It is said that the ancient Greeks used something similar to an abacus.
My mother brought an abacus to my daughters the other day.
It is the abacus that I had used more than twenty years ago.
There were a lot of abacus schools when I was a child.
My friends and I have been to this school in my neighborhood.
But fewer people study with abacus since computers are now widely used.
Even now I think that the logic of abacus is more useful for mental calculation than a computer.
I hope that my daughters will be able to use abacus.