1. ABACUS

• The history of computer begins with the birth of abacus which is believed to be the first computer. Chinese invented Abacus around 4000 years ago.
• It was a wooden rack which has metal rods with beads mounted on them. The beads were moved by the abacus operator according to some rules to perform arithmetic calculations.
• Abacus is still used in some countries like china, Russia and Japan.

2. NAPIER’S BONES

• It was a manually operated calculating device which was invented by john Napier (1550-1617) by Merchiston.
• In this calculating tool, he used 9 different ivory strips or bones marked with numbers to multiply and divide . So, the tool became known as “Napier’s bones”.
• It was also the first machine to use the decimal point.

3. PASCALINE

• Pascaline is also known as arithmetic machine or adding machine.
• It was invented between 1642 and 1644.
• By a French mathematician philosopher biais Pascal.
• Pascal invented this machine to help his father, a tax accountant .It could only perform addition and subtraction.
• It was wooden box with a series of gears wheels.

4. STEPPED RECKONER OR LEIBNITZ WHEEL

• It was developed by a German mathematician philosopher Gottfried weilhelm heibntz in 1673. He improved Pascal’s invention to develop this machine. It was a digital mechanical calculator which was called the stepped reckoner as instead of gears it was made a fluted drums.

5. DIFFERENT ENGINE

• In the early 1820s.It was designed by Charles Babbage who is known as “Father of modern computer” .It was mechanical computer which could perform simple calculation .It was a steam driven calculating machine designed to solve tables of numbers like logarithm tables.

6. Analytical Engine

• This calculating machine was also developed by Charles Babbage in 1830.It was a mechanical computer that used Punch-cards as inputs. It was capable of solving any mathematical problem and storing information as a permanent memory.

7. DIFFERENTIAL ANALYSER

• It was first electronic computer introduced in the united states in 1930.It was an analog device invented by Vannevar Bush.

This machine has vacuum bush. This machine has Vacuum tubes to switch electrical signals to perform calculations. It could do 25 calculations in few minutes.