Friends i have little bit problem in making a c language program.

I have to make a program which prints prime numbers from 1 to 500.

I make this program but with while loop then i was told to make it using for loop, which i tried but failed.

So kindly help me. Thanks

from,

john(pakistan)

john_hasan
0
Newbie Poster

## Recommended Answers

Jump to PostI dont know that high math, but I think I can do better.

`bool isPrime(int n) { bool prime ; int lim; if ( n == 0 || n == 1 || n % 2 == 0) return(false); prime = true; lim = (int)sqrt(n); for(int i=3; i<= …`

Jump to Post> for(int i=2; i<=((int)sqrt((double)n)); i++)

And it would be so much quicker if you didn't call sqrt() on every iteration of the loop!

n is constant (in this function), so it's root is constant also. Calculate it once and store in another variable to compare against.Also, since 2 …

Jump to PostI wouldn't call 2 a special case - it fits the general description perfectly; A number evenly divisible only by 1 and itself

Strictly that's not true because 1 is divisible by 1 and itself, but 1 isn't prime. I prefer:

A prime number has precisely two positive integer …

Jump to PostThis should be considerably although I'd bet not noticeably faster.

`#include <iostream> using namespace std; int main (){ int prim=3, div,i=2; cout<<1<<" "<<2<<" "; for (i; i<=500; i++){ div=3; while(div<=prim/3){ if (prim%div!=0){div+=2;} else {prim+=2;div=3;}} cout<<prim<<" "; prim+=2;} system("pause");}`

Why do you care about the speed anyways?

Jump to PostWhy do you care about the speed anyways?

If the developers didnt care for speed then u wouldn't be conviniently using your favourite OS u are usign right now without atlest swearing atleast 100 times a day regarding the slow loading times.

Dont forget that this is a C/ …

## All 37 Replies

Micko
2
Junior Poster

john_hasan
0
Newbie Poster

hollystyles
113
Veteran Poster

Salem
5,138
Posting Sage

hollystyles
113
Veteran Poster

Salem
5,138
Posting Sage

shavez_israr
0
Newbie Poster

Salem
5,138
Posting Sage

hollystyles
113
Veteran Poster

hollystyles
113
Veteran Poster

iamthwee
1,547
Banned
Featured Poster

hollystyles
113
Veteran Poster

dude543
2
Light Poster

hollystyles
commented:
good solution
+2

Salem
5,138
Posting Sage

hollystyles
commented:
good feedback
+2

hollystyles
113
Veteran Poster

hollystyles
113
Veteran Poster

dude543
2
Light Poster

hollystyles
113
Veteran Poster

Bench
212
Posting Pro

hollystyles
113
Veteran Poster

portege
0
Light Poster

~s.o.s~
2,560
Failure as a human
Team Colleague
Featured Poster

portege
0
Light Poster

WolfPack
491
Posting Virtuoso
Team Colleague

~s.o.s~
2,560
Failure as a human
Team Colleague
Featured Poster

portege
0
Light Poster

WolfPack
491
Posting Virtuoso
Team Colleague

~s.o.s~
2,560
Failure as a human
Team Colleague
Featured Poster

Lerner
582
Nearly a Posting Maven

Be a part of the DaniWeb community

We're a friendly, industry-focused community of 1.21 million developers, IT pros, digital marketers, and technology enthusiasts learning and sharing knowledge.