question: Why are most laptops with a 4K display touch-screen?
comment: Being 4k AND touchscreen is in no way related to each other technically. The feature of being 4k resolution is currently a "premium" feature. Most laptops that have this feature also have the "premium" feature of having a touchscreen. Think of buying a car with all the features, if it has a sunroof, it probably also has power windows.
passages: It is now common for laptop manufacturers to include multi-touch trackpads on their laptops, and tablet computers respond to touch input rather than traditional stylus input and it is supported by many recent operating systems.
   In 2008, the Diamondtouch became a commercial product and is also based on capacitance, but able to differentiate between multiple simultaneous users or rather, the chairs in which each user is seated or the floorpad on which the user is standing. 
  
  In 2007, NORTD labs Open Source system offered its CUBIT (multi-touch).
  
  Small-scale touch devices rapidly became commonplace in 2008. The number of touch screen telephones was expected to increase from 200,000 shipped in 2006 to 21 million in 2012.
  
  In May 2015, Apple was granted a patent for a "fusion keyboard", which turns individual physical keys into multi-touch buttons.
   BULLET::::- In 2004, Italian design firm V12 Design designed a prototype dual-touchscreen laptop known as the Canova.
  
  BULLET::::- In 2007, Pennsylvania-based company Estari released its 2-VU laptop, initially for the United States military before a public release.
  
  BULLET::::- In 2008, the OLPC XO-2 was announced to use a dual-touchscreen setup.
   Section::::Technologies realized.
  
  Section::::Technologies realized.:Multi-touch interfaces.
  
  Multi-touch interfaces, similar to Anderton's, have been put out by Microsoft (2007), Obscura Digital (2008), MIT (2009), Intel (2009), and Microsoft again, this time for their Xbox 360 (2010). A company representative, at the 2007 premiere of the then Microsoft Surface (later renamed to Microsoft PixelSense,) promised it "will feel like Minority Report," and when Microsoft released the Kinect motion sensing camera add-on for their Xbox 360 gaming console in 2010, the Kinect's technology allowed several programmers, including students at MIT, to create "Minority Report" inspired user interfaces.
  
  Section::::Technologies realized.:Retina scanners.
   On June 11, 2012, Apple introduced the 2012 MacBook Pro with a resolution of 2880×1800 or 5.2 megapixels – doubling the pixel density in both dimensions. The laptop shipped with a version of MacOS that provided support to scale the user interface twice as big as it has been previously been. This feature is called HighDPI mode in MacOS and it uses a fixed scaling factor of 2 to increase the size of the user interface for high-DPI screens. Apple also introduced support for scaling the UI by rendering the user interface on higher or smaller resolution that the laptop's built-in native resolution and scaling the output to the laptop screen. One obvious downside of this approach is either a decreased performance on rendering the UI on a higher than native resolution or increased blurriness when rendering lower than native resolution. Thus, while the MacOS's user interface can be scaled using this approach, the UI itself is not resolution-independent.
   Section::::Revisions.:HTC Touch HD.
  
  The HTC Touch HD added the Stock tab and the ability to rearrange or hide tabs. Also, from the Touch HD onwards, TouchFLO 3D was designed for WVGA screens rather than VGA screens.
  
