Memory Allocation :

Dynamic memory allocations refers to the method of allocating a block of memory and releasing it when the memory is not required at the time of running the program. A block of memory can be used to store values of simple or subscripted variables and a block of memory can be accessed using a pointer. Following are the functions used in dynamic memory allocation, and these functions are available in the header file <alloc.h> ( "alloc.h is a non-standard header file" ) .

Example :

/* Description: simple memory allocation and after allocation complete free memory */ #include<stdio.h> #include<string.h> main() { char *name; name = malloc(sizeof(char)); if(name==NULL) { printf("allocate not completed."); } else { strcpy(name,"AyaN"); } printf("allocated memory content : %s",name); free(name); getch(); }

Output :

malloc() Function :

malloc() function is used to allocate a single block memory to store values of specific data type. It also assigns the address of the first byte of the allotted space to a pointer.

Syntax :

ptr = (type *)malloc(size);

calloc() Function :

calloc() function is used to allocate memory in multiple block of same size during the program execution. The space alloted is used to store values of an array or structure.

Syntax :

ptr = (type *)calloc(n, m);

realloc() Function :

realloc() function is used to modify or re allocated the memory space which is previously allotted.

Syntax :

ptr = realloc(ptr, size);

free() Function :

free() function is used to release the memory space which is allotted using malloc(), calloc() or realloc() function.

Syntax :

free(ptr);

Dangling pointer / Memory leak :

A dangling pointer is a pointer that does not point to a valid object and consequently may make a program crash or behave oddly. In computer science, a memory leak is a type of resource leak that occurs when a computer program incorrectly manages memory allocations in such a way that memory which is no longer needed is not released. A memory leak may also happen when an object is stored in memory but cannot be accessed by the running code.