I applied for a WLAN Firmware Developer position.

To be called for an interview, I had to clear an online coding test.

Practicing HackerRank problems was sufficient for passing the test.

OS and C concepts are mandatory for the interview. For WLAN, basics of WiFi may be needed.

Description of projects from college or previous industry experience.

What problems you faced and how you solved them.

C code for adding and deleting nodes in a linked list. Modify the same for a circular linked list.

Differences between arrays and Linked Lists, and point out their advantages and disadvantages.

There is a mod 60 hardware counter that generates an overflow interrupt. I can access the count value register of the counter. Write a program to show the time in Hour, Minute, and Seconds to the user.

Write a program to find the number of digits in the decimal representation of a user-input number.

Let's suppose the Modulus operation (%) is not supported by a system. Write a program to implement the modulus operation.

Write a program to print a number in reverse in decimal format.

Reverse a string without using a temporary variable for swapping.

Demonstrate the use of function pointers.

Write a program to toggle an arbitrary bit of a number without modifying other bits.

Count the number of set bits in a 32-bit number. Modify the program so that the loop can't run more than the number of set bits in that number.

Find repeated characters in a string.

Memory organization in C.

How malloc() allocates memory from the heap internally.

How a task is preempted when an interrupt occurs. Where the status, etc., of the task is stored.

What are the different task queuing types in an RTOS?

Interrupt handling in an RTOS. How it is divided into a Top half and a Bottom half. What is the advantage?

What is the use of a volatile variable in C?

What is priority inversion in an OS, how it happens, and how to avoid it.

Static and extern types of variables in C. Where are they allocated? Scope and lifetime. Can we use them in another C file?

sizeof(int), sizeof(int*), sizeof(int**). Write your own sizeof() function.

How much memory is actually allocated in malloc(0)? Why is it non-zero? Why does malloc allocate more memory than asked for?

Which one will behave how in which OS, which one crashes faster, and why?

while(1) int p = (int)malloc(10);

while(1){ int p = (int)malloc(10); memset(p, 1, 10); }

WLAN frame exchange basics: How an AP associates with an STA.