C Language Memory Allocation Functions for B.C.A., B.Sc.(IT) and P.G.D.C.A. Students

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Prepared By : Uday Shah (HOT- IT)
Contact No : 7600044051
Email : rupareleducation@gmail.com

Dynamic memory allocation in C

The concept of dynamic memory allocation in c language enables the C programmer to allocate memory at runtime. Dynamic memory allocation in c language is possible by 4 functions of stdlib.h header file.

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

• malloc() : allocates single block of requested memory.

• calloc()  : allocates multiple block of requested memory.

• realloc() : reallocates the memory occupied by malloc() or calloc() functions.

• free()  : frees the dynamically allocated memory

malloc() :

• The malloc() function allocates single block of requested memory.
• It doesn't initialize memory at execution time, so it has garbage value initially.
• It returns NULL if memory is not sufficient.
• The syntax of malloc() function is given below:

ptr=(cast-type*)malloc(byte-size) 

calloc() :

• The calloc() function allocates multiple block of requested memory.
• It initially initialize all bytes to zero.
• It returns NULL if memory is not sufficient.
• The syntax of calloc() function is given below:

ptr=(cast-type*)calloc(number, byte-size)

realloc() :

• If memory is not sufficient for malloc() or calloc(), you can reallocate the memory by realloc() function. In short, it changes the memory size.
• Let's see the syntax of realloc() function.

ptr=realloc(ptr, new-size) 

free() :

• The memory occupied by malloc() or calloc() functions must be released by calling free() function. Otherwise, it will consume memory until program exit.
• Let's see the syntax of free() function.

free(ptr)  

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