Devices have been used to aid computation for thousands of years, mostly using one­to­one correspondence with fingers . The earliest counting device was probably a form of tally stick
.
Later record keeping aids throughout the
Fertile Crescent included calculi (clay spheres, cones, etc.) which represented counts of items, probably livestock or grains, sealed in hollow
[4]
[5] unbaked clay containers. The use of counting rods is one example.

Suanpan (the number represented on this abacus is 6,302,715,408)

The abacus was initially used for arithmetic tasks. What we now call the
Roman abacus was used in
Babylonia
as early as 2400 BC. Since then, many other forms of reckoning boards or tables have been invented. In a medieval European counting house
, a checkered cloth would be placed on a table, and markers moved around on it according to certain rules, as an aid to calculating sums of money.

The ancient Greek­designed
Antikythera mechanism
, dating between 150 to 100 BC, is the world's oldest analog computer. The
Antikythera mechanism is believed to be the earliest mechanical analog "computer", according to
Derek J. de Solla Price
.[6]
It was designed to calculate astronomical positions. It was discovered in 1901 in the
Antikythera wreck off the Greek island of
Antikythera
, between
Kythera
and
Crete
, and has been dated to circa 100 BC. Devices of a level of complexity comparable to that of the Antikythera mechanism would not reappear until a thousand years later. Many mechanical aids to calculation and measurement were constructed for astronomical and navigation use. The planisphere was a star chart invented by Abū Rayhān al­Bīrūnī in the
[7]
early 11th century. The astrolabe was invented in the
Hellenistic world in either the 1st or

2nd centuries BC and is often attributed to
Hipparchus
. A combination of the planisphere and dioptra , the astrolabe was effectively an analog computer capable of working out several different kinds of problems in spherical astronomy
. An astrolabe incorporating a mechanical
[8]
[9] calendar computer and gear ­wheels was invented by Abi Bakr of
Isfahan
,
Persia
in
[10]
1235.
Abū Rayhān al­Bīrūnī invented the first mechanical geared lunisolar calendar
[11]
[12] astrolabe, an early fixed­ wired knowledge processing machine with a gear train and
[13]
gear­wheels, circa 1000 AD.

The sector , a calculating instrument used for solving problems in proportion, trigonometry, multiplication and division, and for various functions, such as squares and cube roots, was developed in the late 16th century and found application in gunnery, surveying and navigation. The planimeter was a manual instrument to calculate the area of a closed figure by tracing over it with a mechanical linkage.

A slide rule

The slide rule was invented around 1620–1630, shortly after the publication of the concept of the logarithm . It is a hand­operated analog computer for doing multiplication and division. As slide rule development progressed, added scales provided reciprocals, squares and square roots, cubes and cube roots, as well as transcendental functions such as logarithms and exponentials, circular and hyperbolic trigonometry and other functions . Aviation is one of the few fields where slide rules are still in widespread use, particularly for solving time–distance problems in light aircraft. To save space and for ease of reading, these are typically circular devices rather than the classic linear slide rule shape. A popular example is the
E6B
.
In the 1770s
Pierre Jaquet­Droz
, a Swiss watchmaker , built a mechanical doll ( automata ) that could write holding a quill pen. By switching the number and order of its internal wheels different letters, and hence different messages, could be produced. In