# Rust Basics (Rust)

> Variables, mutability, primitive types, functions, expressions, control flow, pattern matching

- 25 interview questions
- Junior
- [Interview Questions: Rust](https://sharpskill.dev/en/technologies/rust/interview-questions.md)

## 1. By default, how are variables declared in Rust?

**Answer**

In Rust, all variables are immutable by default when declared with let. This design promotes safety and concurrency by preventing accidental modifications. To make a variable mutable, explicitly use the mut keyword after let.

## 2. What is the difference between let and const in Rust?

**Answer**

const declares a compile-time constant with mandatory type annotation, while let declares a runtime variable with possible type inference. Constants must have values known at compile time and can be used in compilation contexts like array sizes.

## 3. What is shadowing in Rust?

**Answer**

Shadowing allows redeclaring a variable with the same name using let, creating a new variable that hides the previous one. Unlike mut, shadowing allows changing the variable type. This is useful for transforming a value while keeping the same logical name.

## 22 more questions available

- What is the default signed integer type in Rust?
- What is the difference between isize and i64 in Rust?

Sign up for free: https://sharpskill.dev/en/login

## Other Rust interview topics

- [Ownership & Borrowing](https://sharpskill.dev/en/technologies/rust/interview-questions/ownership-borrowing.md): 22 questions, Junior
- [Structs & Enums](https://sharpskill.dev/en/technologies/rust/interview-questions/structs-enums.md): 20 questions, Junior
- [Error Handling](https://sharpskill.dev/en/technologies/rust/interview-questions/error-handling.md): 18 questions, Junior
- [Collections](https://sharpskill.dev/en/technologies/rust/interview-questions/collections.md): 20 questions, Junior
- [Modules & Packages](https://sharpskill.dev/en/technologies/rust/interview-questions/modules-packages.md): 18 questions, Junior
- [Traits](https://sharpskill.dev/en/technologies/rust/interview-questions/traits.md): 22 questions, Mid-Level
- [Generics](https://sharpskill.dev/en/technologies/rust/interview-questions/generics.md): 20 questions, Mid-Level
- [Lifetimes](https://sharpskill.dev/en/technologies/rust/interview-questions/lifetimes.md): 20 questions, Mid-Level
- [Iterators & Closures](https://sharpskill.dev/en/technologies/rust/interview-questions/iterators-closures.md): 22 questions, Mid-Level
- [Smart Pointers](https://sharpskill.dev/en/technologies/rust/interview-questions/smart-pointers.md): 22 questions, Mid-Level
- [Concurrency Basics](https://sharpskill.dev/en/technologies/rust/interview-questions/concurrency-basics.md): 20 questions, Mid-Level
- [async/await](https://sharpskill.dev/en/technologies/rust/interview-questions/async-await.md): 22 questions, Mid-Level
- [Testing](https://sharpskill.dev/en/technologies/rust/interview-questions/testing.md): 18 questions, Mid-Level
- [Cargo & Ecosystem](https://sharpskill.dev/en/technologies/rust/interview-questions/cargo-ecosystem.md): 18 questions, Mid-Level
- [Pattern Matching](https://sharpskill.dev/en/technologies/rust/interview-questions/pattern-matching.md): 18 questions, Mid-Level
- [Macros](https://sharpskill.dev/en/technologies/rust/interview-questions/macros.md): 20 questions, Mid-Level
- [Serde & Serialization](https://sharpskill.dev/en/technologies/rust/interview-questions/serde-serialization.md): 20 questions, Mid-Level
- [Unsafe Rust](https://sharpskill.dev/en/technologies/rust/interview-questions/unsafe-rust.md): 20 questions, Senior
- [Advanced Traits](https://sharpskill.dev/en/technologies/rust/interview-questions/advanced-traits.md): 22 questions, Senior
- [Advanced Lifetimes](https://sharpskill.dev/en/technologies/rust/interview-questions/advanced-lifetimes.md): 20 questions, Senior
- [Type System](https://sharpskill.dev/en/technologies/rust/interview-questions/type-system.md): 20 questions, Senior
- [Tokio & Async I/O](https://sharpskill.dev/en/technologies/rust/interview-questions/tokio-async.md): 22 questions, Senior
- [Performance Optimization](https://sharpskill.dev/en/technologies/rust/interview-questions/performance-optimization.md): 20 questions, Senior
- [Memory Management](https://sharpskill.dev/en/technologies/rust/interview-questions/memory-management.md): 20 questions, Senior
- [Web Frameworks](https://sharpskill.dev/en/technologies/rust/interview-questions/web-frameworks.md): 22 questions, Senior
- [Database Integration](https://sharpskill.dev/en/technologies/rust/interview-questions/database-integration.md): 20 questions, Senior
- [Rust Design Patterns](https://sharpskill.dev/en/technologies/rust/interview-questions/design-patterns.md): 20 questions, Senior

---

Source: SharpSkill (https://sharpskill.dev), tech interview preparation for your real stack.
HTML version of this page: https://sharpskill.dev/en/technologies/rust/interview-questions/rust-basics