Topic 2. Data types, variables, null safety, operations, and control flow constructs

Goal: learn to validate numeric input, use nullable types, conditional expressions, and loops, and justify boundary cases.

Lecture contents

1. Values, types, and conversions — Values, variables, and types · Basic types and number representation · Conversions and overflow
2. Null safety and special types — Nullable types and safe input · Any, Unit, Nothing, and type checking
3. Operations and branching — Arithmetic, equality, and logical operations · if as an expression · when and exhaustive branching
4. Ranges and loops — Ranges and the for loop · while, do-while, and loop termination
5. Contracts and boundary checks — Contracts and boundary checks

Practice and review

• Practice — 3 worked examples with complete code
• Tasks — 30 variants, each with tasks at three difficulty levels
• Summary — conclusions and self-check questions