Need Help.!!!!!
It's about C programing atually.
I was writing a program to check whether number is prime or not.
.
I used while loop.
program i wrote -
-------------------------------------------------
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number\n\n-->");
scanf("%d",&a);
while(a%i==0 && i<a)
{printf("Number is composite");}
i++;
printf("\n\nNumber is prime");
getch();
}
----------------------------------------------
.
here in output if number is prime it shows - number is prime
if it's composite then it goes on typing "number is composite" infinite times...
.
.
HELP ME ON THIS PLEASE.
I'm just a beginner.
I was writing a program to check whether number is prime or not.
.
I used while loop.
program i wrote -
-------------------------------------------------
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number\n\n-->");
scanf("%d",&a);
while(a%i==0 && i<a)
{printf("Number is composite");}
i++;
printf("\n\nNumber is prime");
getch();
}
----------------------------------------------
.
here in output if number is prime it shows - number is prime
if it's composite then it goes on typing "number is composite" infinite times...
.
.
HELP ME ON THIS PLEASE.
I'm just a beginner.
i++ is outside the loop. Your loop only checks whether the number is odd, not prime as i is always 2 in the loop.
Note that even if you do that, it will still not work right. Your logic is wrong. if a is odd, the loop will not be entered no matter what you write in it.
Note that even if you do that, it will still not work right. Your logic is wrong. if a is odd, the loop will not be entered no matter what you write in it.
i see .
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number--> ");
scanf("%d",&a);
if(a%i==0 && i<a)
printf("\nNumber is composite\n");
else
printf("\nNumber is prime\n");
}
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number--> ");
scanf("%d",&a);
if(a%i==0 && i<a)
printf("\nNumber is composite\n");
else
printf("\nNumber is prime\n");
}
thnx for help.
But i got the solution.
here -
-------------------------------------------------------------
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number\n\n-->");
scanf("%d",&a);
if(a%i==0 && i<a)
{printf("\n\nNumber is composite");}
else
{printf("\n\nNumber is prime");}
i++;
getch();
}
---------------------------------------------------------------
But i got the solution.
here -
-------------------------------------------------------------
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number\n\n-->");
scanf("%d",&a);
if(a%i==0 && i<a)
{printf("\n\nNumber is composite");}
else
{printf("\n\nNumber is prime");}
i++;
getch();
}
---------------------------------------------------------------
@ googleking.
.
hey u check only if number is divisible by 2 or not. That is not test for prime. It is test for even and odd.
The program i wrote(corrected-lataste version) is correct. I have checked output. It's perfect. :)
.
hey u check only if number is divisible by 2 or not. That is not test for prime. It is test for even and odd.
The program i wrote(corrected-lataste version) is correct. I have checked output. It's perfect. :)
VirSawant, googleking
You both posted the exact same code. You both just test for evens or odds. Just try 9 and see how it fails.
To check if a number is prime you need to check that it is not divisible by any number smaller than itself.
Have a for loop i = 2 to a-1. If a is divisible by i, print "not prime" else keep looping.
You both posted the exact same code. You both just test for evens or odds. Just try 9 and see how it fails.
To check if a number is prime you need to check that it is not divisible by any number smaller than itself.
Have a for loop i = 2 to a-1. If a is divisible by i, print "not prime" else keep looping.
@ hamsterman: Boring! Use Trial Division: http://en.wikipedia.org/wiki/Trial_division
This way the OP may learn some actual math coding...
This way the OP may learn some actual math coding...
oh ya i see
but for some numbers it's working properly.
67 - prime
12- composite
...
what shoud i do now???
i initiated i with 2 and after checking divisiblity i increased it by 1 n then agained checked... untill i<the given number... what's wrong with this????
but for some numbers it's working properly.
67 - prime
12- composite
...
what shoud i do now???
i initiated i with 2 and after checking divisiblity i increased it by 1 n then agained checked... untill i<the given number... what's wrong with this????
@ OP: Use a different technique to determine if a number is prime or not. Both hamsterman and I have given valid answers on what to do next.
thnx.
i'll see trial division and let you people know.
I'm a beginner... will need help ...
i'll see trial division and let you people know.
I'm a beginner... will need help ...
@hamsterman -
***********************************************
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number\n\n-->");
scanf("%d",&a);
for(i=2;i++;i<a)
{if(a%i==0)
{printf("\n\nNumber is composite");}
else
{printf("\n\nNumber is prime");}
}
getch();
}
******************************************
what about this??????????
***********************************************
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number\n\n-->");
scanf("%d",&a);
for(i=2;i++;i<a)
{if(a%i==0)
{printf("\n\nNumber is composite");}
else
{printf("\n\nNumber is prime");}
}
getch();
}
******************************************
what about this??????????
Last edited on
superb...............
thank u all
.
@computergeek01
i'll also check about trial division.. just reading that...
.
*************************************************
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number\n\n-->");
scanf("%d",&a);
for(i=2;i++;i<a)
{if(a%i==0)
{printf("\n\nNumber is composite");
break;}
else
{printf("\n\nNumber is prime");
break;}
}
getch();
}
********************************************
thank u all
.
@computergeek01
i'll also check about trial division.. just reading that...
.
*************************************************
#include<stdio.h>
#include<conio.h>
main()
{
int a,i;
i=2;
printf("Enter the number\n\n-->");
scanf("%d",&a);
for(i=2;i++;i<a)
{if(a%i==0)
{printf("\n\nNumber is composite");
break;}
else
{printf("\n\nNumber is prime");
break;}
}
getch();
}
********************************************
no. read up on for loops.. do you test your code at all ? (Try 25)
also, http://www.cplusplus.com/forum/articles/42672/
and properly format your code..
also, http://www.cplusplus.com/forum/articles/42672/
and properly format your code..
ya i tested for 25 ............. it's not working again!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :(
but why is it so... it's now showing 9 a composite... so i was happy.. but today i checked 25 ... shet... it says prime...................................
but why is it so... it's now showing 9 a composite... so i was happy.. but today i checked 25 ... shet... it says prime...................................
Firstly, the syntax of for loop is
Read my post where I explained the algorithm again.
for( initial state; condition; increment ){ ... }. You mixed that up. Secondly, both if conditions result in a break, so that loop will never loop.Read my post where I explained the algorithm again.
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