The abacus below is fully functional. Just click on the beads to move them up or down. The result will appear in the green box. You can also type a number in the white box and press "GO" to see the result on the abacus. Click on the middle bar to move the decimal. If you set 10 or more on any one column, you will get a "pending" message. You can set more than 10 while calculating but the result must always have 9 or less in each column.
The Chinese Abacus is also known in English as the "suanpan". There are two types of beads on the suanpan. Those below the separator beam are sometimes called "earth" beads and each have a value of one. Those above the beam are sometimes called "heaven" beads and each have a value of five.
Numbers are "set" on the suanpan just like Western numbers, with the "ones" digit at the far right, the "tens" digit to the left and so on. If the number has a decimal, then the "ones" position would be somewhere to the left, and the fractional digits would be set to the right of it.
The suanpan is a 2:5 abacus: two heaven beads and five earth beads. The second heaven bead is used for intermediate calculations but it is never set for the result number. Similarly, all five of the earth beads are never set for the result number, but they may all be used for intermediate calculations.
The earliest known written documentation of the Chinese abacus dates to the 2nd century BC, where it was described in a 190 CE book of the Eastern Han Dynasty, "Supplementary Notes on the Art of Figures" written by Xu Yue. However, the exact design of this suanpan is not known. In the famous long scroll Along the River During the Qingming Festival painted by Zhang Zeduan (1085-1145 AD) during the Song Dynasty (960-1297 AD), a suanpan is clearly seen lying beside an account book and doctor's prescriptions on the counter of an apothecary's (Feibao).
By 1200 CE the abacus was commonly used in China, in the 2/5 configuration (2 beads at the top and five at the bottom). Around 1850 a new 1/5 configuration appeared and was widely adopted in Japan. Only China still makes the 2/5 style abacus. In the 1990's the abacus was replaced in schools by calculators, but is still taught in private schools.