linux - What is the need for having "nmem" and "size" parameters in C functions?

I've noticed this with many C functions calls particularly ones that deal with memory or file operations, but not all of them use both parameters. For instance malloc is passed one parameter, the size in bytes of the memory space needed. Calloc on the other hand is passed two parameters, the size in bytes of an element and the number of elements (size and nmem). There are other functions that use these size and nmem parameters as well.

Essentially the calloc call would allocate the same amount of memory as calling malloc(nmemsize) so all that's really happening is the asterisk () is replaced with a comma (,). At least this is all I can tell from the higher level that I am working at. I don't see a difference from calling calloc(1, nmemsize), calloc(nmemsize, 1), or calloc(nmem, size).

Is there something actually happening at a lower level that makes calling for instance calloc(1, nmem*size) fundamentally different from calloc(nmem, size)?

Edit: I know the functional difference between calloc and malloc. I'm interested in why there are differences in the parameters. There are other functions that use 2 size parameters for the total size (fread, fwrite, etc). I'm not concerned with the specific functions but rather why there are two parameters for the total size used in the function when essentially the total size becomes the two parameters multiplied together. I find most of the time when I use these functions I use the size that I need in the "size" parameter and a '1' for the "nmem" (sometimes "count" etc.) parameter.