**Mechanical Counting and Calculating Devices**

As a result of the disadvantages of the early counting devices, more advanced mechanical counting and calculating devices were invented. Some of these devices are;

- Abacus (Chinese)
- Napier’s Bone (John Napier)
- Slide Rule (William Oughtred)

**THE ABACUS **

The Abacus is made up of beads threaded on iron rods. The iron rods are fixed to a rectangular wooden frame. It is used for addition and subtraction only. It could not carry out complex mathematics. The Abacus was early used for arithmetic tasks, it was developed in China about 5000 years ago. It was successful that its use spread from china to many other countries.

**NAPIER’S BONE**

After the Abacus, the next significant development was the Napier’s Bone made by John Napier in the year 1617. John Napier was a mathematician, physicist, and astronomer from Scotland. His most important achievement was the discoverery of logarithms. He also made the use of the decimal point in arithmetic and mathematics common. Napier’s bone is a manually-operated calculating device for calculation of products and quotients of numbers.

Using the multiplication tables in the rods, multiplication can be reduced to addition and division to subtractions. More advanced use of the rods can even extract square roots. Napier’s bone is not the same as logarithms, with which Napier’s name is also associated. The complete device usually includes a base board with a rim; the user places Napier’s rods inside the rim to carry out multiplication or division. The board’s left edge is divided into 9 squares, holding the numbers 1 to 9. The Napier’s rod is made up of of strips of wood, metal or heavy cardboard. Napier’s bone is three-dimensional, square in cross section, with four different rods embedded on each one.

**SLIDE RULE**

The slide Rule which is also called the **slip-stick **in the United States of America was invented around 1620-1630 shortly after John Napier’s publication of the concept of logarithms. It is a mechanical analogue computer. The slide rule is used mostly for multiplication, division, and also for functions as roots, algorithms and trigonometry, **but is not normally used for addition or subtraction.**

Slide rules come in different range of styles and generally appear in a straight or circular form with a standardized set of markings (scales) essential to performing mathematical operations.

The use of slide rule continued to grow through the 1950s and 1960s even as digital computing devices were being gradually introduced.

** **

**EVALUATION**

- Mention two examples of mechanical counting/calculating devices
- Who invented the Speeding clock?
- To perform Multiplication on the Speeding clock, ………… was added to it
- The slide rule was invented by …………..
- Another name for Slide Rule is ……………

**See also**

HISTORICAL DEVELOPMENT OF COMPUTERS

MODERN METHODS OF TRANSMITTING INFORMATION

ANCIENT METHODS OF TRANSMITTING INFORMATION

HEALTH CONCERNS OF COMPUTER USE