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A mobile device (or handheld computer) is a computer small enough to hold and operate in the hand. Mobile devices typically have a flat LCD or OLED screen, a touchscreen interface, and digital or physical buttons. They may also have a physical keyboard. Many such devices can connect to the Internet and connect with other devices such as car entertainment systems or headsets via Wi-Fi, Bluetooth, cellular networks or near field communication. Integrated cameras, the ability to place and receive voice and video telephone calls, video games, and Global Positioning System (GPS) capabilities are common. Power is typically provided by a lithium-ion battery. Mobile devices may run mobile operating systems that allow third-party applications to be installed and run.
Early smartphones were joined in the late 2000s by larger tablets. Input and output are usually via a touch-screen interface. Phones/tablets and personal digital assistants may provide much of the functionality of a laptop/desktop computer in addition to exclusive features.  Enterprise digital assistants can provide additional business functionality such as integrated data capture via barcode, RFID and smart card readers.
By 2010, mobile devices often contained sensors such as accelerometers, magnetometers and gyroscopes, allowing the detection of orientation and motion. Mobile devices may provide biometric user authentication, such as face recognition or fingerprint recognition.
Major global manufacturers of mobile devices are Samsung, Huawei, Meizu, Zte, Xiaomi, Sony, Google, HTC, LG, TCL, Motorola Mobility, Nokia, Realme and Micromax Informatics.
Device mobility can be viewed in the context of several qualities: 
Strictly speaking, many so-called mobile devices are not mobile. It is the host that is mobile, i.e., a mobile human host carries a non-mobile smartphone device. An example of a true mobile computing device, where the device itself is mobile, is a robot. Another example is an autonomous vehicle.
There are three basic ways mobile devices can be physically bound to mobile hosts: accompanied, surface-mounted, or embedded into the fabric of a host, e.g., an embedded controller in a host device. Accompanied refers to an object being loosely bound and accompanying a mobile host, e.g., a smartphone can be carried in a bag or pocket but can easily be misplaced.  Hence, mobile hosts with embedded devices such as an autonomous vehicle can appear larger than pocket-sized.
The most common size of a mobile computing device is pocket-sized, but other sizes for mobile devices exist. Mark Weiser, known as the father of ubiquitous computing,  referred to device sizes that are tab-sized, pad and board sized,  where tabs are defined as accompanied or wearable centimetre-sized devices, e.g. smartphones, phablets and pads are defined as hand-held decimeter-sized devices. If one changes the form of the mobile devices in terms of being non-planar, one can also have skin devices and tiny dust-sized devices.  Dust refers to miniaturized devices without direct HCI interfaces, e.g., micro-electro-mechanical systems (MEMS), ranging from nanometres through micrometres to millimeters. See also Smart dust. Skin: fabrics based upon light emitting and conductive polymers and organic computer devices. These can be formed into more flexible non-planar display surfaces and products such as clothes and curtains, see OLED display. Also, see smart device.
Although mobility is often regarded as synonymous with having wireless connectivity, these terms are different. Not all network access by mobile users, applications and devices need to be via wireless networks and vice versa. Wireless access devices can be static and mobile users can move in between wired and wireless hotspots such as in Internet cafés.  Some mobile devices can be used as mobile Internet devices to access the Internet while moving, but they do not need to do this and many phone functions or applications are still operational even while disconnected from the Internet.
What makes the mobile device unique compared to other technologies is the inherent flexibility in the hardware and also software. Flexible applications include video chat, Web browsing, payment systems, near field communication, audio recording etc.  As mobile devices become ubiquitous, there will be a proliferation of services which include the use of the cloud.  Although a common form of mobile device, a smartphone, has a display, another perhaps even more common form of smart computing device, the smart card, e.g., used as a bank card or travel card, does not have a display. This mobile device often has a CPU and memory but needs to connect or be inserted into a reader to display its internal data or state.
There are many kinds of mobile devices, designed for different applications. They include:
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Handheld devices have become more rugged for use in mobile field management. This involves tasks such as digitizing notes, sending and receiving invoices, asset management, recording signatures, managing parts and scanning barcodes.
In 2009, developments in mobile collaboration systems enabled the use of handheld devices that combine video, audio and on-screen drawing capabilities to enable multi-party conferencing in real-time, independent of location.  Handheld computers are available in a variety of form factors, including smartphones on the low end, handheld PDAs, Ultra-Mobile PCs and Tablet PCs (Palm OS, WebOS).  Users can watch television through the Internet by IPTV on some mobile devices. Mobile television receivers have existed since the 1960s, and in the 21st-century mobile phone providers began making television available on cellular phones. 
In the 2010s, mobile devices were observed to frequently include the ability to sync and share a variety of data despite the distance or specifications of the devices. In the medical field, mobile devices are quickly becoming essential tools for accessing clinical information such as drugs, treatment, and even medical calculation.  Due to the popularity of mobile gaming, the gambling industry started offering casino games on mobile devices, which led to the inclusion of these devices in the anti-hazard legislature as devices that could potentially be used for illegal gambling. Other potentially illegal activities might include the use of mobile devices in distributing child pornography and the legal sex industry's use of mobile apps and hardware to promote its activities, as well as the possibility of using mobile devices to perform trans-border services, which are all issues that need to be regulated. In the military, mobile devices have created new opportunities for the armed forces to deliver training and educational materials to soldiers, regardless of where they are stationed. 
A personal digital assistant (PDA), also known as a handheld PC, is a variety mobile device which functions as a personal information manager. PDAs have been mostly displaced by the widespread adoption of highly capable smartphones, in particular those based on iOS and Android, seeing a rapid decline in use after 2007.
Ubiquitous computing is a concept in software engineering, hardware engineering and computer science where computing is made to appear anytime and everywhere. In contrast to desktop computing, ubiquitous computing can occur using any device, in any location, and in any format. A user interacts with the computer, which can exist in many different forms, including laptop computers, tablets, smart phones and terminals in everyday objects such as a refrigerator or a pair of glasses. The underlying technologies to support ubiquitous computing include Internet, advanced middleware, operating system, mobile code, sensors, microprocessors, new I/O and user interfaces, computer networks, mobile protocols, location and positioning, and new materials.
A wearable computer, also known as a body-borne computer, is a computing device worn on the body. The definition of 'wearable computer' may be narrow or broad, extending to smartphones or even ordinary wristwatches.
Palm OS was a mobile operating system initially developed by Palm, Inc., for personal digital assistants (PDAs) in 1996. Palm OS was designed for ease of use with a touchscreen-based graphical user interface. It is provided with a suite of basic applications for personal information management. Later versions of the OS have been extended to support smartphones. The software appeared on the company's line of Palm devices while several other licensees have manufactured devices powered by Palm OS.
A Pocket PC is a class of personal digital assistant (PDA) that runs the Windows Mobile or Windows Embedded Compact operating system that has some of the abilities of modern desktop PCs. The name was introduced by Microsoft in 2000 as a rebranding of the Palm-size PC category. Some of these devices also had integrated phone and data capabilities, which were called Pocket PC Phone Edition or simply "Smartphone".
Palm was a line of personal digital assistants (PDAs) and mobile phones developed by California-based Palm, Inc., originally called Palm Computing, Inc. Palm devices are often remembered as "the first wildly popular handheld computers," responsible for ushering in the smartphone era.
Mobile may refer to:
A smartphone is a portable computer device that combines mobile telephone functions and computing functions into one unit. They are distinguished from older-design feature phones by their stronger hardware capabilities and extensive mobile operating systems, which facilitate wider software, access to the internet, and multimedia functionality, alongside core phone functions such as voice calls and text messaging. Smartphones typically contain a number of metal–oxide–semiconductor (MOS) integrated circuit (IC) chips, include various sensors that can be leveraged by pre-installed and third-party software, and support wireless communication protocols. More recently, smartphone manufacturers have begun to integrate satellite messaging connectivity and satellite emergency services into devices for use in remote regions where there is no reliable cellular network.
Mobile computing is human–computer interaction in which a computer is expected to be transported during normal usage and allow for transmission of data, which can include voice and video transmissions. Mobile computing involves mobile communication, mobile hardware, and mobile software. Communication issues include ad hoc networks and infrastructure networks as well as communication properties, protocols, data formats, and concrete technologies. Hardware includes mobile devices or device components. Mobile software deals with the characteristics and requirements of mobile applications.
