The construction of roman abacus has seven longer and shorter grooves for whole number counting, the former having four beads while the latter has only one. The rightmost two grooves are used for fractional counting.
The abacus was made of a metal sheet and the size was small enough to fit into a shirt pocket, almost like our modern day calculator. This device has helped the basic operation of roman arithmetic and roman numerals.
The computations are made by means of beads which would be slid up and down to indicate the value of each column. The Romans are said to have a flourished economy, and they have discovered the hand abacus. It was almost a copy of the Babylonian abacus but the changes Romans have introduced for decimal system has helped the engineers a lot.
In Rome the hand abacus was used by the engineers, merchants and the tax collectors. The introduction of the decimal system improvised the advanced calculation involved in trigonometry and helped the construction business and the study of astronomy.
In addition to these for the more complicated calculations involved in the roman surveys, they had a reckoning board with unattached strings and pebbles. This has helped in formulating and faster arrival of solution for certain formulas regarding area and circumference.