Editing Calculator (section)

====Technical improvements====
[[File:Solar-calculator.jpg|thumb|A calculator which runs on solar and battery power]]
Through the 1970s the hand-held electronic calculator underwent rapid development. The red LED and blue/green [[vacuum fluorescent display]]s consumed a lot of power and the calculators either had a short battery life (often measured in hours, so rechargeable [[nickel-cadmium batteries]] were common) or were large so that they could take larger, higher capacity batteries. In the early 1970s [[liquid-crystal display]]s (LCDs) were in their infancy and there was a great deal of concern that they only had a short operating lifetime. Busicom introduced the Busicom ''LE-120A "HANDY"'' calculator, the first pocket-sized calculator and the first with an LED display, and announced the Busicom ''LC'' with LCD. However, there were problems with this display and the calculator never went on sale. The first successful calculators with LCDs were manufactured by [[Rockwell International]] and sold from 1972 by other companies under such names as: Dataking ''LC-800'', Harden ''DT/12'', Ibico ''086'', Lloyds ''40'', Lloyds ''100'', Prismatic ''500'' (a.k.a. ''P500''), Rapid Data ''Rapidman 1208LC''. The LCDs were an early form using the ''Dynamic Scattering Mode DSM'' with the numbers appearing as bright against a dark background. To present a high-contrast display these models illuminated the LCD using a filament lamp and solid plastic light guide, which negated the low power consumption of the display. These models appear to have been sold only for a year or two.

A more successful series of calculators using a reflective DSM-LCD was launched in 1972 by [[Sharp Inc]] with the Sharp ''EL-805'', which was a slim pocket calculator. This, and another few similar models, used Sharp's ''Calculator On Substrate'' (COS) technology. An extension of one glass plate needed for the liquid crystal display was used as a substrate to mount the needed chips based on a new hybrid technology. The COS technology may have been too costly since it was only used in a few models before Sharp reverted to conventional circuit boards.

[[File:Braun 4856 solar card calculator, 2.jpg|thumb|Credit-card-sized, solar-powered calculator by [[Braun (company)|Braun]] (1987)]]
[[File:Citizen SLD-100NR calculator.jpg|thumb|Modern pocket calculator with solar and battery powering]]
In the mid-1970s the first calculators appeared with field-effect, ''twisted nematic'' (TN) LCDs with dark numerals against a grey background, though the early ones often had a yellow filter over them to cut out damaging [[ultraviolet]] rays. The advantage of LCDs is that they are passive light modulators reflecting light, which require much less power than light-emitting displays such as LEDs or VFDs. This led the way to the first credit-card-sized calculators, such as the [[Casio]] ''Mini Card LC-78'' of 1978, which could run for months of normal use on button cells.

There were also improvements to the electronics inside the calculators. All of the logic functions of a calculator had been squeezed into the first "calculator on a chip" [[integrated circuit]]s (ICs) in 1971, but this was leading edge technology of the time and yields were low and costs were high. Many calculators continued to use two or more ICs, especially the scientific and the programmable ones, into the late 1970s.

The power consumption of the integrated circuits was also reduced, especially with the introduction of [[CMOS]] technology. Appearing in the Sharp "EL-801" in 1972, the [[transistor]]s in the logic cells of CMOS ICs only used any appreciable power when they changed state. The LED and [[Vacuum fluorescent display|VFD]] displays often required added driver transistors or ICs, whereas the LCDs were more amenable to being driven directly by the calculator IC itself.

With this low power consumption came the possibility of using [[solar cell]]s as the power source, realised around 1978 by calculators such as the Royal ''Solar 1'', Sharp ''EL-8026'', and Teal ''Photon''.

<gallery widths="200px" heights="200px">
File:CasioFX20-inside.jpg|The interior of a Casio fx-20 scientific calculator from the mid-1970s, using a VFD. The processor integrated circuit (IC) is made by [[NEC]] (marked μPD978C). Discrete electronic components like [[capacitor]]s and [[resistor]]s and the IC are mounted on a [[printed circuit board]] (PCB). This calculator uses a battery pack as a power source.
File:Sharp el-323 ic 1ae.jpg|The processor chip (integrated circuit package) inside a 1980s Sharp pocket calculator, marked SC6762 1•H. An LCD is directly under the chip. This was a PCB-less design. No discrete components are used. The battery compartment at the top can hold two [[button cell]]s. 
File:Casio fx-992VB interior both aa1.JPG|Inside a Casio scientific calculator from the mid-1990s, showing the processor chip (small square; top-middle; left), keypad contacts, right (with matching contacts on the left), the back of the LCD (top; marked 4L102E), battery compartment, and other components. The solar cell assembly is under the chip.
File:Citizen se-733 int 1ac.jpg|The interior of a newer ({{circa|2000}}) pocket calculator. It uses a button battery in combination with a solar cell. The processor is a "Chip on Board" type, covered with dark [[epoxy]].
</gallery>