✅ Embedded C Interview Questions

1. Basics of Embedded C

1. What is Embedded C and how is it different from standard C?
2. Why is C language preferred for embedded systems?
3. What are the features of Embedded C?
4. What are the differences between C and Embedded C?
5. Explain the role of cross compilers in Embedded C.
6. What is the difference between firmware and software?
7. What are the memory types used in embedded systems?
8. Explain the use of the volatile keyword in Embedded C.
9. What is the use of const in Embedded C?
10. What is the difference between #define and const in C?

2. Data Types & Storage

11. What are the basic data types in Embedded C?
12. What is the difference between signed and unsigned integers?
13. Explain fixed-point vs floating-point in embedded systems.
14. What is the difference between int8_t, uint8_t, int16_t, etc.?
15. Why do we prefer fixed-width data types in Embedded C?
16. How does the compiler decide the size of an int?
17. What is endianess (big-endian vs little-endian)?
18. How do you handle endianess issues in Embedded C?
19. What is memory alignment and why is it important?
20. What is padding in structures?

3. Pointers & Memory

21. What is a pointer in C?
22. How are pointers used in embedded systems?
23. What is a null pointer?
24. What is a dangling pointer?
25. What is the difference between pointer to constant and constant pointer?
26. Explain pointer to a function with an example.
27. How are function pointers used in embedded systems (e.g., ISRs)?
28. What is a memory leak? Can it happen in embedded C?
29. How is dynamic memory allocation handled in embedded systems?
30. Why is malloc() often avoided in embedded systems?

4. Preprocessor & Macros

31. What is the role of the preprocessor in C?
32. Difference between #include <file> and #include "file"?
33. What are macros? Give an example.
34. What is the difference between macros and inline functions?
35. Explain conditional compilation in Embedded C.
36. What is the use of #pragma in Embedded C?
37. How are header guards used and why are they needed?
38. What are predefined macros in C?
39. What is the difference between #ifdef and #if defined()?
40. Can you write a macro for swapping two numbers?

5. Embedded C Specific Concepts

41. What is an interrupt?
42. How do you write an Interrupt Service Routine (ISR) in Embedded C?
43. What is the difference between polling and interrupts?
44. What is the role of timers in Embedded C?
45. How is delay implemented in Embedded C?
46. How do you configure I/O ports in Embedded C?
47. What is a watchdog timer?
48. What is memory-mapped I/O?
49. What is the difference between Harvard and Von Neumann architecture?
50. How do you access hardware registers in Embedded C?

6. Embedded C Programming Questions

51. Write a program to toggle an LED connected to a GPIO pin.
52. Write a program to generate a PWM signal.
53. How do you write a delay function using timers?
54. Write a function to reverse a string in C.
55. Write a program to count the number of 1s in a binary number.
56. Write a program to implement a circular buffer in Embedded C.
57. Write code to detect button debounce.
58. How do you write an ISR for a UART receive interrupt?
59. Write a program to check whether a number is power of 2.
60. Implement a simple state machine in C.

7. Optimization & Best Practices

61. What are the different ways to reduce code size in Embedded C?
62. What is loop unrolling?
63. Why is volatile important in Embedded C?
64. How do you avoid race conditions in embedded systems?
65. What is inline assembly in C?
66. Explain memory fragmentation in embedded systems.
67. How do you optimize power consumption in embedded firmware?
68. What is debouncing and how do you handle it in code?
69. Explain the difference between RTOS and bare-metal programming.
70. What is the use of bit-fields in Embedded C?

8. Debugging & Testing

71. How do you debug embedded C code without printf()?
72. What tools are used for embedded system debugging?
73. Explain JTAG and SWD debugging.
74. What is the difference between simulation and emulation?
75. What is boundary scan (JTAG IEEE 1149.1)?
76. How do you measure execution time of a function in Embedded C?
77. What are common causes of hard faults in ARM Cortex MCUs?
78. How do you debug a stack overflow in embedded systems?
79. What is static code analysis?
80. How do you handle error logging in resource-constrained devices?

9. Advanced Embedded C Concepts

81. Explain re-entrant functions.
82. What is mutual exclusion (mutex)?
83. How do you implement semaphores in Embedded C?
84. What is priority inversion and how to solve it?
85. What is the difference between ISR and task in RTOS?
86. How do you implement inter-task communication?
87. What is double buffering in embedded systems?
88. What are DMA controllers and how are they programmed?
89. Explain bootloaders in embedded systems.
90. What is memory protection unit (MPU) in ARM Cortex-M?

10. Frequently Asked HR + Practical Questions

91. Why do you want to work in embedded systems?
92. What projects have you done in Embedded C?
93. How do you keep yourself updated with embedded technologies?
94. What are the biggest challenges in embedded firmware development?
95. What microcontrollers have you worked with (ARM, AVR, PIC, STM32, etc.)?
96. Can you explain your experience with RTOS programming?
97. How do you manage limited memory in embedded systems?
98. Have you worked with UART, SPI, I²C protocols in Embedded C?
99. Describe a debugging issue you faced and how you solved it.
100. Where do you see yourself in embedded development in the next 5 years?