Final answer:
A program can easily determine if a number entered by a user is positive or negative, using simple conditional statements to check if the number is greater or less than zero, and then printing the result.
Step-by-step explanation:
A program that determines whether a number input by the user is positive or negative can be written in various programming languages. The logic behind the program is quite simple: if the number is greater than zero, it is positive; if it is less than zero, it is negative; and if it is zero, it is neither positive nor negative.
For example, if we choose to write this program in Python, it may look something like this:
number = float(input("Enter a number: "))
if number > 0:
print("The number is positive.")
elif number < 0:
print("The number is negative.")
else:
print("The number is zero.")
The user is prompted to enter a number. The program then checks if the number is greater than, less than, or equal to zero and prints out the appropriate message based on the result.