Python

# How to write a program that displays all prime numbers between 1 and 1003 min read

Here is a simple program in Python that displays all prime numbers between 1 and 100:

This program uses a nested loop to check if a number is prime. The outer loop iterates over the numbers between 2 and 100, and the inner loop checks if the current number is divisible by any number between 2 and itself. If the number is not divisible by any of these numbers, it is a prime number and it is printed to the screen.

The `break` statement is used to exit the inner loop if the number is divisible by a number between 2 and itself. The `else` clause of the outer loop is executed if the `break` statement is not reached, which means that the number is prime.

This program will output the following list of prime numbers:

Here is an alternative solution that uses a different algorithm to check if a number is prime:

This program defines a function `is_prime` that takes a number `n` as an argument and returns `True` if it is prime, and `False` otherwise. The function first checks if the number is 2 or 3, which are both prime. It then checks if the number is 1 or divisible by 2, in which case it returns `False`.

If the number is not 1 or divisible by 2, the function iterates over the odd numbers between 3 and the square root of the number, and checks if the number is divisible by any of these numbers. If the number is not divisible by any of these numbers, it is a prime number and the function returns `True`.

The main loop iterates over the numbers between 1 and 100, and uses the `is_prime` function to check if each number is prime. If a number is prime, it is printed to the screen.

This program will output the same list of prime numbers as the previous solution.

Here is another alternative solution that uses the Sieve of Eratosthenes algorithm to find all prime numbers between 1 and 100:

This program defines a function `sieve` that takes a number `n` as an argument and returns a list of all prime numbers between 1 and `n`.

The function initializes a list `sieve` of `True` values up to `n`, and an empty list `primes` to store the prime numbers. It then iterates over the numbers between 2 and `n`, and checks if the current number is marked as `True` in the `sieve` list. If it is, it is a prime number and it is added to the `primes` list. The function then marks all multiples of the current number as `False` in the `sieve` list, so that they are not considered as prime numbers in the future.

Finally, the function returns the `primes` list.

The main loop calls the `sieve` function with an argument of 100, and prints the returned list of prime numbers.

This program will output the same list of prime numbers as the previous solutions.