# C Program to Display Prime Numbers Between Two numbers

Prime numbers between two numbers we will also learn how to display prime number between 1 to n numbers. Now first of all we learn about prime numbers.

- 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

**Define prime number**

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….

step 1. in step 1 processors are given to include header file for prime numbers

step 2. we used main function

step 3. we have declared variables

step4. two numbers are inputed with the help of printf and scanf fuction

step5. in this step external loop is given here we for loop which increase their value from 1 to next and so on

### Algorithm for prime number

we just write algorithm for 1 to n number you can change it according to your need and requirements

alogorighm

**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.

Example of Program

```
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
long i,prime,j,n1,n2;
printf("Enter start and end numbers for prime");
scanf("%ld %ld",&n1,&n2);
for(i=n1;i<=n2;i++)
{
prime=1;
for(j=2;j<i;j++)
{
if(i%j==0)
{
prime=0;
break;
}
}
if(prime==1)
printf("%ld\t",i);
}
getch();
}
```

**Output**

Enter two numbers(intervals): 20 50 Prime numbers between 20 and 50 are: 23 29 31 37 41 43 47