  Section::::Revisions.:HTC Touch Diamond2/HTC Touch Pro2/HTC Tilt 2 (AT&T).
   Such developments could literally change the face of current machines and have far-reaching implications on how users interact with them. Hand-held devices would be designed with larger, easier-to-view screens, as no keyboard would be required. Touch-screen devices would no longer need to split the display between content and an on-screen keyboard, thus providing full-screen viewing of the content. Laptop computers could essentially be cut in half in terms of size, as the keyboard half would be eliminated and all internal components would be integrated behind the display, effectively resulting in a simple tablet computer. Desktop computers would consist of a CPU and screen, saving desktop space otherwise occupied by the keyboard and eliminating sliding keyboard rests built under the desk's surface. Television remote controls and keypads on dozens of other devices, from microwave ovens to photocopiers, could also be eliminated.
   Touchscreens of tablet-type devices, such as the iPad, utilize multi-touch technology, with gestures acting as the main form of user interface. Many touchpads, which in laptops replace the traditional mouse, have similar gesture support. For example, a common gesture is to use two fingers in a downwards or upwards motion to scroll the currently active page. The rising popularity of touchscreen interfaces has led to gestures becoming a more standard feature in computing. Windows 7 introduced touchscreen support and touchpad gestures. Its successor, Windows 8 is designed to run both on traditional desktops and mobile devices and hence gestures are now enabled by default where the hardware allows it.
   The original touch cover came with 80 touch sensors and was pressure sensitive. With the release of the Surface 2 a Touch Cover 2 was announced which increased the number of sensors to 1,092 and added backlit keys while being thinner than the original Touch Cover. In addition, the Touch Cover 2 also supported key gestures and was backwards compatible with the first generation Surface devices. Microsoft never made another Touch Cover after the release of the Surface Pro 3.
  
  Section::::Surface Keyboards.:Type Cover.
   Apple's PowerBook 500 series was its first laptop to carry such a device, which Apple refers to as a "trackpad". When introduced in May 1994, it replaced the trackball of previous PowerBook models. In late 2008 Apple's revisions of the MacBook and MacBook Pro incorporated a "Tactile Touchpad" design with button functionality incorporated into the tracking surface. Beginning in the second generation of MacBook Pro, the entire touchpad surface acts as a clickable button.
   Laptops today feature multitouch touchpads that can sense in some cases up to five fingers simultaneously, providing more options for input, such as the ability to bring up the context menu by tapping two fingers, dragging two fingers for scrolling, or gestures for zoom in/out or rotate.
  
  Psion's MC 200/400/600/WORD Series, introduced in 1989, came with a new mouse-replacing input device similar to a touchpad, although more closely resembling a graphics tablet, as the cursor was positioned by clicking on a specific point on the pad, instead of moving it in the direction of a stroke.
  
  Section::::Theory of operation.
   Apple's first laptop product was the 16-bit lead-acid battery powered 7.2 kg Macintosh Portable released in September 1991. The Portable pioneered inclusion of a pointing device (a trackball) in the laptop/portable sphere.
  
  Section::::Apple.:Powerbook.
  
  The Apple PowerBook series, introduced in October 1991, pioneered changes that are now "de facto" standards on laptops, including room for a palm rest. The following year, IBM released its ThinkPad 700C, featuring a similar design (though with a distinctive red TrackPoint pointing device). 
   In its review of the X1 Carbon Touch, "Wired" wrote, "Lenovo also hasn’t forgotten about the things that users actually care about. Audio is impressive and Dolby-certified. The keyboard is backlit and fully usable, and the glass touchpad was rock solid on this go-round with the Carbon." In its final verdict Wired stated that an "Excellent combination of performance, portability, and durability" and "the best keyboard going" make the Touch 'Wired."
  
  Section::::Models.:2014 – 2nd generation.
   BULLET::::- On 9 September 2013, Lenovo announced the ThinkPad X240s, L440, L540, T440, T440s, T440p, T540p and W540 with Mini DisplayPort.
  
  BULLET::::- On 22 October 2013, Microsoft released the Surface Pro 2, equipped with Windows 8.1 Pro and Mini DisplayPort.
  
  BULLET::::- On 20 June 2014, Microsoft released the Surface Pro 3 with Mini DisplayPort.
  
  BULLET::::- On 5 May 2015, Microsoft released the Surface 3 with Mini DisplayPort.
  
  BULLET::::- On 6 October 2015, Microsoft released the Surface Book, equipped with Windows 10 Pro and Mini DisplayPort.
   Section::::HP TouchSmart All-in-One.:Touchsmart 500.:TouchSmart 600.
  
  The TouchSmart 600 was released on October 13, 2009.
  
  Section::::HP TouchSmart All-in-One.:Business version.
  
