In ancient times, people used fingers to perform the calculations such as addition and subtraction. Even today, simple calculations are done on fingers. Soon, mankind realized that it would be easier to do calculations with pebbles as compared to fingers. Consequently, pebbles were used to represent numbers. Before 1935, a computer was a person who performed arithmetic calculations. Between 1935 and 1945 the definition referred to a machine, rather than a person. The modern machine definition is based on von Neumann’s concepts: a device that accepts input, processes data, stores data, and produces output.



The abacus, probably invented in Sumer between 2700 and 2300 BC, is the first computing machine invented by humans, but has no automatically moving parts or gears and only provides an aid to calculation.

The abacus also called a counting frame, is a calculating tool used primarily in parts of Asia for performing arithmetic processes. Today, abaci are often constructed as a bamboo frame with beads sliding on wires, but originally they were beans or stones moved in grooves in sand or on tablets of wood, stone, or metal. Abacus emerged around 5000 years ago in Asia Minor and it is still in use in some parts of the world. The word ‘abacus’ was derived from the Arabic word ‘abaq’, which means ‘dust’. An abacus consists of sliding beads arranged on a rack, which has two parts: upper and lower. The upper part contains two beads and the lower part contains five beads per wire. The numbers are represented by the position of the beads on the rack. For example, in the upper part of the rack, a raised bead denotes 0, whereas a lowered bead denotes digit 5. In the lower part, a raised bead stands for 1 and a lowered bead stands for 0. The arithmetic operations like addition and subtraction can be performed by positioning the beads appropriately.



John Napier (1550-1617), a Scottish mathematician, is mostly known for his invention of logarithms – a device that revolutionized calculations by reducing difficult and tedious multiplication to addition of table entries. In 1614, John Napier, a Scottish mathematician, made a more sophisticated computing machine called the Napier bones. This was a small instrument made of 10 rods on which the multiplication table was engraved. It was made of the strips of ivory bones, and so the name Napier bones. This device enabled multiplication in a fast manner, if one of the numbers was of one digit only. Incidentally, Napier also played a key role in the development of logarithms, which stimulated the invention of slide rule, which substituted the addition of logarithms for multiplication. This was a remarkable invention as it enabled one perform the multiplication and division operations by converting them into simple addition and subtraction operations.



Slide rule is a manual device used for calculation that consists in its simple form of a ruler and a movable middle piece which are graduated with similar logarithmic scales. The slide rule is used primarily for multiplication and division, and also for functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction. The invention of logarithms influenced the development of another famous invention known as slide rule. In 1620 AD, the first slide rule came into existence. It was jointly devised by two British mathematicians, Edmund Gunter and William Oughtred. It was based on the principle that actual distances from the starting point of the rule is directly proportional to the logarithm of the numbers printed on the rule. The slide rule is embodied by two sets of scales that are joined together, with a marginal space between them. This space is enough for the free movement of the slide in the groove of the rule. The suitable alliance of two scales enabled the slide rule to perform multiplication and division by a method of addition and subtraction.



In 1623, Wilhelm Schickard invented the ‘calculating clock’, which could add and subtract, and indicated the overflow by ringing a bell. Subsequently, it helped in the evolution of Pascaline. Blaise Pascal, a French mathematician, scientist and philosopher, invented the mechanical calculator in 1642. He conceived the idea while trying to help his father who had been assigned the task of reorganizing the tax revenues of the French province of Upper Normandy; first called Arithmetic Machine, Pascal’s Calculator and later Pascaline, it could add and subtract two numbers directly and multiply and divide by repetition. It had a complex arrangement of wheels, gears and windows for displaying numbers. It was operated by a series of dials attached to the wheels with each wheel having 10 segments (numbered from zero to nine) on its circumference. When a wheel made a complete turn, the wheel on its left advanced by one segment. Indicators above the dial displayed the correct answer. However, the usage of this device was limited to addition and subtraction only.



