Example program to check whether a Number is Prime or Not in C

Example  program for check whether a Number is Prime or Not in C

In this article, we will discuss the concept of the Example  program to check whether a Number is Prime or Not in C programming language

In this post, we are going to learn how to check whether a number is prime or not from the given number using for, while and do-while loop in C language

 

Prime number

The number that can be divided by 1 and itself. it is called prime number

for Example 2,3,5,7,11,13…

To understand this example programs, you should have previous knowledge of following C topics

for loop in C language

while loop in C language

do-while loop in C language

If statements in C  language

 

Check the prime number using for loop

Program 1

This program allows the user to enter a positive number and then it will check the given number is a prime number or not using for loop in C language

 

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int num,i,count=0;

    printf("Enter the positive integer\n");
    scanf("%d",&num);
    for(i=2; i<=num/2; i++){

    //condition for non-prime
    if(num%i==0)
    {
        count=1;
        break;
    }
}

if(num==1){
    printf("you entered %d\n",num);
    printf("%d is neither a prime nor a composite number ",num);
}
else{
        if(count==0){
            printf("you entered %d\n\n",num);
            printf("%d is a prime number ",num);
        }
        else{
             printf("you entered %d\n",num);
             printf("%d is not a prime number ",num);
        }
}
getch();
    return 0;
}

When the above code is executed, it produces the following results

Case 1

Enter the positive integer
1
you entered 1
1 is neither a prime nor a composite number

Case 2

Enter the positive integer
38
you entered 38
38 is not a prime number

Case 3

Enter the positive integer
29
you entered 29
29 is a prime number

 

Program 2

Check the prime number using while loop

This program allows the user to enter a positive number and then it will check the given number is a prime number or not using while loop in C language

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int num,i,count=0;

    printf("Enter the positive integer\n");
    scanf("%d",&num);

    i=2;
    while(i<=num/2){

    //condition for non-prime
    if(num%i==0)
    {
        count=1;
        break;
    }
    i++;
}

if(num==1){
        printf("you entered %d\n",num);
    printf("%d is neither a prime nor a composite number ",num);
}
else{
        if(count==0){
            printf("you entered %d\n\n",num);
            printf("%d is a prime number ",num);
        }
        else{
             printf("you entered %d\n",num);
             printf("%d is not a prime number ",num);
        }
}
getch();
    return 0;
}

 

When the above code is executed, it produces the following results

Case 1

Enter the positive integer 1
you entered 1
1 is neither a prime nor a composite number

 

Case 2

Enter the positive integer
20
you entered 20
20 is not a prime number

 

Case 3

Enter the positive integer
13
you entered 13
13 is a prime number

 

 

Check the prime number using Do-while loop

Program 3

This program allows the user to enter a positive number and then it will check the given number is a prime number or not using the do-while loop in C language

 

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int num,i,count=0;

    printf("Enter the positive integer\n");
    scanf("%d",&num);

    i=2;
    do{

    //condition for non-prime
    if(num%i==0)
    {
        count=1;
        break;
    }
    i++;
}while(i<=num/2);

if(num==1){
        printf("you entered %d\n",num);
    printf("%d is neither a prime nor a composite number ",num);
}
else{
        if(count==0){
            printf("you entered %d\n\n",num);
            printf("%d is a prime number ",num);
        }
        else{
             printf("you entered %d\n",num);
             printf("%d is not a prime number ",num);
        }
}
getch();
    return 0;
}

When the above code is executed, it produces the following results

Case 1

Enter the positive integer 1
you entered 1
1 is neither a prime nor a composite number

 

Case 2

Enter the positive integer
12
you entered 12
12 is not a prime number

 

Case 3

Enter the positive integer
7
you entered 7
7 is a prime number

 

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input-output function in C language

 

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