Question and Answers of "C" Language (Module VI) One Year Diploma Course (Part-V)

40. 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.

41. 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.

42. What is pointer to a pointer?


Ans: If a pointer variable points another pointer value. Such a situation is known as a pointer to a pointer.
Example:
int *p1,**p2,v=10;
P1=&v; p2=&p1;
Here p2 is a pointer to a pointer.

43. What is an array of pointers?


Ans: if the elements of an array are addresses, such an array is called an array of pointers.

44. Difference between linker and linkage?


Ans: Linker converts an object code into an executable code by linking together the necessary built in
functions. The form and place of declaration where the variable is declared in a program determine the linkage of variable.

45. Is it possible to have negative index in an array?


Ans: Yes it is possible to index with negative value provided there are data stored in this location. Even if it is illegal to refer to the elements that are out of array bounds, the compiler will not produce error because C has no check on the bounds of an array.

46. Why is it necessary to give the size of an array in an array declaration?


Ans: When an array is declared, the compiler allocates a base address and reserves enough space in
memory for all the elements of the array. The size is required to allocate the required space and hence size must be mentioned.

47. What modular programming?


Ans: If a program is large, it is subdivided into a number of smaller programs that are called modules or subprograms. If a complex problem is solved using more modules, this approach is known as modular programming.

48. 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.

49. What is an argument?


Ans: An argument is an entity used to pass data from the calling to a called function.

50. What are built in functions?


Ans: The functions that are predefined and supplied along with the compiler are known as built-in functions. They are also known as library functions.