Commonly Asked C Programming Interview Questions | Set 4

1. Difference between arrays and linked list?
Ans: An array is a repeated pattern of variables in contiguous storage. A linked list is a set of structures scattered through memory, held together by pointers in each element that point to the next element. With an array, we can (on most architectures) move from one element to the next by adding a fixed constant to the integer value of the pointer. With a linked list, there is a next pointer in each structure which says what element comes next.

2. What are register variables? What are the advantages of using register variables?
Ans: If a variable is declared with a register storage class,it is known as register variable.The register variable is stored in the cpu register instead of main memory.Frequently used variables are declared as register variable as it‘s access time is faster.

3. What is the use of typedef?
Ans: The typedef help in easier modification when the programs are ported to another machine.
A descriptive new name given to the existing data type may be easier to understand the code

4. What is recursion?
Ans: A recursion function is one which calls itself either directly or indirectly it must halt at a definite point to avoid infinite recursion.

5. Differentiate between for loop and a while loop? What are it uses?
Ans: For executing a set of statements fixed number of times we use for loop while when the number of iterations to be performed is not known in advance we use while loop.

6. What the advantages of using Unions?
Ans: When the C compiler is allocating memory for unions it will always reserve enough room for the largest member.

7. What is static memory allocation?
Ans: Compiler allocates memory space for a declared variable. By using the address of operator, the reserved address is obtained and this address is assigned to a pointer variable. This way of assigning pointer value to a pointer variable at compilation time is known as static memory allocation.

8. What is dynamic memory allocation?
Ans: A dynamic memory allocation uses functions such as malloc() or calloc() to get memory dynamically. If these functions are used to get memory dynamically and the values returned by these function are assigned to pointer variables, such a way of allocating memory at run time is known as dynamic memory allocation

9. What is the purpose of realloc?
Ans: It increases or decreases the size of dynamically allocated array. The function realloc (ptr,n) uses two arguments. The first argument ptr is a pointer to a block of memory for which the size is to be altered. The second argument specifies the new size. The size may be increased or decreased. If sufficient space is not available to the old region the function may create a new region.

10. What is a function?
Ans: A large program is subdivided into a number of smaller programs or subprograms. Each subprogram specifies one or more actions to be performed for the larger program. Such sub programs are called functions.