Programming Languages & Core Development Topics
Programming languages, development fundamentals, coding concepts, and core data structures. Includes syntax, algorithms, memory management at a programming level, asynchronous patterns, and concurrency primitives. Also covers core data manipulation concepts like hashing, collections, error handling, and DOM manipulation for web development. Excludes tool-specific proficiency (see 'Tools, Frameworks & Implementation Proficiency').
Concurrency and Synchronization
Covers the principles and practical techniques for safely coordinating concurrent execution and access to shared resources. Topics include models of concurrency such as threads, processes, interrupt handlers, and tasks in a real time operating system; differences between preemptive and cooperative scheduling; shared data hazards including race conditions and read modify write hazards; critical sections and approaches to protect them including disabling interrupts in embedded contexts and scoped locks. Synchronization primitives and patterns are included: mutexes, binary semaphores, counting semaphores, condition variables, message queues, atomic operations and lock free primitives such as compare and swap. Memory ordering concerns and memory barrier usage on multi core systems are covered, along with priority inversion and priority inheritance. Also addressed are deadlock, livelock, and starvation concepts and avoidance strategies, granularity and performance trade offs of locking, and practical synchronization patterns. Preparation should include identifying and fixing races in code, designing correct concurrent interfaces, and debugging and testing techniques such as stress testing, instrumentation, deterministic replay, race detectors, static analysis, and code review strategies.
Embedded Coding Patterns
Common coding patterns and idioms that are useful in resource constrained firmware. Topics include finite state machine design, event loop and run to completion models, interrupt driven versus polling architectures, timer and debounce handling, buffering strategies such as ring buffers and double buffering, and producer consumer queues. Discuss memory allocation strategies such as static allocation and memory pooling, techniques to avoid fragmentation, and defensive coding practices for interrupt safety and atomicity. Cover trade offs for code size, determinism, and testability, and techniques for testing and simulating hardware behavior.
Advanced Concurrency and Complex Synchronization
Complex multi-threading scenarios: race conditions, deadlocks, priority inversion, live locks. Designing thread-safe code at scale with minimal locking overhead. Understanding synchronization primitives deeply: mutexes, semaphores, atomic operations. Solving real-world concurrency bugs in production. Advanced reactive programming patterns and their performance implications.
Memory Management in Embedded Systems
Covers memory allocation and layout specific to resource constrained and bare metal systems. Topics include memory regions and types such as static flash, read only memory, nonvolatile storage, static random access memory and dynamic random access memory; memory maps, bootloader and firmware placement, and memory mapped input output. Candidates should understand stack versus heap behavior, static versus dynamic allocation patterns, dynamic allocation functions such as malloc and free, memory fragmentation, memory leaks, out of memory handling, and techniques to avoid and mitigate fragmentation. Assess knowledge of memory efficient data structure design, fixed size allocation pools, object pooling, stack allocation techniques, static allocation strategies, wear leveling for nonvolatile storage, memory protection and isolation, and practical profiling and tooling used to measure and optimize memory usage on embedded targets.
Const and Volatile Qualifiers in Embedded Context
Deep understanding of const keyword: const variables, const pointers, pointer-to-const, const functions. Volatile keyword: preventing compiler optimizations for hardware access, volatile variables and pointers. Using volatile for memory-mapped I/O and hardware registers. Understanding why volatile is crucial in embedded systems but often misunderstood.
Concurrency Bugs and Debugging Techniques
Understand common concurrency bugs: race conditions, deadlock, data corruption, and priority inversion. Discuss how to reproduce, diagnose, and fix concurrency issues. Understand challenges of debugging concurrent systems. Discuss defensive programming practices that prevent concurrency bugs.
Bitwise Operations and Bit Manipulation
Covers working with binary representations of integers and performing fundamental bitwise operations including and, or, xor, not, and left and right shifts. Includes techniques for testing setting clearing and toggling individual bits, creating and applying masks, and using bit fields and bit packed structures for compact storage. Addresses endianness and byte order considerations, bit level register manipulation for hardware and embedded systems, and efficient bit algorithms such as population count parity leading and trailing zero detection and sign extension. Encompasses practical uses in protocol parsing flag management performance optimizations and cryptographic primitives including substitution and diffusion concepts. Candidates may be assessed with coding problems that require bit tricks and algorithmic reasoning as well as design questions about data layout and low level interfaces.
Error Handling and Defensive Programming
Covers designing and implementing defensive, fault tolerant code and system behaviors to prevent and mitigate production failures. Topics include input validation and sanitization, null and missing data handling, overflow and boundary protections, exception handling and propagation patterns, clear error reporting and structured logging for observability, graceful degradation and fallback strategies, retry and backoff policies and idempotency for safe retries. Also address concurrency and synchronization concerns, resource and memory management to avoid exhaustion, security related input checks, and how to document and escalate residual risks. Candidates should discuss pragmatic trade offs between robustness and complexity, show concrete defensive checks and assertions, and describe test strategies for error paths including unit tests and integration tests and how monitoring and operational responses tie into robustness.
Arrays, Strings, and Linked Lists Mastery
Foundational data structures: arrays, strings, and linked lists. Covers core operations (insertion, deletion, traversal, searching), pattern usage, edge cases, and time/space complexity analysis, with a focus on practical implementation and common interview-style problems across mainstream programming languages.