This document presents a solved programming assignment for an introductory computer science course. The assignment involves three distinct programs. The first program calculates commission based on retail price and transaction codes (A, B, C), validating inputs and applying different commission rates. The second program calculates student grades based on entered marks, incorporating input validation and if-else statements for grading logic. The third program calculates payable tax based on income, using a chart-based approach and input validation, with a loop to allow multiple calculations. Each program includes input validation, conditional statements, and output displays, demonstrating core programming concepts. The assignment also includes the problem description and pseudo code for the first question.