Prime number program in c using for loopÂ
Here, you will learn how to write prime number program in C to display the prime numbers between two intervals using the for loop.
A prime number is a whole number greater than 1 whose only factors are 1 and itself, like -2, 3, 5, 7, 11, etc. For example, 7 is a prime number because it is only divisible by 1 and 7. On the other hand, 18 is not a prime number because it is divisible by 2, 3, 6, 9, and the number itself.
In the given C program, we have used a for loop to display the prime numbers between two intervals. In this, we have declared a flag variable to check whether the number is prime or not with the help of the for loop. At first, we initialized the flag as 0.
If i is perfectly divisible by j, i is not a prime number. In this case, the flag is set to 1, and the loop is terminated using the break statement. When, the flag is zero, it prints the prime number, and if the flag is one, it exists from the loop. So, if i is a prime number after the loop, the flag will still be 0, and print the number as prime. However, if i is a non-prime number, the flag will be 1.
#include <stdio.h>
int main(){
int num1,num2,i,j,flag;
printf("Enter the two intervals:");
scanf("%d %d",&num1,&num2);
printf("Prime Numbers between %d and %d:",num1,num2);
for(i=num1+1;i<num2;i++){
flag=0;
//checking number is prime or not
for(j=2;j<=i/2;++j){
if(i%j==0){
flag=1;
break;
}
}
if(flag==0)
printf("%d\n",i);
}
return 0;
}
Output of the above code:
Enter the two intervals:23 55
Prime Numbers between 23 and 55:29
31
37
41
43
47
53
Enter the two intervals:50 90
Prime Numbers between 50 and 90:53
59
61
67
71
73
79
83
89
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