A smart device is an electronic device, generally connected to other devices or networks via different wireless protocols that can operate to some extent interactively and autonomously. Several notable types of smart devices are smartphones, smart speakers, smart cars, smart thermostats, smart doorbells, smart locks, smart refrigerators, phablets and tablets, smartwatches, smart bands, smart keychains, smart glasses, and many others. The term can also refer to a device that exhibits some properties of ubiquitous computing, including—although not necessarily—machine learning.
A mobile game, or smartphone game, is a video game that is typically played on a mobile phone. The term also refers to all games that are played on any portable device, including from mobile phone, tablet, PDA to handheld game console, portable media player or graphing calculator, with and without network availability. The earliest known game on a mobile phone was a Tetris variant on the Hagenuk MT-2000 device from 1994.
Windows Mobile was a family of mobile operating systems developed by Microsoft for smartphones and personal digital assistants.
Construction field computing is the use of handheld devices that augment the construction superintendent's ability to manage the operations on a construction site. These information appliances (IA) must be portable devices which can be carried or worn by the user, and have computational and connectivity capacity to perform the tasks of communication management. Data entry and retrieval must be simple so that the user can manipulate the device while simultaneously moving, observing events, studying materials, checking quality, or performing other tasks required. Examples of these devices are the PDA, tablet PC modern tablet devices including iPad and Android Tablets and smartphone.
A mobile phone is a portable telephone that can make and receive calls over a radio frequency link while the user is moving within a telephone service area, as opposed to a fixed-location phone. The radio frequency link establishes a connection to the switching systems of a mobile phone operator, which provides access to the public switched telephone network (PSTN). Modern mobile telephone services use a cellular network architecture and therefore mobile telephones are called cellphones in North America. In addition to telephony, digital mobile phones support a variety of other services, such as text messaging, multimedia messagIng, email, Internet access, short-range wireless communications, satellite access, business applications, video games and digital photography. Mobile phones offering only basic capabilities are known as feature phones; mobile phones which offer greatly advanced computing capabilities are referred to as smartphones.
Mobile interaction is the study of interaction between mobile users and computers. Mobile interaction is an aspect of human–computer interaction that emerged when computers became small enough to enable mobile usage, around the 1990s.
Mobile technology is the technology used for cellular communication. Mobile technology has evolved rapidly over the past few years. Since the start of this millennium, a standard mobile device has gone from being no more than a simple two-way pager to being a mobile phone, GPS navigation device, an embedded web browser and instant messaging client, and a handheld gaming console. Many experts believe that the future of computer technology rests in mobile computing with wireless networking. Mobile computing by way of tablet computers is becoming more popular. Tablets are available on the 3G and 4G networks. Mobile technology has different meanings in different aspects, mainly mobile technology in information technology and mobile technology in basketball technology, mainly based on the wireless technology of wireless devices equipment information technology integration.
Jeotex, Inc., known as Datawind, Inc until 2019. and founded in Montreal, Quebec, Canada, is a developer and manufacturer of low-cost tablet computers and smartphones. Datawind manufactures low cost tablets and sells these primarily in India, Nigeria, the United Kingdom, Canada, and the United States. The company is known for its development of the Aakash tablet computer, which is the “world's cheapest tablet” at US$37.99/unit. The Aakash tablet was developed for India's Ministry for Human Resource Development (MHRD).
Pocket-sized computer describes the post-programmable calculator / pre-smartphone pocket-sized portable-office hardware devices that included the earlier DOS-based palmtops and subsequent Windows-CE handhelds, as well as a few other terms, primarily covering the 1980s through 2007.
Roy Want is a computer scientist born in London, United Kingdom in 1961. He received his PhD from Cambridge University (UK) in 1988 for his work on multimedia Distributed Systems; and is known for his work on indoor positioning, mobile and ubiquitous computing, automatic identification and the Internet of Things (IoT). He lives in Silicon Valley, California, and has authored or co-authored over 150 papers and articles on mobile systems, and holds 100+ patents. In 2011 he joined Google as a Senior Research Scientist, and is in the Android group. Previous roles include Senior Principal Engineer at Intel, and Principal Scientist at Xerox PARC...