It is difficult to define any one device as the earliest computer. The very definition of a computer has changed and it is therefore impossible to identify the first computer. Many devices once called "computers" would no longer qualify as such by today's standards.
Originally, the term "computer" referred to a person who performed numerical calculations (a
human computer), often with the aid of a
mechanical calculating device. Examples of early mechanical computing devices included the
abacus, the
slide rule and arguably the
astrolabe and the
Antikythera mechanism (which dates from about 150-100 BC). The end of the
Middle Ages saw a re-invigoration of European mathematics and engineering, and
Wilhelm Schickard's 1623 device was the first of a number of mechanical calculators constructed by European engineers.
However, none of those devices fit the modern definition of a computer because they could not be programmed. In 1801,
Joseph Marie Jacquard made an improvement to the
textile loom that used a series of
punched paper cards as a template to allow his loom to weave intricate patterns automatically. The resulting Jacquard loom was an important step in the development of computers because the use of punched cards to define woven patterns can be viewed as an early, albeit limited, form of programmability.
In 1837,
Charles Babbage was the first to conceptualize and design a fully programmable mechanical computer that he called "The
Analytical Engine".
[2] Due to limited finance, and an inability to resist tinkering with the design, Babbage never actually built his Analytical Engine.
Large-scale automated data processing of punched cards was performed for the
US Census in 1890 by
tabulating machines designed by
Herman Hollerith and manufactured by the
Computing Tabulating Recording Corporation, which later became
IBM. By the end of the 19th century a number of technologies that would later prove useful in the realization of practical computers had begun to appear: the
punched card,
boolean algebra, the
vacuum tube (thermionic valve) and the
teleprinter.
During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated
analog computers, which used a direct mechanical or
electrical model of the problem as a basis for
computation. However, these were not programmable and generally lacked the versatility and accuracy of modern digital computers.
Defining characteristics of five first operative digital computers
Computer
Shown working
BinaryElectronicProgrammableTuring completeZuse Z3May 1941
Yes
No
By punched
film stockYes (
1998)
Atanasoff-Berry ComputerSummer 1941
Yes
Yes
No
No
ColossusDecember 1943 / January 1944
Yes
Yes
Partially, by rewiring
No
Harvard Mark I - IBM ASCC1944
No
No
By punched paper tape
No
ENIAC1944
No
Yes
Partially, by rewiring
Yes
1948
No
Yes
By Function Table
ROMYes
A succession of steadily more powerful and flexible computing devices were constructed in the 1930s and 1940s, gradually adding the key features that are seen in modern computers. The use of digital electronics (largely invented by
Claude Shannon in 1937) and more flexible programmability were vitally important steps, but defining one point along this road as "the first digital electronic computer" is difficult
(Shannon 1940). Notable achievements include:
EDSAC was one of the first computers to implement the stored program (
von Neumann) architecture.
Konrad Zuse's
electromechanical "Z machines". The
Z3 (1941) was the first working machine featuring
binary arithmetic, including floating point arithmetic and a measure of programmability. In 1998 the Z3 was proved to be
Turing complete, therefore being the world's first operational computer.
The
Atanasoff-Berry Computer (1941) which used vacuum tube based
computation, binary numbers, and
regenerative capacitor memory.
The secret British
Colossus computer (1944), which had limited programmability but demonstrated that a device using thousands of tubes could be reasonably reliable and electronically reprogrammable. It was used for
breaking German wartime codes.
The
Harvard Mark I (1944), a large-scale electromechanical computer with limited programmability.
The US Army's
Ballistics Research Laboratory ENIAC (1946), which used
decimal arithmetic and was the first general purpose electronic computer, although it initially had an inflexible architecture which essentially required rewiring to change its programming.
Several developers of ENIAC, recognizing its flaws, came up with a far more flexible and elegant design, which came to be known as the stored program architecture or
von Neumann architecture. This design was first formally described by
John von Neumann in the paper "
First Draft of a Report on the EDVAC", published in 1945. A number of projects to develop computers based on the stored program architecture commenced around this time, the first of these being completed in
Great Britain. The first to be demonstrated working was the
Manchester Small-Scale Experimental Machine (SSEM) or "Baby". However, the
EDSAC, completed a year after SSEM, was perhaps the first practical implementation of the stored program design. Shortly thereafter, the machine originally described by von Neumann's paper—
EDVAC—was completed but didn't see full-time use for an additional two years.
Nearly all modern computers implement some form of the stored program architecture, making it the single trait by which the word "computer" is now defined. By this standard, many earlier devices would no longer be called computers by today's definition, but are usually referred to as such in their historical context. While the technologies used in computers have changed dramatically since the first electronic, general-purpose computers of the 1940s, most still use the
von Neumann architecture. The design made the universal computer a practical reality.
Microprocessors are miniaturized devices that often implement stored program
CPUs.
Vacuum tube-based computers were in use throughout the 1950s, but were largely replaced in the 1960s by
transistor-based devices, which were smaller, faster, cheaper, used less power and were more reliable. These factors allowed computers to be produced on an unprecedented commercial scale. By the 1970s, the adoption of
integrated circuit technology and the subsequent creation of
microprocessors such as the
Intel 4004 caused another leap in size, speed, cost and reliability. By the 1980s, computers had become sufficiently small and cheap to replace simple mechanical controls in domestic appliances such as
washing machines. Around the same time, computers became widely accessible for personal use by individuals in the form of
home computers and the now ubiquitous
personal computer. In conjunction with the widespread growth of the
Internet since the 1990s, personal computers are becoming as common as the
television and the
telephone and almost all modern electronic devices contain a computer of some kind.
