Wrox Programmer Forums
|
Welcome to the p2p.wrox.com Forums.

You are currently viewing the Assembly Language section of the Wrox Programmer to Programmer discussions. This is a community of software programmers and website developers including Wrox book authors and readers. New member registration was closed in 2019. New posts were shut off and the site was archived into this static format as of October 1, 2020. If you require technical support for a Wrox book please contact http://hub.wiley.com
  #1 (permalink)  
Old May 24th, 2009, 05:22 PM
Registered User
 
Join Date: May 2009
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Default Prime number program help

I need help with a program that finds and displays all of the prime numbers (eg, 1, 2, 3, 5, 7, 11, 13, 17, 19) from 1 to 20. I have most of the code, but am unsure where to go from here, the output displays all numbers from 1 to 20. Here is what I have so far:
Code:
include 'emu8086.inc'
org  100h ; set location counter to 100h
jmp CodeStart
DataStart:
   max dw 20
   space db " ", 0
CodeStart:
   mov bx, 1
   
   
   call IsPrime  
   cmp dx, 0
   
   LoopStart:   
   
       ; must be a prime
       mov ax, bx
       call print_num
       
       ; print a space
       mov si, offset space
       call print_string
       
       add bx, 1
       cmp bx, max
   jle LoopStart
   
   ret
       
    
   IsPrime PROC
       ; uses a loop to determine if number in bx is prime
       ; upon return if bx not prime dx will be 0, otherwise dx > 0
       ; we only have to test divisors from 2 to bx/2
       
       ; prepare to divide dx:ax / 2
       mov ax, bx         
       mov dx, 0 
       mov cx, 2  
       div cx
       
       ; move result into si for loop
       mov si, ax
       
       ; assume the value is prime
       mov dx, 1
       
       ; start loop at 2
       mov cx, 2
       
       PrimeLoop:
       
           ; compare loop count(in cx) and max loop value (in si)
           cmp cx, si
           
           ; jump out of loop if count(cx) > si
           ja StopLabel
       
           ; divide test value (in bx) by loop count (in cx)
           mov ax, bx
           mov dx, 0            
           div cx
           
           ; check remainder (in dx), if zero then we found a divisor
           ; and the number cannot be prime
           cmp dx, 0
           
           ; if dx = 0 then we found a divisor and can stop looking
           je StopLabel
           
           ; increment count
           add cx, 1
       
       jmp PrimeLoop
       
       StopLabel:
       
       ret
   IsPrime ENDP
   
DEFINE_PRINT_STRING
DEFINE_SCAN_NUM
DEFINE_PRINT_NUM
DEFINE_PRINT_NUM_UNS
  #2 (permalink)  
Old May 24th, 2009, 08:24 PM
Registered User
 
Join Date: May 2009
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Smile

Nevermind, I was able to figure out the solution on my own.
  #3 (permalink)  
Old January 10th, 2010, 07:29 AM
Authorized User
 
Join Date: Jan 2010
Posts: 12
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Quote:
Originally Posted by daddymac1213 View Post
Nevermind, I was able to figure out the solution on my own.
Can you post the solution?





Similar Threads
Thread Thread Starter Forum Replies Last Post
Validation For Phone Number and Mobile Number dhruthi.ram99 Javascript How-To 12 October 30th, 2011 07:24 AM
Setup Project: Program not added in Start>Program arif_1947 VS.NET 2002/2003 2 March 31st, 2005 06:40 AM
prime numbers code error.. amahja56 C++ Programming 1 January 19th, 2005 01:33 PM
Prime Number Counting. Help!! ajm235 C++ Programming 3 August 27th, 2004 12:00 PM





Powered by vBulletin®
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Copyright (c) 2020 John Wiley & Sons, Inc.