N integers into the array and then we print the array.

In this point, it is the same.
In other words

Code:

for(i = 0 ; i < 5 ; ++i)

is the same (for us) with

Code:

for(i = 0 ; i < 5 ; i++)

Recall, that in the 1st piece of code, the incremental operator is prefix and in the 2nd, postfix!

In order to take a smell of what this means, consider this simple example.

Code:

#include <stdio.h>

int main(void)
{
        int i = 0 ;
        // First print i and then increment i
        printf("%d\n", i++);

        // First increment i and then print i
        printf("%d\n", ++i);

        return 0;
}

First think what the output will be and then run the code to test your thought.
Notice that incremental (or decremental) operators can be a caveat. If you are not sure if it is correct to use it in a line of code, avoid it.

I declared variable "i" in the for loop. In other words, I initialized this variable in the scope of the for loop. As a result, this variable leaves inside the for statement and its body only.

Originally Posted by student111

Is it true that we use variables and arrays outside of the main function only when we make classes?

No, e.g., when you write a non-member function other than the main function, you will probably use one or more variables.