Mobile computing is becoming increasingly ubiquitous. From Chromebooks to smartphones and tablets - and even smartwatches and smart glasses - it is possible to carry huge amounts processing power with us each day.
But the success of these devices is due at least in part to the pioneering work of many companies in decades past.
Important milestones in portable computing include devices such as single chip calculators, "laptops" that weighed nearly two stone, digital organisers and even a few older Apple inventions. Here's a look at 21 of the most notable mobile computers.
1. 1971: Busicom LE-120A 'Handy-LE' calculator
Milestone: First pocket-size calculator
Legacy: It might seem strange to kick off a list of portable computing milestones with a calculator, but this little machine from Busicom was one of the first handheld devices that could carry out a computing function. So-called handheld calculators existed before this product, but the Handy-LE was truly the first calculator you could easily hold in your hand or fit in your pocket. The Handy-LE's small size was due to the single-chip calculator circuit, the Mostek MK610, that carried out the device's computing functions.
2. 1978: Parker Bros. Merlin computer toy
Milestone: Early mass-market computer toy
Legacy: It may have been a toy, but the Parker Bros Merlin was one of the earliest portable computers that many children growing up in the late '70s and early '80s encountered. The device had a simple microprocessor and could play six different games: Tic-Tac-Toe, Echo, Blackjack, Magic Square, Mindbender and Music Machine. The last game provided the device with limited programmability, allowing you to input up to 48 tones and rests and have the computer play back your composition.
3. 1981: Osborne 1 portable computer
Milestone: The first computer made for picking up and carrying with you (it doubled as a weight training device)
Legacy: Although the Osborne 1 wasn't light at 23.5 pounds, it was the very first computer designed for users to pack up and tote. The computer offered a 5-inch diagonal screen, two full size floppy drives, a keyboard that snapped onto the system, and a handle in the back for easy carrying.
4. 1982: Grid Compass 1100 clamshell laptop
Milestone: Considered the first clamshell laptop
Legacy: The Grid Compass changed portable computing forever when the manufacturer came up with the brilliant idea of having the display fold over the keyboard. That basic concept remains the standard in laptop design.
5. 1983: TRS-80 Model 100 portable PC
Milestone: Early portable computer popular with telecommuters
Legacy: Sold by Radio Shack and weighing 4 pounds, Tandy's TRS-80 Model 100 was one of the first computers light enough for people to carry around on a daily basis. The Model 100 proved to be particularly popular with journalists. Microsoft co-founder Bill Gates said in an interview with the Smithsonian Institution in 1993 that one of the last machines he wrote a large amount of the code for was the TRS-80 Model 100.
6. 1984: Psion Organiser handheld computer
Milestone: The first handheld computer
Legacy: This organiser, the first from Psion, was the earliest device that could truly be considered a handheld personal computer. The Psion Organiser included a calculator, a calendar and a BASIC-like programming language. Psion's handheld devices were predecessors of the open source Symbian mobile phone operating system maintained by Nokia.
7. 1991: Psion Series 3 minicomputer
Milestone: First palmtop minicomputer
Legacy: An early ancestor of the netbook, the Psion 3 was a miniature clamshell personal organiser that featured a word processor, a spreadsheet, a contacts database, a sketch program, a calculator and a clock.
8. 1996: Palm Pilot 1000 digital planner
Milestone: First popular digital day planner
Legacy: Psion devices and Apple's Newton may have come before it, but the Palm Pilot 1000 was the first truly popular personal digital assistant. The PDA let you keep a to do list, a calendar, a contacts database and short memos all in a small, stylus input-based handheld device. Later Palm devices were among the first to popularise "beaming" information between devices using an infrared port. Palm's Graffiti handwriting recognition technology also did a far better job at accepting stylus input than Newton and earlier handwriting systems did.
9. 1996: Panasonic Toughbook CF-25 laptop
Milestone: The battle-ready laptop
Legacy: The Toughbook CF-25 laptop was housed in a sturdy aluminium alloy case and designed to survive a 2 foot drop. It could also perform under tough environmental conditions such as heat, dust and humidity. Battlefield commanders, police officers and emergency responders were among the first to put the CF-25 to the test. The original tough guy computer may be obsolete today, but the Toughbook line is still going strong.
10. 1999: Apple iBook G3 Wi-Fi enabled laptop
Milestone: First consumer device to carry a Wi-Fi card
Legacy: Apple's iBook G3 was hailed not only for its candy coloured design but also for being one of the first consumer laptops to sport a Wi-Fi card. Many other laptops soon came on the market with Wi-Fi capability, kicking off the era of wireless Internet connectivity.
Milestone: Early pen-based convertible laptop/tablet hybrid
Legacy: The TravelMate was one of the first devices to come loaded with Windows XP Tablet PC Edition. Acer's TravelMate 100 was also notable for being one of the first laptops that let users rotate the screen 180 degrees and lay it flat on the keyboard with the display facing out. Convertible laptops became a standard offering for anyone looking for a tablet PC. Despite Microsoft's enthusiasm for slates, however, the tablet concept wouldn't take off for another eight years, remaining a niche idea until Apple introduced the one panel iPad in 2010.
