Code archives/Algorithms/Prime Finder

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Prime Finder by Nathaniel
(Posted 20 years ago)
The program first asks which number to start calculating to see if it is prime. It then continues with the next consecutive number. (It does this until you press the esc. key.) I don't suggest putting in a number that's over 5000.

Have Fun!
Open in online IDE
;Prime Finder
;Created by: Bubble Boy

Graphics 800,600,16,2
SetBuffer BackBuffer()

AppTitle "Prime Finder"

number#=1
divisor#=1
quotient#=0
rounded=0
prime=0
go=0


Color 250,250,86
Print "PRIME FINDER"

number#=Input$("What number do you want me to start with? ")


While Not KeyHit(1)

Color 250,250,86
Print number#
Flip

While go = 0

   quotient# = number# / divisor#
   rounded=Int( quotient# )

   Color 50,255,50
   Print quotient# + " = " + number# + " / " + divisor#


   If divisor# > 1
   If quotient# = rounded
      prime = 0
      go = 1
   Else 
      prime = 1

   End If   
   End If


Delay 20

If KeyDown(1)
   End
End If

If divisor# = number#
   prime = 1
   go = 1
End If

If number# = 1
   prime = 0
   go = 1
End If

divisor# = divisor# + 1




Wend

If prime = 1
   Color 250,250,86
   Print number#
   Color 255,50,50
   Print "PRIME"

   Flip()


Else If prime = 0
   Color 250,250,86
   Print number#
   Color 50,50,255
   Print "NOT PRIME"
   Flip()
End If
Print " "

Delay 2000

go=0
prime=0
number#=number# + 1
divisor#=1
quotient#=0

Wend

End

Comments

erbbysam
(Posted 20 years ago)
;Prime Finder
;Created by: Bubble Boy
;edited by: erbbysam


SetBuffer BackBuffer()

AppTitle "Prime Finder"

fileout = WriteFile("primes.txt") 

number#=1
divisor#=1
quotient#=0
rounded=0
prime=0
go=0


Color 250,250,86
Print "PRIME FINDER"

number#=0


While Not KeyHit(1)


While go = 0

   quotient# = number# / divisor#
   rounded=Int( quotient# )

   If divisor# > 1
   If quotient# = rounded
      prime = 0
      go = 1
   Else 
      prime = 1

   End If   
   End If

If divisor# = number#
   prime = 1
   go = 1
End If

If number# = 1
   prime = 0
   go = 1
End If

divisor# = divisor# + 1




Wend

If prime = 1
 
WriteLine( fileout, number# ) 

End If

go=0
prime=0
number#=number# + 1
divisor#=1
quotient#=0

Wend
CloseFile( fileout ) 

End

this uses the code above to output every prime number that it can find starting at 0 to a file. After about a minute it will find the first 10,000 primes (or every prime between 2 and 100000 :D)

Subirenihil
(Posted 20 years ago)
Zzzz I've had MUCH better code for finding prime numbers for years. I can calculate the first ten million prime numbers in half an hour using my code.

Tip #1: A number is prime if it is not divisible by a prime number less than or equal to it's square root.
Tip #2: If number Mod divisor=0 then prime=False

I will now post my code to the archives.
Calculating Primes

And here is code that trumps mine FAST Sieve of Eratosthenes

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