Dynamic memory allocation in C - Computer science fundamentals tutorial

Dynamic memory allocation

Dynamic memory allocation 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 sub scripted variable and a block of memory can be accessed using a pointer. Malloc(), calloc(), realloc() are the function used in dynamic memory allocation and this function are available in the header file <alloc.h>. when we have to dynamically allocate memory for variables in our programs then pointers are the only way to go. When we use malloc() for dynamic memory allocation then you need to manage the memory allocated for variables yourself.

malloc():-  malloc() is used to allocate a single memory block memory to store value of specific data type.

Syntax of malloc(): -  pointer variable name=(type *)malloc(size);

Example: -

ptr=(int*)malloc(100);

ptr= (int*) malloc(size of (int));

calloc(): - calloc() function used to allocate memory in multiple blocks of same size during the program execution space allocated is used to store values of an array or structure.

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

n = number of block to be allocated

m = number of bytes in each block of memory. 

realloc(): - realloc() function is used to modified or reallocated the memory space which is previously allotted. This facilate to increase or reduced the allotted space at a late stage in a program.

ptr = realloc()

Free() function: - it is used to release the memory space which allotted using malloc() or calloc() or realloc(). When this function is executed ,allotted blocks of memory are released.

DIFFERENCE BETWEEN STATIC MEMORY ALLOCATION AND DYNAMIC MEMORY ALLOCATION IN C:

DIFFERENCE BETWEEN MALLOC() AND CALLOC() FUNCTIONS IN C: