C Developer Interview Questions
Want to get down to the nitty-gritty of software development with C? This guide is your C compiler. It's packed with interview questions to help you uncover the ideal C Developer. Whether you're exploring their low-level programming skills, C libraries, or system software expertise, these questions are crafted to unveil their mastery of this foundational language.
What's the difference between malloc() and calloc()?
Answer: malloc() allocates memory but doesn't initialize it, while calloc() allocates and initializes memory to zero.
Describe the use of static in a C program.
Answer: The static keyword can be used with variables and functions. For variables, it makes them retain their values between function calls. For functions, it limits their scope to the file where they're defined.
Explain the purpose of a pointer in C.
Answer: A pointer is a variable that stores the memory address of another variable. It's used to work with dynamic memory allocation, arrays, and function pointers, among other things.
What is the difference between char *p and char p[]?
Answer: char *p declares a pointer to a character, while char p[] declares an array of characters. The latter allocates memory for the array, while the former only stores the address of a character.
How do you deal with memory leaks in C?
Answer: Memory leaks can be avoided by using proper resource management. Always free dynamically allocated memory using free(), and ensure all resources are released before the program exits.
What is a segmentation fault, and why does it occur?
Answer: A segmentation fault occurs when a program tries to access a memory location that it's not allowed to access, such as accessing a NULL pointer or writing beyond the bounds of an array.
What is a structure in C, and how is it different from a union?
Answer: A structure is a user-defined data type that groups variables of different data types into a single unit. In contrast, a union is similar but only reserves enough memory to store the largest member.
Explain the const keyword in C.
Answer: const is used to declare constants. It can be applied to variables to make them read-only. It's a good practice to use const when a variable's value should not be modified.
How do you pass arguments by reference in C?
Answer: In C, you can pass arguments by reference using pointers. By passing a pointer to the memory location of the variable, changes made within the function will affect the original variable.
What are function pointers in C?
Answer: Function pointers store the address of functions, allowing dynamic function calls. They are often used for callback mechanisms, like in event-driven programming or sorting algorithms.
How does the sizeof operator work?
Answer: The sizeof operator returns the size, in bytes, of a variable or data type. It's useful for dynamic memory allocation, array manipulation, and ensuring portability of code.
Can you explain the difference between the ++i and i++ increment operators?
Answer: Both increment i by one, but ++i is pre-increment, meaning it increments i and then returns its new value. i++ is post-increment, meaning it returns the current value of i and then increments it.
What is the purpose of the #define preprocessor directive?
Answer: #define is used to create symbolic constants and macros. It's commonly used to define constants that improve code readability and maintainability.
Explain the concept of dynamic memory allocation in C.
Answer: Dynamic memory allocation involves allocating and releasing memory during program execution. It's performed using functions like malloc(), calloc(), and realloc().
How do you open and close a file in C?
Answer: To open a file, you use fopen(), and to close it, you use fclose(). Proper error handling should be implemented when working with files to ensure they're successfully opened and closed.
What is a pointer to a function in C?
Answer: A pointer to a function stores the address of a function. It's used when functions need to be assigned dynamically, like in callback mechanisms, event handling, or creating flexible function dispatch tables.
Describe the significance of the volatile keyword.
Answer: The volatile keyword tells the compiler that a variable's value can be changed by external factors not apparent to the compiler. It prevents the compiler from optimizing out reads or writes to the variable.
How is a NULL pointer different from a void pointer?
Answer: A NULL pointer points to no memory location, indicating an invalid or uninitialized pointer. A void pointer, on the other hand, is a generic pointer that can point to any data type.
What is the purpose of the #include preprocessor directive?
Answer: #include is used to include external header files in a C program. These files often contain function prototypes, constants, and macros that are needed for program compilation.
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