Thread: /i need help in C- program for prime numbers plzZzZ

None of us here will do your work for you (this sounds like a homework situation, which there is a policy on this board not to do). But we will try to help you learn how to do it.

The first step is to figure out how you would solve the problem by hand, and write down each step. Once you have that, it shouldn't be THAT hard to write a C-program to solve the problem.

Also, if you haven't done that yet, try writing a program that just prints numbers from one to n where n is (say) 100, 200 or 300.

Then you just have to add "is x a prime then print x" instead of the simple print x in "print all numbers".

This technique of development is called "stepwise refinement", and works quite well for small project like this.

--
Mats

You could also google "sieve of eratosthenes" for an algorithm to find prime numbers. But like matsp said, no-one will do your homework for you!

QuantumPete

Using sieve if you don't have a good understanding of programming is probably not a particularly good idea - trivial [1] method is much easier to implement.

[1] using the "brute force and ignorance" method is never ideal for REAL work, but since this is intended for relatively small numbers and most likely a teaching excercise early on in a student course, it's probably the BEST method.

--
Mats

Fair enough :-D I remember those days at uni, when efficiency was not #1 priority in coding...

QuantumPete

I've been noticing this influx of users who use this "i'm a n00b" grammar, it's getting worse, i'm becoming afraid to post here.

i'll have to start going to gamedev more

OOOops okay no prob but slowly on me .... i didnt expect someone to do it for me coz i will hav it in exam so i hv to understand it ...i tried my best ok i will tell u wat i did was like wat
i used for statement to print numbers from 1 to 200 and then i just put if statement under it
if (x%2=!0 || x%3=!0 || x%4=!0 ...................||x%9=!0) i mean not equal
printf("%d",a)
but i couldnt continue it worked for %2=! and 3 but the rest didnt work . . . i will try to post wat i did next time coz now i just replied .. thnx anyway..

Code:

#include<stdio.h>
main()
{
int n,i,f=0;
printf("enter any number");
scanf("&#37;d",&n);
for(i=2;i<n;i++)
{
if(n%i==0)
f=1;
}
if(f==1)
printf("entered number is not a prime");
else
printf("entered number is a prime");
getch();
}

Originally Posted by shuaib.akram

Code:

#include<stdio.h>
main()
{
int n,i,f=0;
printf("enter any number");
scanf("%d",&n);
for(i=2;i<n;i++)
{
if(n%i==0)
f=1;
}
if(f==1)
printf("entered number is not a prime");
else
printf("entered number is a prime");
getch();
}

There we go, the home work is done. lol

ssharish2005

Thank you so much!