Embedded C Interview Questions and Answers

Ques 1. Explain the difference between a microcontroller and a microprocessor.

A microcontroller integrates a processor with peripheral devices like timers, communication ports, and memory on a single chip. A microprocessor, on the other hand, only includes the CPU.

Ques 2. What is the purpose of a watchdog timer in embedded systems?

A watchdog timer is used to reset the microcontroller if the software hangs or encounters an error, ensuring system reliability.

Ques 3. How does dynamic memory allocation differ in embedded systems compared to desktop applications?

Embedded systems often avoid dynamic memory allocation due to limited resources and potential fragmentation issues.

Ques 4. Explain the role of a linker script in embedded C programming.

A linker script defines the memory layout of an embedded system, specifying the placement of code and data in the target memory.

Ques 5. What is bit masking, and how is it used in embedded C?

Bit masking involves setting or clearing specific bits in a variable to enable or disable certain features, often used in register manipulation.

Example:

#define ENABLE_BIT  (1 << 3)  // Enable bit 3

Ques 6. Explain the concept of a real-time operating system (RTOS) in embedded systems.

An RTOS is designed for time-sensitive applications, ensuring timely execution of tasks and handling events in real-time.

Ques 7. How is interrupt handling implemented in embedded C?

Interrupt handling involves defining ISR (Interrupt Service Routine) functions to respond to specific events or external signals.

Example:

void ISR_Timer() { /* code for timer interrupt */ }

Ques 8. Explain the significance of the 'register' keyword in embedded C.

The 'register' keyword suggests to the compiler that a variable should be stored in a CPU register for faster access.

Example:

register int count;

Ques 9. What is a semaphore in embedded systems?

A semaphore is a synchronization mechanism used to control access to shared resources, preventing race conditions in multitasking environments.

Ques 10. How does a UART communication work in embedded systems?

UART (Universal Asynchronous Receiver/Transmitter) is a popular serial communication protocol in embedded systems, transmitting data bit by bit asynchronously.

Ques 11. Explain the concept of bit fields in C.

Bit fields allow the definition of variables that occupy a specific number of bits in a structure, aiding in efficient memory usage.

Example:

struct Flags { unsigned int flag1:1; unsigned int flag2:1; };

Ques 12. What is the purpose of the 'restrict' keyword in C?

The 'restrict' keyword informs the compiler that a pointer is the only means to access a particular area of memory, helping in optimization.

Example:

void foo(int *restrict ptr);

Ques 13. Explain the concept of reentrant functions in embedded systems.

Reentrant functions can be safely interrupted and resumed, making them suitable for use in multitasking environments where multiple tasks may call the same function simultaneously.

Ques 14. Explain the role of a bootloader in embedded systems.

A bootloader is a program that loads the main application into the microcontroller's memory, typically from external storage like flash or EEPROM.

Ques 15. Explain the concept of polling versus interrupt-driven I/O.

Polling involves repeatedly checking the status of a device, while interrupt-driven I/O relies on hardware interrupts to notify the processor when the device needs attention.

Ques 16. Explain the role of a timer in embedded systems.

Timers are used to measure time intervals, generate time delays, or trigger events at specific intervals, crucial for tasks like real-time control.

Ques 17. What is the purpose of the 'volatile' qualifier in function arguments?

The 'volatile' qualifier in function arguments indicates that the argument may change unexpectedly, even if it appears not to be modified within the function.

Example:

void process_data(volatile int data);

Ques 18. Explain the concept of DMA (Direct Memory Access) in embedded systems.

DMA allows peripherals to directly access the system's memory without involving the CPU, improving data transfer speed and reducing CPU overhead.

Ques 19. What is the purpose of the 'attribute' keyword in GCC (GNU Compiler Collection)?

The 'attribute' keyword is used to specify additional information to the compiler, such as optimizing for size or alignment.

Example:

attribute((packed)) struct PackedStruct { / members */ };

Ques 20. Explain the concept of stack and heap in embedded systems.

The stack is used for local variables and function call management, while the heap is used for dynamic memory allocation, managed by the programmer.