12. 2002: RIM BlackBerry 5810 handheld email machine/phone
Milestone: Early modern smartphone
Legacy: The BlackBerry 5810 was neither the first device to come out of Canada's Research In Motion nor the first PDA to include phone capabilities. But it was the first of RIM's handheld email machines to include a phone function, and it would lead to RIM's dominance of the enterprise smartphone market. The device popularised several technologies that users value in smartphones today, such as push email and end-to-end data encryption.
13. 2006: Samsung Q1 Ultra-Mobile PC
Milestone: Early ultraportable PC
Legacy: The Samsung Q1 featured a 7-inch display, a 900MHz processor and 500MB of RAM, and it ran a modified version of Windows XP. The UMPC form factor's popularity was short lived due to the device's high price (the Q1 cost $1100) and the introduction of more successful touch-based smartphones and tablets in the following years. Nevertheless, the ability to pack a fair amount of computing power into such a small device was notable for the time. UMPCs are still being manufactured by companies such as OQO and General Dynamics.
14. 2007: Eee PC 4G netbook
Milestone: First netbook, early laptop with solid-state drive
Legacy: Netbooks may soon become irrelevant due to the dominance of tablet devices such as the iPad, but these mini-laptops were an important development in portable computing. They offered an inexpensive way to get your hands on a relatively usable laptop. Around the same time as the Eee PC hit the market, the One Laptop Per Child campaign began offering cheap, durable laptops to children in developing nations. In the developed world, netbooks were soon followed by ultraportable laptops such as the MacBook Air and Dell Adamo. The Eee PC is also notable for using solid-state memory instead of a spinning hard drive. These days, many portable devices rely on SSDs instead of hard drives, including smartphones and Apple's new MacBook Air.
15. 2007: Apple iPhone smartphone
Milestone: Intuitive touch-based interface that turned the smartphone into a minicomputer
Legacy: Apple's first iPhone, with its intuitive interface and powerful computing ability, changed the way we think about smartphones. The handset's seamless integration with iTunes also made it an ideal device for listening to music or watching videos on the go. Before the iPhone, smartphones were typically difficult to navigate, had small displays combined with larger physical keyboards and were often frustrating to use.
16. 2008: Apple iTunes App Store
Milestone: Sparked the third party application craze
Legacy: The App Store may not be a device, but it's hard to imagine what modern smartphones and tablets would be like without the introduction of Apple's third party app scheme. Users have loved the variety of apps available for the iPhone (and later the iPad), including games, utilities, productivity applications, ebooks and communication tools. Numerous competitors, including Google, Microsoft, Nokia, Palm and RIM, have tried to replicate Apple's App Store success.
17. 2010-2011: Apple iPad 1 and 2
Milestone: First mass selling tablet PC
Legacy: No one was really sure what to make of the iPad when it debuted. The device was too weak to be a laptop replacement, but too large to substitute for a smartphone. Currently the tablet serves as a complimentary piece of technology for home users who want to read, manage email or watch a video without lugging around a laptop. Professionals, meanwhile, are using the iPad to track medical charts or to give lectures and presentations.
18. 2011: Motorola Atrix 4G smartphone
Milestone: Webtop/smartphone hybrid
Legacy: The Motorola Atrix 4G could very well represent the future of mobile and desktop computing. The device works as a regular smartphone, but if you connect it to an external monitor, keyboard and mouse, it can run a full version of Mozilla's Firefox browser as well as any installed mobile apps. Business users can also access a virtualised Windows desktop on the Atrix 4G through Citrix XenApp.
19. 2011: Google Chromebook
Milestone: Low cost browser-based laptop
Legacy: Taking up where the failed netbook experiment left off, Google’s cheap Chromebook promised to meet simple computing demands through its browser-based operating system. And it has largely delivered. With a number of hardware vendors such as HP, Dell and Samsung putting their weight behind the low-cost computing platform, it is now possible to get an entry-level version of pricier Ultrabooks for under a couple of hundred quid.
20. 2013: Google Glass
Milestone: Early example of ‘smart-glasses’ technology
Legacy: Google’s audacious smart-glasses plans may have been scaled back following the closure of its prototype Explorer project, but its Google Glass specs certainly captured people’s attention upon launching, even if it was just pointing and laughing at ‘Glass-holes’ wearing the specs. Nevertheless it is likely to return.
Google says it now plans to return with a new version of the device, and could focus more on applications of the technology with businesses rather than consumers.
21. 2015: Apple Watch?
Milestone: First mass market smartwatch?
Legacy: Following many months of speculation the Cupertino-based firm finally unveiled its Apple Watch device in September last year. Up to now there has been plenty of hype around wearable computing, but little to back it up. The same was once true of the MP3 market before Apple launched its iPod, so many are predicting a repeat when it launches in April.