Gottfried Wilhem von Leibniz, a German mathematician started to work on his own calculator after Pascal’s death. He first tried to build a machine that could multiply automatically while sitting on top of the Pascaline, assuming (wrongly) that all the dials on Pascal’s calculator could be operated at the same time. Even though it could not be done, this was the first time that a pinwheel was described and used in the drawings of a calculator.

He then devised a competing design, the Stepped Reckoner which was meant to perform additions, subtractions and multiplications automatically and division under operator control; Leibniz struggled for forty years to perfect this design and produced two machines,one in 1694 and one in 1706. Only the machine built in 1694 is known to exist; it was rediscovered at the end of the 19th century, having spent 250 years forgotten in an attic in the University of Gottingen. In 1694, von Leibniz, extended the Pascal’s design to perform multiplication and division and to find square root. This machine is known as Stepped Reckoner. It was the first mass-produced calculating device, which was designed to perform multiplication by repeated additions. Like its predecessor, Leibniz’s mechanical multiplier worked by a system of gears and dials. The only problem with this device was that it lacked mechanical precision in its construction and was not very reliable.



In 1801, Joseph Marie Jacquard, a French textile weaver, invented a power loom with an automatic card reader. It is based on earlier inventions by the Frenchmen Basile Bouchon (1725), Jean Baptiste Falcon (1728) and Jacques Vaucanson (1740).

This power loom used a series of cards with holes punched at different positions. To automate the weaving process, these cards were placed between the needles and the thread, thereby creating different patterns. This idea of using punched cards to communicate with machines was an important step in the development of computers. The presence or absence of a hole in a punched card represented the two digits of the binary system, which is the base for all modern digital computers.




In 1822, Charles Babbage, a professor of mathematics, devised a calculating machine known as difference engine, which could be used to mechanically generate mathematical tables. A difference engine is an automatic mechanical calculator designed to tabulate polynomial functions. The name derives from the method of divided differences, a way to interpolate or tabulate functions by using a small set of polynomial coefficients. Both logarithmic and trigonometric functions, functions commonly used by both navigators and scientists, can be approximated by polynomials, so a difference engine can compute many useful sets of numbers.

The difference engine can be viewed as a huge complex abacus. It was intended to solve differential equations as well. However, Babbage never made a fully functional difference engine and in 1833, he quit working on this machine to concentrate on the analytical engine.



The Analytical Engine was a proposed mechanical general-purpose computer designed by English mathematician Charles Babbage.

It was first described in 1837 as the successor to Babbage’s Difference engine, a design for a mechanical computer. The Analytical Engine incorporated an arithmetic logic unit, control flow in the form of conditional branching and loops, and integrated memory, making it the first design for a general-purpose computer that could be described in modern terms as Turing – complete.

Babbage’s innovation in the design of the analytical engine made it possible to test the sign of a computed number and take one course of action if the sign was positive and another if the sign was negative. Babbage also designed this device to advance or reverse the flow of punched cards to permit branching to any desired instruction within a program. This was the fundamental difference between the analytical engine and the difference engine.

Lady Ada Lovelace helped him in the development of the analytical engine. She not only helped Babbage with financial aid, but also, being a good mathematician, wrote articles and programs for the proposed machine. Due to her contributions, she is known as the ‘first programmer’. However, Babbage never completed the analytical engine, but his proposal for this device reviewed the basic elements of modern computer such as input/output, storage, processor and control unit.



The tabulating machine was an electromechanical machine designed to assist in summarizing information and, later, accounting. Invented by Herman Hollerith, the machine was developed to help process data for the 1890 U.S. Census. It spawned a class of machines, known as unit record equipment, and the data processing industry.

Hollerith used punched cards with round holes, 12 rows and 24 columns. His tabulator used electromechanical relays (and solenoids) to increment mechanical counters. A set of spring-loaded wires were suspended over the card reader. The card sat over pools of mercury, pools corresponding to the possible hole positions in the card. When the wires were pressed onto the card, punched holes allowed wires to dip into the mercury pools, making an electrical contact that could be used for counting, sorting, and setting off a bell to let the operator know the card had been read. The tabulator had 40 counters, each with a dial divided into 100 divisions, with two indicator hands; one which stepped one unit with each counting pulse, the other which advanced one unit every time the other dial made a complete revolution.

