Aricent Interview Question Software Engineer in Tests
0of 0 votesWhy is malloc preferred over calloc?
There are two differences. First, is in the number of arguments. Malloc() takes a single argument (memory required in bytes), while calloc() needs two arguments (number of variables to allocate memory, size in bytes of a single variable). Secondly, malloc() does not initialize the memory allocated, while calloc() initializes the allocated memory to ZERO.
Here are more opinions and answers from FAQ Farmers:
The difference between malloc and calloc are: 1. malloc() allocates byte of memory, whereas calloc()allocates block of memory.
Calloc(m, n) is essentially equivalent to p = m*malloc(n); memset(p, 0, m * n); The zero fill is all-bits-zero, and does not therefore guarantee useful null pointer values (see section 5 of this list) or floating-point zero values. Free is properly used to free the memory allocated by calloc.
Malloc(s); returns a pointer for enough storage for an object of s bytes. Calloc(n,s); returns a pointer for enough contiguous storage for n objects, each of s bytes. The storage is all initialized to zeros.
Simply, malloc takes a single argument and allocates bytes of memory as per the argument taken during its invocation. Where as calloc takes two aguments, they are the number of variables to be created and the capacity of each vaiable (i.e. the bytes per variable).
This one is false:
I think calloc can allocate and initialize memory, if the asked memory is available contiguously where as malloc can allocate even if the memory is not available contiguously but available at different locations.
A less known difference is that in operating systems with optimistic memory allocation, like Linux, the pointer returned by malloc isn't backed by real memory until the program actually touches it.
calloc does indeed touch the memory (it writes zeroes on it) and thus you'll be sure the OS is backing the allocation with actual RAM (or swap). This is also why it is slower than malloc (not only does it have to zero it, the OS must also find a suitable memory area by possibly swapping out other processes)
and dont depend on setting all bit 0 by calloc because all bit 0 may not represent floating point 0 / NULL so relying on this can make programm non portable .
Timming is fine. but one more concern I think is freedom of use also. that is how you are going to use that memory.
as calloc allocate n blocks of memory each of size b bytes.
so good if we know size of each elements and all elements are of same size.
whether malloc allocates memory of n bytes that we can use in the way we want. we can divide this space to n variable of different size. hence malloc is prefered over calloc.
Calloc has overhead of initializing to 0
- Prakhar January 14, 2009