# C program to find prime numbers in given range using functions

Write a function in C programming to find prime numbers using function. How to find all prime numbers between two intervals using functions. Display all prime numbers between a given range using function in C programming.

Example

Input

```Input lower limit: 10
Input upper limit: 50```

Output

`Prime numbers between 10-50 are: 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47`

## Declare function to find all prime numbers in given range

1. First give a meaningful name to our function. Say `printPrimes()` function will print all prime numbers in given range. Declare one more function say `int isPrime(int num);` to check prime number.
2. Since we need to print prime numbers in a given range. Hence, we must pass two parameters to function i.e. the upper and lower limit. Pass two integers to the function say `printPrimes(int lowerLimit, int upperLimit);`.
3. Finally, function will print all prime numbers in given range returning nothing. Therefore, the return type of the function must be `void`.

Function declaration to print all prime numbers in given range - void printPrimes(int lowerLimit, int upperLimit);

## Program to find all prime numbers in given range using function

``````/**
* C program to list all prime number between an interval using function.
*/

#include <stdio.h>

/* Function declarations */
int isPrime(int num);
void printPrimes(int lowerLimit, int upperLimit);

int main()
{
int lowerLimit, upperLimit;

printf("Enter the lower and upper limit to list primes: ");
scanf("%d%d", &lowerLimit, &upperLimit);

// Call function to print all primes between the given range.
printPrimes(lowerLimit, upperLimit);

return 0;
}

/**
* Print all prime numbers between lower limit and upper limit.
*/
void printPrimes(int lowerLimit, int upperLimit)
{
printf("All prime number between %d to %d are: ", lowerLimit, upperLimit);

while(lowerLimit <= upperLimit)
{
// Print if current number is prime.
if(isPrime(lowerLimit))
{
printf("%d, ", lowerLimit);
}

lowerLimit++;
}
}

/**
* Check whether a number is prime or not.
* Returns 1 if the number is prime otherwise 0.
*/
int isPrime(int num)
{
int i;

for(i=2; i<=num/2; i++)
{
/*
* If the number is divisible by any number
* other than 1 and self then it is not prime
*/
if(num % i == 0)
{
return 0;
}
}

return 1;
}``````

Output

```Enter the lower and upper limit to list primes: 10 50
All prime number between 10 to 50 are: 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47,```

Happy coding 😉 