# C Program to Print All Prime Numbers between 1 to N

• Write a C program to print all prime numbers between 1 to N using for loop.
• Wap in C to print prime numbers between 1 to 100.

Required Knowledge

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….

Algorithm to check whether a number is prime number or not

• 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>
#include<conio.h>

int main(){

int N, i, j, isPrime, n;

printf("To print all prime numbers between 1 to N\n");
printf("Enter the value of N\n");
scanf("%d",&N);

/* For every number between 2 to N, check
whether it is prime number or not */
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++){
/* Check If any number between 2 to i/2 divides I
completely If yes the i cannot be prime number */
if(i % j == 0){
isPrime = 1;
break;
}
}

if(isPrime==0 && N!= 1)
printf("%d ",i);
}
getch();
return 0;
}

Output

To print all prime numbers between 1 to N
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