Example to check whether an integer (entered by the user) is a prime number or not using for loop and if...else statement.
A prime number is a positive integer which is divisible only by 1 and itself. For example: 2, 3, 5, 7, 11, 13
Example: Program to Check Prime Number
int n, i, flag = 0;
printf("Enter a positive integer: ");
for(i=2; i<=n/2; ++i)
// condition for nonprime number
printf("%d is a prime number.",n);
printf("%d is not a prime number.",n);
Enter a positive integer: 29
29 is a prime number.
for loop terminates when the test expression of loop
i <= n/2 is false, the entered number is a prime number. The value of flag is equal to 0 in this case.
If the loop terminates because of
break statement inside the
if statement, the entered number is a nonprime number. The value of flag is 1 in this case.