QUESTION $1$

$(20$ MARKS$)$

$1\mathrm{.}1$ Explain the role and importance of comments in Python programming. How do comments enhance code readability and maintainability?

$(5$ Marks$)$

$1\mathrm{.}2$ Discuss the concept of variables in Python, contrasting them with constants. Provide examples to illustrate how variables are used differently from constants in a program.

$(5$ Marks$)$

$1\mathrm{.}3$ Detail the significance of different data types in Python. Provide examples of at least three data types and scenarios where each is appropriately used.

$(5$ Marks$)$

$1\mathrm{.}4$ Outline the process of input, processing, and output in Python programs. Describe a real$-$world scenario where this process is crucial, such as data entry and processing in a retail system. $(5$ Marks$)$

QUESTION $2$

$(20$ MARKS$)$

$2\mathrm{.}1$ Explain how Python handles arithmetic operations with an emphasis on operator precedence. Use examples to illustrate how Python evaluates complex arithmetic expressions.

$(5$ Marks$)$

$2\mathrm{.}2$ Describe the use and functionality of escape characters in Python strings. Provide examples of how escape characters can be used in formatting text output, such as in generating a formatted report.

$(5$ Marks$)$

$2\mathrm{.}3$ Discuss the concept of string concatenation and formatting in Python with examples. Explain how these concepts can be applied in generating user$-$friendly messages or data output.

$(5$ Marks$)$

$2\mathrm{.}4$ Define named constants in Python and explain their purpose. Illustrate with an example how using named constants can make a program more readable and maintainable, such as in a scientific calculation.

$(5$ Marks$)$

QUESTION $3$

$(50$ MARKS$)$

$3\mathrm{.}1$ Develop a Python script to simulate a basic user authentication system using if$-$else statements and logical operators. The script should prompt the user for a username and password and validate them against predefined credentials.

$(20$ Marks$)$

$3\mathrm{.}2$ Write a Python program using a while loop to calculate and display the factorial of a user$-$input number. Ensure your program handles invalid inputs gracefully.

$(15$ Marks$)$

$3\mathrm{.}3$ Design a Python script that uses a for loop to print a pattern of numbers or characters. For instance, create a script that prints a pyramid pattern using asterisks $(*)$ based on a user$-$input height.

$(15$ Marks$)$