# Calculating Primes

Today I am going to talk about calculating primes.

Not the new Transformer movie in which Optimus Prime has to help the humans save the world.
I am talking about prime numbers in which the number is only divisable by one and itself.

The Algorithm that I am going to introduce is a brute force method for calculating prime numbers.
It is great for comparing the computing power of two machines by looking at overall execution times.

This routine consists in dividing n by each integer m which is greater than 1 and less than or equal
to the square root of n. If the result of any of these divisions is an integer, then n is not a prime;
otherwise, it is a prime.

I am going to use both the “Application Logging” and “Write Text File” classes that were discussed earlier to solve this problem.

I always like to create a high level program algorithm before starting any coding. I usually write it in psuedo code so that is program like in nature.

Calculating Primes Algorithm:

The table below has the Visual Basic (VB) Scripts used in the solution and the output files. I ran the program to calculate all the prime numbers less than or equal to 2.5 Million. The program executed in 91 seconds on a Dell i5 Laptop running Windows 7 – 32 bit operating system and found 183,072 prime numbers.

 mod-write-text-file.vbs Write Text File Class mod-app-logging.vbs Application Logging Class prg-calc-primes-v1.vbs Calculate Primes Program primes.cmd Primes Batch File prg-calc-primes-v1.log Primes Log File primes Primes Result File

This is a screen shot of the calculating primes VB Script excuting in a MS DOS command shell.

As you can see, the second time I ran the program it took 95 seconds. Just to show you that background processes like email, word, and etc. can have sligth performance impacts of heavy computational programs.

## One Thought to “Calculating Primes”

1. During my college years I never saw work as good as this. You display a lot of intelligence and detail within this article and I hope you continue to write these. This is very good.