Abacus is a centuries old rectangular wooden instrument with beads on rods in a frame used to do calculations based on the decimal system.It has vertical rods with sliding beads and a fixed bar across the rods.
Soroban abacus has gone through an evolution, Where in 15th Century it had having two beads in the upper part and five beads in lower part similar to Chinese abacus. Later in 1850 a revised design was introduced removing a bead from the top level and making it one bead in the upper part and five beads in lower part. The current soroban design we are using in today’s world was introduced in 1930, with one bead in upper part and four beads in lower part. Lets do abacus uses a modern 17 bead Japanese soroban with with 5 beads in each bar, 1 above the bar and 4 below. We train our students following "work from left to right" technique.