Question:
What is the difference between doing:
ptr = (char **) malloc (MAXELEMS * sizeof(char *));
or:
ptr = (char **) calloc (MAXELEMS, sizeof(char*));When is it a good idea to use calloc and when to use malloc ?
There are two differences:-
- Firstly it is in the number of arguments, malloc() takes a single argument (memory required in bytes), while calloc() needs two arguments.
- Secondly, malloc() does not initialize the memory allocated, while calloc() initializes the allocated memory to ZERO.
calloc() allocates a memory area, the length will be the product of its parameters. calloc fills the memory with ZERO’s and returns a pointer to first byte. If it fails to locate enough space it returns a NULL pointer.
Syntax: ptr_var=(cast_type *)calloc(no_of_blocks , size_of_each_block);
//below is a sample line ptr_var = (type *)calloc(n,s);
malloc() allocates a single block of memory of REQUSTED SIZE and returns a pointer to first byte. If it fails to locate requsted amount of memory it returns a null pointer.
Syntax:ptr_var=(cast_type *)malloc(Size_in_bytes);
//below is a sample line ptr_var = (type *)malloc(n*s);
In a brief summary calloc() zero-initializes the buffer, while malloc() leaves the memory uninitialized.