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
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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