The First Mechanical Computer

Charles Babbage, a mathematics professor in Cambridge, England, is considered by many to be the father of computers because of his two great inventions—each a different type of mechanical computing engine. The Difference Engine, as he called it, was conceived in 1812 and solved polynomial equations by the method of differences.

By 1822, he had built a small working model of his Difference Engine for demonstration purposes. With financial help from the British government, Babbage started construction of a full-scale model in 1823. It was intended to be steam-powered and fully automatic, and it would even print the resulting tables.

Babbage continued work on it for 10 years, but by 1833 he had lost interest because he now had an idea for an even better machine, something he described as a general-purpose, fully program-controlled, automatic mechanical digital computer. Babbage called his new machine an Analytical Engine.

The plans for the Analytical Engine specified a parallel decimal computer operating on numbers (words) of 50 decimal digits and with a storage capacity (memory) of 1,000 such numbers.

Built-in operations were to include everything that a modern general-purpose computer would need, even the all-important conditional function, which would allow instructions to be executed in an order depending on certain conditions, not just in numerical sequence.

In modern computer languages, this conditional capability is manifested in the IF statement. The Analytical Engine was also intended to use punched cards, which would control or program the machine. The machine was to operate automatically by steam power and would require only one attendant.

The Analytical Engine is regarded as the first real predecessor to a modern computer because it had all the elements of what is considered a computer today. These included

  • An input device. Using an idea similar to the looms used in textile mills at the time, a form of punched cards supplied the input.
  • A control unit. A barrel-shaped section with many slats and studs was used to control or program the processor.
  • A processor (or calculator). A computing engine containing hundreds of axles and thousands of gears about 10 feet tall.
  • Storage. A unit containing more axles and gears that could hold 1,000 50-digit numbers.
  • An output device. Plates designed to fit in a printing press that were used to print the final results.

Alas, this potential first computer was never actually completed because of the problems in machining all the precision gears and mechanisms required. The tooling of the day was simply not good enough. An interesting side note is that the punched card idea first proposed by Babbage finally came to fruition in 1890.

That year a competition was held for a better method to tabulate the U.S. Census information, and Herman Hollerith, a Census Department employee, came up with the idea for punched cards. Without these cards, department employees had estimated the census data would take years to tabulate; with these cards they were able to finish in about six weeks.

Hollerith went on to found the Tabulating Machine Company, which later became known as IBM. IBM and other companies at the time developed a series of improved punch-card systems. These systems were constructed of electromechanical devices, such as relays and motors.

Such systems included features to automatically feed in a specified number of cards from a "read-in" station; perform operations, such as addition, multiplication, and sorting; and feed out cards punched with results. These punched-card computing machines could process 50–250 cards per minute, with each card holding up to 80-digit numbers.

The punched cards not only provided a means of input and output, but they also served as a form of memory storage. Punched-card machines did the bulk of the world's computing for more than 50 years and gave many of the early computer companies their starts.