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An adapted abacus, invented by Tim Cranmer, and called a Cranmer abacus is commonly used by visually impaired users. A piece of soft fabric or rubber is placed behind the beads, keeping them in place while the users manipulate them.
The Late Roman hand abacus shown here as a reconstruction contains seven longer and seven shorter grooves used for whole number counting, the former having up to four beads in each, and the latter having just one. The rightmost two grooves were for fractional counting. The abacus was made of a metal plate where the beads ran in slots.
The book describes methods of doing calculations without aid of an abacus, and as Ore (1948) confirms, for centuries after its publication the algorismists (followers of the style of calculation demonstrated in Liber Abaci) remained in conflict with the abacists (traditionalists who continued to use the abacus in conjunction with Roman numerals).
The first abacus pictured below (fig. 5) is decorated with simple mouldings and ornaments, common during the 12th century, in Île-de-France, Normandy, Champagne, and Burgundy regions, and from the choir of Vézelay Abbey (fig. 6). Figure 7 shows a circular abacus used at windows in the side chapels of Notre Dame de Paris. Towards the end of ...
The abacus was early used for arithmetic tasks. What we now call the Roman abacus was used in Babylonia as early as c. 2700 –2300 BC. Since then, many other forms of reckoning boards or tables have been invented.
In c. 1050 –771 BC, the south-pointing chariot was invented in ancient China. It was the first known geared mechanism to use a differential gear, which was later used in analog computers. The Chinese also invented a more sophisticated abacus from around the 2nd century BC known as the Chinese abacus. [citation needed]
c. 1000 — Pope Sylvester II introduces the abacus using the Hindu–Arabic numeral system to Europe. 1030 — Ali Ahmad Nasawi writes a treatise on the decimal and sexagesimal number systems. His arithmetic explains the division of fractions and the extraction of square and cubic roots (square root of 57,342; cubic root of 3, 652, 296) in an ...
Zhusuan was an abacus invented in China at the end of the 2nd century CE and reached its peak during the period from the 13th to the 16th century CE. In the 13th century, Guo Shoujing (郭守敬) used Zhusuan to calculate the length of each orbital year and found it to be 365.2425 days.