I have two doubt about use of memmove():
memmovemay be faster but it probably will never be slower than your own function for copying data around (it's usually coded in carefully crafted assembly to move stuff around in the most efficient way possible on the current architecture);
arrwill suffice (and, as the length parameter, you should do
sizeof(*arr)*Nwhere N is the number of elements to copy).
By the way, if source and destination and the copy are nonoverlapping
memcpy may be faster.
I want to delete an element from the array and shift left the element of the same array.
int arr[N]; /* ... */ /* Let's say you want to remove the element i (error checking on i omitted) */ memmove(arr+i, arr+i+1, (N-i-1)*sizeof(*arr)); /* or, if you prefer array indexing over pointer arithmetics: */ memmove(&arr[i], &arr[i+1], (N-i-1)*sizeof(*arr));
sizeof(*arr) means "get the size of an element of the array")