Prime Number Program In C

Program to find whether a given number is Prime or Not


#include<stdio.h>

int main()
{
 /* Declaring variable for n=number, c=counter variable:holds 
 number of factor of 'n' */
 int n,c=0, i;
 
 // Inputting number
 printf("Enter number to check whether Prime or Not:");
 scanf("%d",&n);

 // Checking whether number valid or not
 if(n>0)
 {
  
 // Checking whether number is prime or not 
 for(i=1;i<=n;i++)
 {
  if(n%i==0)
    c=c+1;
 }
 
 if(c==2)
   printf("Prime Number");
 else
   printf("Not a Prime Number");
 }
 
 else 
   printf("Not a valid Number");

 return 0;
}

Program to print ( list ) all the prime number between 1 to n

#include<stdio.h>

int main()
{
 /* Declaring variable for n=number, c=counter variable:holds 
 number of factor of 'n' */
 int n,c, i,j;
 
 // Inputting number
 printf("Enter number till which you want to list prime number:");
 scanf("%d",&n);

 // Checking whether number valid or not
 
 if(n>0)
 {
  printf("List of Prime Numbers:");
 // Checking whether number is prime or not 
 for(i=1;i<=n;i++)
 {
  c=0;
  for(j=1;j<=i;j++)
  {
    if(i%j==0)
      c=c+1;
  }
 if(c==2)
   printf("%d ",i);
 }
 
 }
 else 
   printf("Not a valid Number");

 return 0;
}

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