Example
Input
Input lower limit: 1 Input upper limit: 20
Output
Prime numbers between 1-20: 2, 3, 5, 7, 13, 17, 19
/**
* C program to print all prime numbers between 1 to n
*/
#include <stdio.h>
int main()
{
int i, j, end, isPrime; // isPrime is used as flag variable
/* Input upper limit to print prime */
printf("Find prime numbers between 1 to : ");
scanf("%d", &end);
printf("All prime numbers between 1 to %d are:\n", end);
/* Find all Prime numbers between 1 to end */
for(i=2; i<=end; i++)
{
/* Assume that the current number is Prime */
isPrime = 1;
/* Check if the current number i is prime or not */
for(j=2; j<=i/2; j++)
{
/*
* If i is divisible by any number other than 1 and self
* then it is not prime number
*/
if(i%j==0)
{
isPrime = 0;
break;
}
}
/* If the number is prime then print */
if(isPrime==1)
{
printf("%d, ", i);
}
}
return 0;
}Program to print prime numbers in given range
/**
* C program to print all prime numbers between 1 to n
*/
#include <stdio.h>
int main()
{
int i, j, start, end;
int isPrime;
/* Input upper and lower limit to print prime */
printf("Enter lower limit: ");
scanf("%d", &start);
printf("Enter upper limit: ");
scanf("%d", &end);
printf("All prime numbers between %d to %d are:\n", start, end);
// Make sure that lowerlimit does not go below 2
// Since 2 is first prime number
if(start < 2)
start = 2;
/* Find all Prime numbers between 1 to n */
for(i=start; i<=end; i++)
{
/* Assume that the current number is Prime */
isPrime = 1;
/* Check if the current number i is prime or not */
for(j=2; j<=i/2; j++)
{
/*
* If i is divisible by any number other than 1 and self
* then it is not prime number
*/
if(i%j==0)
{
isPrime = 0;
break;
}
}
/* If the number is prime then print */
if(isPrime==1)
{
printf("%d, ", i);
}
}
return 0;
}
/*
Output :
Enter lower limit: 1
Enter upper limit : 100
All prime numbers between 1 to 100 are:
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97,
*/