what is the difference between malloc and 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:

• Calloc(m, n) is essentially equivalent to p = malloc(m*n); memset(p, 0, m*n); The zero fill is all-bits-zero, and does not therefore guarantee useful null pointer values or floating-point zero values. 'Free' is useable to release the memory allocated by malloc or 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, and calculates their product.