Recently I had an interview for an internship position with Volocopter. It is an Urban Air Mobility (UAM) company based in Germany. As far as I know, this company is one of the most advance in UAM competition.

One part of the interview was an online coding. The interviewer asked me to “provide a list of all prime number up to 1000”. I found this question interesting as a there’s only one characteristic of a prime number.

A prime number is defined as a number greater than 1 whose factors are 1 and itself.

How do we implement it in a code? I wrote my code on my Github repository.

The idea of the code is pretty simple. First of all, we need to check if a number is a prime number or not. We can implement this by checking the **modulo** this particular number with a prime number. If the modulo is zero, this particular number is not a prime number.

Since we need to give list of the prime number up to a certain number, we can make a loop to go to reach that upper limit. In this case, we can use **for loop**. The first for loop will iterate up to the upper limit.

We should calculate the modulo of that particular number with another number. At first, I compared it by using for loop from 1 to that number but this is not efficient. An efficient way is to compare it only with a prime number, as I mentioned earlier. Therefore, we can initiate **list of prime number** and **iterate** through this list. If a particular number is a prime number, then add this number to list of prime number.

There you go! List of prime number in an easy way.

**Note**: *During the interview, the interviewer helped me figuring out what I have to do. I didn’t finish the whole code during the interview since it was stopped when the idea was pretty obvious.*