Why do we need dynamic memory allocation techniques? Explain the functions available for allocating memory dynamically.

DYNAMIC MEMORY ALLOCATION----

•  It refers to performing manual management for dynamic memory allocation using standard library functions such as malloc, realoc, calloc and free.
• The size of array initially declared can be sometimes insufficient or sometimes more than required but dynamic memory allocation allows a program to obtain more memory space, while running or to release space when not required.

FUNCTIONS OF DYNAMIC MEMORY ALLOCATION----

• There are four standard library functions under “stdlib.h” for dynamic memory allocation. 

1. malloc()
2. calloc()
3. realloc()
4. free()             

=>   malloc() – It allocates requested size of bytes and returns a pointer first byte of allocated space.

                      Syntax : ptr=(data_type *)malloc(bysize);

                      Ex : (int*)malloc(100*sizeof(int)) 

=>   calloc() – Allocates spaces for array elements, initializes to zero and then returns a pointer to memory.

                      Syntax : ptr=(data_type*)calloc(n,element_size);

                      Ex : ptr=(float*)calloc(25,sizeof(float))

=>   realloc() – Changes the size of the previously allocated space according to the requirement.

                      Syntax : ptr=realloc(ptr,newsize);

=>   free() – It deallocates the previously allocated space.

                     Syntax – free(ptr);