C Programming Interview Questions Part 49: What is a state machine and how is it implemented in C?

C Programming Interview Questions Part 49
What is a state machine and how is it implemented in C?

A state machine is a programming model used to design systems with a finite number of distinct states and well-defined transitions between those states based on events or conditions. It is commonly used in embedded systems, protocols, game development, and UI control.

There are two types:
1. Finite State Machine (FSM) – where the number of states is finite.
2. Mealy and Moore Machines – based on how outputs depend on inputs and states.

Implementation in C is typically done in two ways:
1. Using switch-case and enums
• Define all states using an enum.
• Use a loop with a switch-case to handle each state and transition logic.
2. Using function pointers and state tables
• Create an array of state functions (handlers).
• Transitions are managed using lookup tables or logic embedded in state functions.
• Offers better modularity and scalability.

This approach keeps the code organized, especially for complex or event-driven applications.

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