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In this tutorial, we will write a program to print prime numbers in a given range in C language. If you have to find all the prime numbers between some given ranges for example (39 to 48); to perform this task you will need a loop which will start from the starting range and ends at an ending range, and you will need a function which will check that the given number is prime or not as shown in the figure below.
<img src="https://cwh-full-next-space.fra1.digitaloceanspaces.com/videos/c-practice-programs-in-hindi-10/base64.webp" />
Figure 1: Find Prime Number
As shown in figure 1, we have a &ldquo;for&rdquo; loop which will start from the &ldquo;n1&rdquo; and ends at &ldquo;n2&rdquo;; &ldquo;n1&rdquo; is our starting range and &ldquo;n2&rdquo; is our ending range. The &ldquo;if&rdquo; condition inside the loop will call the function &ldquo;isPrime&rdquo;; the function &ldquo;isPrime&rdquo; will check if the given number is prime or not.
To determine whether a number is a prime number or not we have to check from (2 to n-1) that if that number is divisible with some number. If the number is divisible then it will not be a prime number but if the number is not divisible by any number from (2 to n-1) then the number is a prime number.
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Note: But the main thing to note here is that we can also check whether the number is prime or not by checking the number form (2 to &radic;n) rather than checking from (2 to n-1) to minimize the execution time.
An example program to print prime number in a given range in C language is shown below
<pre class="language-cpp"><code>int isPrime(int n){

 for (int i = 2; i*i &lt;= n; i++)

 {

 if (n%i == 0){

 return 0;

 }

 }

 return 1;

}</code></pre>
Code Snippet 1: isPrime Function
As shown in code snippet 1, we have written a function that will check whether a number is a prime number or not.
<ol>
<li>The function takes 1 integer parameter &ldquo;n&rdquo;; the parameter &ldquo;n&rdquo; will be the number which will be checked whether it is a prime number or not.</li>
<li>We have used the &ldquo;for&rdquo; loop which will traverse from (2 to &radic;n); at each iteration, the value of the variable &ldquo;n&rdquo; will be checked if it is divisible by some number.</li>
<li>If the value of the variable &ldquo;n&rdquo; is not divisible by any number from (2 to &radic;n) then the function will return &ldquo;1&rdquo;; otherwise the function will return &ldquo;0&rdquo;</li>
</ol>
<pre class="language-cpp"><code>int main(){

 int n1, n2;

 printf("Enter first number\n");

 scanf("%d", &amp;n1);

 printf("Enter second number\n");

 scanf("%d", &amp;n2);</code></pre>
Code Snippet 2: Main Program 1
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As shown in Code snippet 2,
<ol>
<li>We have declared two integer variables &ldquo;n1&rdquo; and &ldquo;n2&rdquo;; these variables will be used to store the input from the user.</li>
<li>The function &ldquo;printf&rdquo; is used to print &ldquo;Enter first number&rdquo; and the function &ldquo;scanf&rdquo; is used to get input from the user which will be stored in the variable &ldquo;n1&rdquo;</li>
<li>The function &ldquo;printf&rdquo; is used to print &ldquo;Enter second number&rdquo; and the function &ldquo;scanf&rdquo; is used to get input from the user which will be stored in the variable &ldquo;n2&rdquo;</li>
</ol>
<pre class="language-cpp"><code>printf("The prime numbers between %d and %d are: ",n1, n2);

 for (int i = n1; i &lt;= n2; i++)

 {

 if(isPrime(i)){

 printf("%d ", i);

 }

 }

 return 0;

}</code></pre>
Code Snippet 3: Main Program 2
As shown in a code snippet 3,
<ol>
<li>The function &ldquo;printf&rdquo; is used to print &ldquo;The prime numbers between %d and %d are:&rdquo;; the main thing to note here is that at the place of &ldquo;%d&rdquo; the value of the variables &ldquo;n1&rdquo; and &ldquo;n2&rdquo; will be printed</li>
<li>The &ldquo;for&rdquo; loop is used to traverse from the starting range till the ending range; the variable &ldquo;n1&rdquo; is the starting number and the variable &ldquo;n2&rdquo; is the ending number.</li>
<li>In the &ldquo;for&rdquo; loop body the function &ldquo;isprime&rdquo; is called inside the &ldquo;if&rdquo; condition. The number will be printed when the &ldquo;if&rdquo; conditions get true</li>
</ol>
The output of the following program is shown in the figure below
<img src="https://cwh-full-next-space.fra1.digitaloceanspaces.com/videos/c-practice-programs-in-hindi-10/base64_rUeKjsg.webp" />
Figure 2: Program Output
As shown in figure 2, we have given the number &ldquo;3&rdquo; as input for the first number and the number &ldquo;29&rdquo; as input for the second number. In the output, all the numbers between &ldquo;3&rdquo; and &ldquo;29&rdquo; which were prime numbers get printed.
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