matrix pointer

Applications Programming
1

Can anyone tell me what the following statements do?
float (tab)[MAXCLASS];
tab=(float ()[MAXCLASS]) calloc(MAXCLASS,
(MAXCLASS+1)*sizeof(float));

2 
/* creates a pointer named tab that points to an array of MAXCLASS items of type float */
float (*tab)[MAXCLASS];

/* 
  allocates memory for MAXCLASS elements each of size (MAXCLASS+1)*sizeof(float) bytes and
  initializes all memory locations to zeros and casts the pointer to the appropriate type
 */
tab=(float (*)[MAXCLASS]) calloc(MAXCLASS, (MAXCLASS+1)*sizeof(float));

The last one allocates too much memory and IMO the calloc should be...

/*
  allocates memory for MAXCLASS elements each of sizeof(float) bytes and sets
  the memory locations to zeros and casts the pointer to the appropriate type
 */
tab=(float (*)[MAXCLASS]) calloc(MAXCLASS, sizeof(float));
3

Forgot to add that though the two statements are equivalent their difference is that this one allocates memory on the stack...

float (*tab)[MAXCLASS];

while the one below allocates memory from the heap...

tab=(float (*)[MAXCLASS]) calloc(MAXCLASS, (MAXCLASS+1)*sizeof(float));

and written as is the heap one uses more memory than the stack one unless written as shown in my previous post.

4

Thanks very much.