In this C program, we will find all prime numbers between 1 to N. A Prime number is a natural number greater than 1 that is only divisible by either 1 or itself.
All numbers other than prime numbers are known as composite numbers. There are infinitely many prime numbers, here is the list of first few prime numbers
2 3 5 7 11 13 17 19 23 29 31 37....
Required Knowledge
Algorithm to check whether a number is prime number or not
Let, N be a positive number.
Let, N be a positive number.
- For every number i, between 2 to N/2(2<= i <= N/2) check whether i divides N completely(check If i is a factor of N).
- if (N % i == 0), then N cannot be a Prime number.
- If none of the number between 2 to N/2 divides N completely then N is a prime number.
C program to print all prime numbers between 1 to N using for loop
#include<stdio.h>
int main(){
int N, i, j, isPrime, n;
printf("Enter the value of N\n");
scanf("%d",&N);
printf("Prime numbers between %d to %d\n", 1, N);
for(i = 2; i <= N; i++){
isPrime = 0;
/* Check whether i is prime or not */
for(j = 2; j <= i/2; j++){
if(i % j == 0){
isPrime = 1;
break;
}
}
if(isPrime==0 && N!= 1)
printf("%d ",i);
}
return 0;
}
Output
Enter the value of N 50 Prime numbers between 1 to 50 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47
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