C program uses a function to display prime numbers between intervals

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In this example, you will learn how to print all prime numbers between two numbers (input by the user).

To understand this example, you should understand the followingC programming languageTopic:

• C for loop

• C break and continue statements

• C function

• C user-defined function

To find all prime numbers between these two integers, the checkPrimeNumber() function was created. This functionCheck if a number is prime.

Prime numbers between two integers

#include  <stdio.h>
int  checkPrimeNumber(int  n);
int  main()  {
　　　　int  n1,  n2,  i,  flag;
　　　　printf("Enter two positive integers:  ");
　　　　scanf("%d  %d",  &n1,  &n2);
　　　　printf("%d and %d between prime numbers:  ",  n1,  n2);
　　　　for  (i  =  n1　+　1;  i  <  n2;　++i)  {
　　　　　　　　//　If i is a prime number, flag is equal to1
　　　　　　　　flag  =  checkPrimeNumber(i);
　　　　　　　　if  (flag  ==　1)
　　　　　　　　　　　　printf("%d  ",  i);
　　　　}
　　　　return 0;
}
//User-defined function to check prime number
int  checkPrimeNumber(int  n)  {
　　　　int  j,  flag  =　1;
　　　　for  (j  =　2;  j  <=  n　/　2;　++j) {}}
　　　　　　　　if (n % j == 0) {
　　　　　　　　　　　　flag = 0;
　　　　　　　　　　　　break;
　　　　　　　　}
　　　　}
　　　　return flag;
}

Output Result

Enter two positive integers:　12
30
13and3Prime numbers between:　13　17　19　23　29

If the user first enters a larger number, the program will not work properly. To solve this problem, you need to swap the numbers first.

Comprehensive Collection of C Programming Examples