**C Programs For Prime Number: **In this article, we will know what is the prime number. and at the same time, we will know how to **find **the **prime number **in c as well as an example with **explanation**. We will perform this **example **in different ways.

## What is a prime number?

The prime number is the whole number. Which is greater than 1. Which is evenly dived from one or its own number.** It is called a prime number.**

**Example:** 2 is the prime number which is divided evenly from 1 or 2 itself.

**Other example:** 2,3,5,7,11, etc.

## Prime Number Algorithm in c

**Start**- The user will get an integer variable X inter
- Will divide the variable with (X-1 to 2)
- If X is divisible with any value (X-1 to 2) then not prime
- else X is a prime number
**Stop**

We will perform the program of a prime number in c in the following way.

- The prime number using Function
- Prime number program in c using for loop
- Prime number program in c using while loop
- Print Prime Numbers from 1 to n

## Prime Number Program in C

### The prime number using the function

#include <stdio.h>

int prime_find (int);

main ()

{

int a, b;

printf ("Enter Integer Number to Find Prime or Not. \ n");

scanf ("% d", & a);

b = prime_find (a);

if (b == 1)

printf ("% d is prime. \ n", a);

else

printf ("% d is not prime. \ n", a);

return 0;

}

int prime_find (int x)

{

int y;

for (y = 2; y <= x - 1; y ++)

{

if (x% y == 0)

return 0;

}

return 1;

}

**Input**

Enter Integer Number to Find Prime or Not.5

**Output**

5 is prime

**Prime number program in c using for loop**

#include <stdio.h>

int main ()

{

int a, b, c = 0;

printf ("Enter Integer Number to Find Prime or Not. \ n");

scanf ("% d", & a);

for (b = 2; b <= a / 2; ++ b)

{

// check for non prime number

if (n% b == 0)

{

c = 1;

break;

}

}

if (c == 0)

printf ("% d is a prime number.", a);

else

printf ("% d is not a prime number.", a);

getch ();

}

**Input**

Enter Integer Number to Find Prime or Not.5

**Output**

5 is a prime number

### Prime number program in c using while loop

#include <stdio.h>

int main ()

{

int n, i, count = 0;

int a, b, c = 0;

printf ("Enter Integer Number to Find Prime or Not. \ n");

scanf ("% d", & a);

b = 2;

while (b <= a / 2)

{

// check for non prime number

if (a% b == 0)

{

c = 1;

break;

}

b ++;

}

if (c == 0)

printf ("% d is a prime number.", a);

else

printf ("% d is not a prime number.", a);

getch ();

}

**Input**

Enter Integer Number to Find Prime or Not.5

**Output**

5 is a prime number

### Print Prime Numbers from 1 to n

#include <stdio.h>

int main () {

int a, b, count, n;

printf ("Enter Rang For To Find Prime Number");

scanf ("% d", & n);

for (a = 1; a <= n; a ++) {

count = 0;

for (b = 2; b <= a / 2; b ++) {

if (a% b == 0) {

count ++;

break;

}

}

if (count == 0 && a! = 1)

printf ("% d", a);

}

return 0;

}

**Input**

Enter Rang For To Find Prime Number 5

**Output**

2 3 5

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