CALCULATOR named Later to Mr Processor ‘the computer’ about Abacus Abu (continuing): "Adding on abacus was child’s play, but subtracting is even easier. For adding, we move beads towards the middle bar or the beam; and, to subtract, we move beads away from the middle bar or the beam."

"If you want to subtract 7 from 11 (do 11-7), you will have to, first, represent 11. For representing 11, we have to, first, move up to the middle bar one 1-bead in the 10’s column. To this 10, we’ll have to add 1 by moving up to the middle bar one 1-bead in the 1’s column, to make the total 11."

"We’ll do 11-7 as 11-10+3; as the two things are the same. After we have represented 11 on the middle bar, to subtract 10 from it, we’ll have to move away from the middle bar (bring down) the one 1-bead in the 10’s column. To add 3 to it, move up to the middle bar three 1-beads in the 1’s column. Now that the operation 11-10+3 or 11-7 is over, read the answer from the middle bar. One the beam, there are four 1-beads in the 1’s column. The answer is 4 (which is 11-7=4).

"Mr Processor: "Don’t bore me with elementary mathematics; my grandfather could do that." Later: "Consider abacus to be the grandfather of analysing engine, that was your grandfather. Does that take out false pride from your mind or do you want to play more games?" (To be continued; write at The Tribune or adityarishi99@yahoo.co.in)