Q.Check whether a number is positive, negative, or zero.

number = int(input("Enter a number: "))  
if number > 0:  
    print("Number is positive")  
elif number < 0:  
    print("Number is negative")  
else:  
    print("Number is zero")  

Ask a shopkeeper about the day's accounts and three situations cover everything: money came in, money went out, or the till broke even. Numbers carry the same three-way nature everywhere — a temperature is above zero, below zero, or exactly zero; a bank balance is in credit, overdrawn, or empty. Classifying a number as positive, negative, or zero is one of the first genuinely useful decisions a program learns to make, and it teaches the single most important structure in programming: choosing between paths.

The classification itself rests on plain facts. A number greater than zero is positive; a number less than zero is negative; and zero itself is neither positive nor negative — it is its own category. That third point is the crux. Zero is the boundary between the other two classes, and treating it carelessly is the classic error.

A program performs the classification with conditional statements — the if, elif, and else structure — testing the number against zero:

num = float(input("Enter a number: "))
if num > 0:
    print("The number is positive")
elif num < 0:
    print("The number is negative")
else:
    print("The number is zero")

Follow the logic as the machine does. The first test asks: is the number greater than zero? If yes, it is positive and the remaining tests are skipped entirely. If no, the second test asks: is it less than zero? If yes, negative. If a number fails both tests — not greater than zero, not less than zero — only one value is left standing, and the else branch names it: zero. The three branches are mutually exclusive (no number satisfies two of them) and exhaustive (every number satisfies one), so exactly one message prints, always. …