This electronic machine was able to read the information on the cards and process it electronically. It consisted of a tabulator, a sorter with compartments electronically controlled by the tabulator’s counter and a device used to punch data onto cards. This tabulator could read the presence or absence of holes in the cards by using spring-mounted nails that passed through the holes to make electrical connections. In 1896, Hollerith founded the Tabulating Machine Company, which was later named as IBM (International Business Machines).



As a bank clerk in Auburn, New York, William Seward Burroughs (1857-1898) became convinced that banks needed a machine that would add figures accurately and print entries and sums. When poor health forced Burroughs to leave the bank in 1882, he resolved to invent an adding machine. He went to St. Louis, took a job in a machine shop, and began tinkering. By 1891, he had several patents and an adding machine sufficiently reliable for use in banks. It was sold by a firm called /American/ Arithmometer Company, later renamed Burroughs.

To use a Burrough’s adding machine, an operator first pushed down the digits on the keyboard for the number to be added. Pulling the crank forward caused the entry to print. Releasing the crank added the number to those already entered. Adding took place through a system of toothed segments and gears. In the early machine shown, the only way to see the sum was to print it out. Later on Burrough machines, a row of numeral dials displayed the running total.

Unfortunately for Burroughs, ill health plagued him in the 1890s, he was forced to retire in 1897, and he died the next year. Burrough’s Corporation would remain an active manufacturer of calculating machines and then computers. In the 1980s it merged with Sperry Univac to form Unisy.



In the process of the development of automating computers, many scientists and engineers have made significant contributions.

  1. In 1904, Sir John Ambrose Fleming worked to develop the first thermionic valve, which is also known as vacuum tube. Thermionic valves were based on Thomas Edison’s ‘Edison effect’ of light bulbs. The first light bulbs were very short-lived and were prone to darken. This darkening was termed as Edison effect. Sir John Ambrose Fleming worked to develop the first rectifier and in 1904, he developed thermionic valves. Fleming named the device ‘a valve’ because it allowed electrical currents to pass only in one direction. Since this is a two-element vacuum tube, it was also called as diode. These diodes were the cornerstone of the first-generation computers.
  2. In 1906, Lee de Forest, an American inventor, introduced a third electrode into the diode (vacuum tube). The resulting triode could be used both as an amplifier and a switch and its ability to act as a switch created a tremendous impact on digital computing.
  3. In 1931, Vannevar Bush, an American electrical engineer, built the differential analyser to solve differential equations. Nevertheless, the machine was cumbersome because this device used drive belts, shafts and gears to measure movements and distances.
  4. In 1938, Claude Shannon, a student at MIT, recognized the connection between the electronic circuits and the Boolean algebra. He transferred the two logic states to electronic circuits by assigning different voltage levels to each state. Shannon also provided electronic engineers with the mathematical tool they needed to design digital electronic circuits. These techniques remain the cornerstone of digital electronic design to this day.
  5. 1939 -1942 – Atanasoff Berry Computer – built at Iowa State by Prof. John V. Atanasoff and graduate student Clifford Berry. Represented several “firsts” in computing, including a binary system of arithmetic, parallel processing, regenerative memory, separation of memory and computing functions, and more. Weighed 750 lbs. and had a memory storage of 3,000 bits (0.4K). Recorded numbers by scorching marks into cards as it worked through a problem.
  6. 1940s – Colossus – a vacuum tube computing machine which broke Hitler’s codes during World War II (WW II). It was instrumental in helping Turing break the German’s codes during WW II to turn the tide of the war. In the summer of 1939, a small group of scholars became codebreakers, working at Bletchley Part in England. This group of pioneering codebreakers helped shorten the war and changed the course of history.

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