What is a prime number ?

Integer Greater than 1

Its only factor is 1 and itself.

It should not be divisible ( with reminder equal to 0 ) by any number less than it and greater than 1.

We will be using fmod() or % operator to get reminder of any division.

First we will use while loop to display all the number between 2 and our given number ( 100 ).

```
while (i<=my_num){
// statements
}
```

We will use one flag and set the value to 0 at the beginning of each loop.
```
while (i<=my_num){
flag=0;
}
```

By using a for loop we will divide each number by all number starting from 2 and ending one less than the number.
```
for(j=2;j<=i-1;j++){
if(i % j == 0 ){
flag=1;
break;
}
}
```

At any point inside the for loop if the reminder of division became 0 then we will exit the for loop and set the flag to 1 . That will indicate that the number is not a prime number.
Before starting the next loop we will reset the flag to 0 again as shown above. We used one if condition to check the flag value and display the message if it is equal to 0;

Here is the complete code

```
#include<stdio.h>
#include<string.h>
int main()
{
int my_num=100;
int i=2,j;
int flag=0;
while (i<=my_num){
flag=0;
for(j=2;j<=i-1;j++){
if(i % j == 0 ){
flag=1;
break;
}
} // end of for loop
if(flag==0){
printf( " %d is a prime number \n",i);
}
i++;
} // end of while loop
return 0;
}
```

Numbers other than Prime numbers will have factors , we can list the factors of a given number.
Factors of a input number

This article is written by **plus2net.com** team.

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