5. Charles Babbage

Charles Babbage (26 December 1791 – 18 October 1871) was an English mathematician, philosopher, inventor and mechanical engineer who originated the concept of a programmable computer. Parts of his uncompleted mechanisms are on display in the London Science Museum. In 1991, a perfectly functioning difference engine was constructed from Babbage's original plans. Built to tolerances achievable in the 19th century, the success of the finished engine indicated that Babbage's machine would have worked. Nine years later, the Science Museum completed the printer Babbage had designed for the difference engine, an astonishingly complex device for the 19th century. Considered a "father of the computer" Babbage is credited with inventing the first mechanical computer that eventually led to more complex designs.

6. Augusta Ada King, Countess of Lovelace

Augusta Ada King, Countess of Lovelace (10 December 1815, London – 27 November 1852, Marylebone, London), born Augusta Ada Byron, was the only legitimate child of poet Lord Byron. She is widely known in modern times simply as Ada Lovelace.

She is mainly known for having written a description of Charles Babbage's early mechanical general-purpose computer, the analytical engine. She is today appreciated as the "first programmer" since she was writing programs—that is, encoding an algorithm in a form to be processed by a machine—for a machine that Babbage had not yet built. She also foresaw the capability of computers to go beyond mere calculating or number-crunching while others, including Babbage himself, focused only on these capabilities.

7. Herman Hollerith

Herman Hollerith (February 29, 1860 – November 17, 1929) was a German-American statistician who developed a mechanical tabulator based on punched cards in order to rapidly tabulate statistics from millions of pieces of data. He was the founder of the company that became IBM.

At the urging of John Shaw Billings, Hollerith developed a mechanism to make electrical connections trigger a counter to record information. A key idea was that data could be coded numerically. Hollerith saw that if numbers could be punched in specified locations on a card, in the now familiar rows and columns, then the cards could be counted or sorted mechanically and the data recorded. A description of this system, An Electric Tabulating System (1889), was submitted by Hollerith to Columbia University as his doctoral thesis, and is reprinted in Randell's book. On January 8, 1889, Hollerith was issued U.S. Patent 395,782 claim 2 of which reads: Hollerith had left teaching and begun working for the United States Census Office in the year he filed his first patent application. Titled "Art of Compiling Statistics", it was filed on September 23, 1884; U.S. Patent No. 395782 was granted on January 8, 1889.

Hollerith built machines under contract for the Census Office, which used them to tabulate the 1890 census in only one year. The 1880 census had taken eight years. Hollerith then started his own business in 1896, founding the Tabulating Machine Company. Most of the major census bureaus around the world leased his equipment and purchased his cards, as did major insurance companies. To make his system work, he invented the first automatic card-feed mechanism and the first key punch (i.e. a punch that was operated from a keyboard), which allowed a skilled operator to punch 200–300 cards per hour. He also invented a tabulator. The 1890 Tabulator was hardwired to operate only on 1890 Census cards. A control panel in his 1906 Type I Tabulator allowed it to do different jobs without having to be rebuilt (the first step towards programming).These inventions were the foundation of the modern information processing industry.

In 1911, four corporations, including Hollerith's firm, merged to form the Computing Tabulating Recording Corporation (CTR). Under the presidency of Thomas J. Watson, it was renamed International Business Machines Corporation (IBM) in 1924.