Computer Science Canada

Prime Number Finder

Author:

TheXploder [ Fri Feb 20, 2004 12:39 pm ]

Post subject:

Prime Number Finder

Here is a program that finds prime numbers (divisible by itself and 1):

code:

var c, number : int := 0

loop
for decreasing i : number - 1 .. 2
if number mod i > 0 then
c := c + 1
end if
end for

if c = number - 2 then
put "Number: ", number, ", Prime number."
c := 0
else
put "Number: ", number, ", is not a Prime number."
c := 0
end if

number := number + 1
delay(10)
end loop

This could be sead up a bit, if I cancel out all numbers with a 5 or 0 at the end, or the numbers that are divisible by a previous prime number, can't be prime anymore...

I used this website to check them aswell: http://www.utm.edu/research/primes/lists/small/1000.txt

If you like please play around with it and try to beat me at finding the prime numbers: I am currently at prime number: 12739

Very Happy

ohh, wait: 16229

Author:	Tony [ Fri Feb 20, 2004 2:10 pm ]
Post subject:
maybe you should check out this tutorial

Author:	the_short1 [ Sat Feb 21, 2004 11:11 pm ]
Post subject:
hahah... yea Tony's prog... it worked in 12 sec to produce to 1million produces a text file will all prime numbers in it... from 2 > million (with a 120 MHZ peice of crap) WOW... that post is old too... 1y... at time when admins didnl;t have steady 2000 bits

Author:	TheXploder [ Sat Feb 21, 2004 11:46 pm ]
Post subject:
thanx for that program Tony...

Author:	Andy [ Sun Feb 22, 2004 2:00 pm ]
Post subject:
if u want a really good one, do some string manipulation, so u can store 255 digit numbers

Author:	Tony [ Sun Feb 22, 2004 11:47 pm ]
Post subject:
why not just use a char array then? you can make your arrays much larger then 255

Author:	Andy [ Mon Feb 23, 2004 10:49 am ]
Post subject:
good point

Author:	Andy [ Mon Feb 23, 2004 10:50 am ]
Post subject:
how about a flexiable array of strings?

Author:	rizzix [ Tue Feb 24, 2004 11:59 pm ]
Post subject:
aah but turing arrays have a limit of 1M elements. using a string class i created will let u manipulate on an infinite number of characters. (or maybe untill u exhaust all the free memory in RAM)

Author:	Tony [ Wed Feb 25, 2004 12:58 am ]
Post subject:
you can always start writing numbers down on your harddrive

Author:

BlAcK TuRtLe [ Sun Feb 29, 2004 2:34 pm ]

Post subject:

This is a variation of your code which lets the user enter a number then finds out whether or not its prime.

code:

var x, num : int := 0
loop
put "Enter a number(-99 to exit)"
get num
exit when num = -99
for decreasing y : num - 1 .. 2
if num mod y > 0 then
x := x + 1
end if
end for
if x = num - 2 then
put num, ", is a prime number."
x := 0
else
put num, ", is not a Prime number."
x := 0
end if
delay (2000)
cls
end loop
cls

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