Knowing the place value
The rightmost column is the ones column, the next adjacent one on the left is the tens column, the following adjacent one to the left is the hundreds column, and so on. Adding to it, floating point calculations can be done by designating the space between two columns as the decimal point. Here, all the rows to the right of that space represent the fractional portion while all the rows to the left represent the whole number.
The conventional finger technique is paramount in achieving proficiency on the abacus. The thumb, index finger along with the middle finger are used to manipulate the beads.The thumb is used to move up the beads from the lower deck whereas the index finger is used to move thebead down from the upper deck. In certain calculations, the middle finger is used to move beads in the upper deck.
I did not have a computer until I was 19, But I did have an abacus
Jan Koum, Co-founder & former CEO of WhatsApp