**1. Abacus:**

The abacus was an early tool for mathematical computations. A skilled abacus user can work on addition and subtraction problems at the speed of a calculator. The abacus is still in use today.

**2. Napier Bones:**

John Napier invented logarithms, where the logarithm values were carved on ivory sticks which are now called Napier’s Bones.

**3.** **Slide Rule:**

Napier bones were modified by Edmund Guntur in the year 1620. It consists of a ruler and a sliding piece both marked with logarithmic values. It was further modified by William Oughtred.

**4. Pascal’s calculating machine:**

The first successful mechanical calculator was constructed by Pascal in 1642.

**5. Leibnitz’s Machine: **

It is the modified form of Pascal’s machine.

**6. Charles Babbage’s Machine:**

In 1833, Charles Babbage invented Charles Babbage Machine. He is known as the “Father of Computers”.

**7. Census Machine:**

This machine was devised by Dr. Hermann Hollerith for tabulating the 1980 US. Census.

**8. Jacquard Loom:**

A weaving machine invented by Joseph Marie Jacquard in the beginning of the 19th century.