Wearable computer in the context of "Energy harvesting"

Android is an operating system based on a modified version of the Linux kernel and other open-source software, designed primarily for touchscreen-based mobile devices such as smartphones and tablet computers. Android has historically been developed by a consortium of developers known as the Open Handset Alliance, but its most widely used version is primarily developed by Google. First released in 2008, Android is the world's most widely used operating system; it is the most used operating system for smartphones, and also most used for tablets; the latest version, released on June 10, 2025, is Android 16.

At its core, the operating system is known as the Android Open Source Project (AOSP) and is free and open-source software (FOSS) primarily licensed under the Apache License. However, most devices run the proprietary Android version developed by Google, which ships with additional proprietary closed-source software pre-installed, most notably Google Mobile Services (GMS), which includes core apps such as Google Chrome, the digital distribution platform Google Play, and the associated Google Play Services development platform. Firebase Cloud Messaging is used for push notifications. While AOSP is free, the "Android" name and logo are trademarks of Google, who restrict the use of Android branding on "uncertified" products. The majority of smartphones based on AOSP run Google's ecosystem—which is known simply as Android—some with vendor-customized user interfaces and software suites, for example One UI. Numerous modified distributions exist, which include competing Amazon Fire OS, community-developed LineageOS; the source code has also been used to develop a variety of Android distributions on a range of other devices, such as Android TV for televisions, Wear OS for wearables, and Meta Horizon OS for VR headsets.

A smartwatch is a portable wearable computer that resembles a wristwatch. Most modern smartwatches are operated via a touchscreen, and rely on mobile apps that run on a connected device (such as a smartphone) in order to provide core functions.

Early smartwatches were capable of performing basic functions like calculating, displaying digital time, translating text, and playing games. More recent models often offer features comparable to smartphones, including apps, a mobile operating system, Bluetooth and Wi-Fi connectivity, and the ability to function as portable media players or FM radios. Some high-end models have cellular capabilities, allowing users to make and receive phone calls.

Wear OS (formerly Android Wear) is a closed-source Android distribution designed for smartwatches and other wearable computers, developed by Google. Wear OS is designed to pair with mobile phones running Android (version 6.0 "Marshmallow" or newer) or iOS (version 10.0 or newer), providing mobile notifications into a smartwatch form factor and integration with the Google Assistant technology.

Wear OS supports Bluetooth, NFC, Wi-Fi, 3G, and LTE connectivity, as well as a range of features and applications provided through Google Play. Watch face styles include round, square and rectangular. Hardware manufacturing partners include Asus, Broadcom, Fossil, HTC, Intel, LG, MediaTek, Imagination Technologies, Motorola, New Balance, Xiaomi, Qualcomm, Samsung, Huawei, Skagen, Polar, TAG Heuer, Suunto, and Mobvoi.

Smartglasses or smart glasses are eye or head-worn wearable computers. Many smartglasses include displays that add information alongside or to what the wearer sees. Alternatively, smartglasses are sometimes defined as glasses that are able to change their optical properties, such as smart sunglasses that are programmed to change tint by electronic means. Alternatively, smartglasses are sometimes defined as glasses that include headphone functionality.

A pair of smartglasses can be considered an augmented reality device if it performs pose tracking.

A portable computer is a computer designed to be easily moved from one place to another, as opposed to those designed to remain stationary at a single location such as desktops and workstations. These computers usually include a display and keyboard that are directly connected to the main case, all sharing a single power plug together, much like later desktop computers called all-in-ones (AIO) that integrate the system's internal components into the same case as the display. In modern usage, a portable computer usually refers to a very light and compact personal computer such as a laptop, subnotebook or handheld PC, while touchscreen-based handheld ("palmtop") devices such as tablets, phablets and smartphones are called mobile devices instead.

The first commercially sold portable computer might be the 20-pound (9.1 kg) MCM/70, released 1974. The next major portables were the 50-pound (23 kg) IBM 5100 (1975), Osborne's 24-pound (11 kg) CP/M-based Osborne 1 (1981) and Compaq's 28-pound (13 kg), advertised as 100% IBM PC compatible Compaq Portable (1983). These luggable computers still required a continuous connection to an external power source; this limitation was later overcome by the laptop computers. Laptops were followed by lighter models such as netbooks, so that in the 2000s mobile devices and by 2007 smartphones made the term "portable" rather meaningless. The 2010s introduced wearable computers such as smartwatches.