Originally, calloc was the function Unix programmers were expected to use by default, since it avoids any sort of intermittent bugs due to your forgetting to in

Originally, calloc was the function Unix programmers were expected to use by default, since it avoids any sort of intermittent bugs due to your forgetting to initialize some field in the data structure you're allocating. But clearing the memory to all zeros took precious time, so if you were an advanced programmer, and knew for a fact that you were going to fill it all in yourself, you could optimize by calling malloc.