History of computer starts by development of computers. Computer are developed as a result of search for fastest way to calculate.

**1. Abacus: **

The Abacus was the first calculating device of the world, which was first introduced in nearly 3000 BC. The ABACUS is a portable device that consists of beads strung on wires or wooden or bamboo frame.

The ABACUS has two parts divided by middle bar. The above part is known as heaven and the lower part is known as Earth. Each ball of the heaven part takes value 5 and each ball of earth part takes value 1 in calculating.

**2. Napier’s Bone:**

The Napier’s Bone was developed by Scottish mathematician John Napier in 1614 AD. It is very helpful to calculate long number mathematical calculations. With these rods multiplication can be easily done by adding pair of rods. It has 11 rods with sequenced numbers. Napier’s bone are also called Napier’s rod.

**3. Slide Rule: **

The Slide Rule was invented by William Oughtred in 1617 AD. The device was made on the principle of logarithms. This device consists of two graduated scales. One of the scales passes over the other. The scales are devised in such a way that suitable alignment of one scale against the other makes it possible to obtain products, quotients or their function by inspection. The slide rule was used by the engineers till 1970s. This was replaced by calculator. This device can calculate roots, logarithms and trigonometry.

**4. Pascaline:**

The pascaline was developed by French mathematician Blaise Pascal in 1642 AD. Pascaline is the first mechanical calculator. This machine had a capacity of adding or subtracting 8 column numbers up to 999999999. This machine could add and subtract only. This is invented for calculation of tax. This device does perform Addition and Subtraction only. This devices can does multiplication by continue successful addition and division by continue successful division method.

**5. Leibniz’s Calculating Machine:**

In 1671, Gottfried Leibniz’s a German philosopher and mathematician constructed a calculator that was an improvement on Pascal’s invention known as Leibnitz calculator. This machine is also known as Step Reckoner. It can calculate addition, subtraction, multiplication, division and square root etc. This uses process of continue addition and shifting for multiplication and division process.

**6. Difference Engine:**

The Difference Engine was developed by English Mathematician Charles Babbage in 1823. The difference engine was with mechanical memory. Later he design a bigger machine which could compute up to 20 decimal places, called analytical Engine in 1830s. This machine was made to solve differential equations. The analytical engine used axis and gears to computer values and store them and was designed to be a general purpose device that could be used to perform any mathematical operation automatically. The device includes memory, a central processing unit, input/output, and the use of programming language. All these are key elements in today’s computers. That’s why Babbage is often referred to as the father of the modern day Computer.

Lady Augusta ada Lovelace was a mathematician, and a long time supporter of Babbage. Lovelace thought of way to program the machine, so that it would repeat the same set of instructions and carry out instructions, If certain conditions exist. These techniques are still in use today, to make computer programs more efficient. Because of her work, many consider Lovelace, to be the First programmer.

**7. Dr. Herman Hollerith:**

Herman Hollerith designs a system to record census date in 1881. The information stored as holes in cards, which are interpreted by machines with electrical sensors. Hollerith starts at company named Tabulating Machine Company that will eventually become IBM, Which is the most popular computer company of the world. Hollerith proposed a mechanized method to count the census, which was based on punched cards. The cards were punched by a machine called Punched Card Machine or Hollerith’s Tabulaing Machine.

**8. Howard Aiken:**

Next important event was added in the History of computer in 1930. MARK I the first elecromechanical compute was designed by Haward Aiken in 1944 which has the power to support 23 digits. It was built by combining more than 7 lakh separate parts and nearly 500 million wires. It has the power to perform 3 calculations per second. It was presented by Harvard university. It was 57 feet long, 3 ft wide, 8 ft height, weighed 32 tones, 18000 vacuum tubes were used and had almost 7 lakhs 50 thousands parts. It used 500 miles of wire and took almost 4.5 seconds to perform a multiplication tasks.

**9. ENIAC:**

The ENIAC is the acronym of Electronic Numerical Integrator And Calculator. Which was designed by John mauchly and presper Eckert in 1947. It was formed by combining more than 18000 vacuum tubes, more than 70000 resistors, more than 10000 condensers and more than 6000 switches.It was first general purpose computing machine. It was the reprogrammable. It can solve large numerical problems. Hence, it was heralded in the press as a “Giant Brain”.

**10. EDVAC:**

The EDVAC is the acronym of Electronic Discrete Variable Automatic Computer, which was developed by John Mauchley and John Presper Eckert with the help of Goldstine Neumann in 1949. This machine was used to store the data and information as well as the instructions.

**11. EDSAC: **

The EDSAC is the acronym of. Electronic Delay Storage Automatic Calculator (EDSAC) , which was started in 1946 A.D. and loaded first program in 1949 A.D. The EDSAC was the second electronic digital stored-program computer to go into regular service.

12. UNIVAC:

The UNIVAC is the acronym of Universal Automatic Computer which was developed by the company founded by mauchley and Eckert in 1951. It became the first commercially used electronic computer of the world.