a mergesort implementation in c language

mergesort.c

#define ARRMAX 100

void merge(int *A, int i, int j)
{
  int lk, rk, k;
  int mid = (i+j)/2;
  int B[j+1];
  lk = i;
  rk = mid+1;
  k = i;
  while (lk <= mid && rk <= j)
    if (A[lk] <= A[rk])
      B[k++] = A[lk++];
    else
      B[k++] = A[rk++];
  while (lk <= mid)
    B[k++] = A[lk++];
  while (rk <= j)
    B[k++] = A[rk++];
  for (k = i; k <= j; k++)
    A[k] = B[k];
}

void sort(int *A, int i, int j)
{
  if (i >= j) return;
  int mid = (i+j)/2;
  sort(A, i, mid);
  sort(A, mid+1, j);
  merge(A, i, j);
}

int main(int argc, char **argv) {
  int A[ARRMAX];
  int i;
  // only for example purpose
  for (i = 0; i < ARRMAX; i++){
    A[ARRMAX-i] = i;
  }
  sort(A, 0, ARRMAX-1);
  return 0;
}