  Section::::HP TouchSmart All-in-One.:Business version.:HP TouchSmart 9100.
  
  The TouchSmart 9100 is a business oriented all-in-one PC that bears a strong Recording Assistant to its consumer counterpart, the TouchSmart 600.
  
  Section::::Tablet.
  
  Section::::Tablet.:TouchSmart tx2z.
  
  Released in December 2008, the TouchSmart tx2 was touted as the first consumer notebook and tablet PC with on-screen multi-touch control. The TouchSmart tx2 replaced the older HP Pavilion tx series.
  
  Section::::Tablet.:TouchSmart tm2.
   On September 5, 2014, Dell unveiled the first monitor with a 5K resolution, the UltraSharp UP2715K. This monitor featured a 27-inch 51202880 display, giving it a pixel density of around 218 ppi. The monitor only supported DisplayPort version 1.2, which is limited to 51202880 at 30 Hz. To work around this, the UP2715K implemented a system by which the bandwidth of two DisplayPort connections could be combined to achieve 60 Hz, using a picture-by-picture mode to virtually treat the display as two smaller 25602880 monitors side-by-side and driving each half with a separate DisplayPort connection.
  
  Section::::Display interface and graphics card support.
   BULLET::::- On 10 October 2015, Microsoft released the Surface Pro 4, equipped with Windows 10 Pro and Mini DisplayPort.
  
  BULLET::::- On 2 June 2016, Gigabyte announced the Aero 14 with Mini DisplayPort.
  
  BULLET::::- On 11 November 2016, ECS Liva released the Liva Z Mini PC with Mini DisplayPort.
  
  BULLET::::- On 15 December 2016, Microsoft released the Surface Studio with Mini DisplayPort.
  
  BULLET::::- On 15 June 2017, Microsoft released the Surface Laptop, equipped with Windows 10 S, and the fifth-generation Surface Pro, equipped with Windows 10 Pro, both with Mini DisplayPort.
   Microsoft released minimum hardware requirements for tablet and laplet devices to be "certified" for Windows 8 and defined a convertible form factor as a standalone device that combines the PC, display, and rechargeable power source with a mechanically attached keyboard and pointing device in a single chassis. A convertible can be transformed into a tablet where the attached input devices are hidden or removed leaving the display as the only input mechanism. On March 12, 2013, Microsoft amended its certification requirements to only require that screens on tablets have a minimum resolution of 1024×768 (down from the previous 1366×768). The amended requirement is intended to allow "greater design flexibility" for future products.
   Intel banked on the release of Windows 8 as well as new form factors, such as "convertible" laptops with touchscreens and tablets with keyboard docks, and features (accelerometers and gyroscopes for touchscreens, hand-gesture recognition) to build demand for Ultrabooks. With the third generation Ultrabook specification, introduced in June 2013 alongside its new Haswell processor architecture, Intel also added the requirement for all future Ultrabooks to include touchscreens; the requirement is intended to prevent "game-playing" and market confusion from OEMs, who had offered low-end products with touchscreens but not Ultrabooks.
  
  Section::::Specifications.
   A laptop's integrated screen often requires users to lean over for a better view, which can cause neck or spinal injuries. A larger and higher-quality external screen can be connected to almost any laptop to alleviate this and to provide additional screen space for more productive work. Another solution is to use a computer stand.
  
  Section::::Comparison with desktops.:Disadvantages.:Ergonomics and health effects.:Possible effect on fertility.
   In a review for "Gadling Gear" Kraig Becker wrote,"If you're in the market for a new laptop and you're looking to harness the full potential of Windows 8, the Lenovo Twist is a fantastic choice. I found that once I started using a touch screen notebook it was incredibly difficult to go back to a standard model. Touch just seems like a natural way to interact with our devices now and anything less seems archaic in comparison. Aside from sub-par battery life, I found the Twist to be a great laptop for the average traveler's needs, providing the ability to communicate with friends and family, while staying productive on the road. It's lightweight and thin body make it highly portable and the touch screen simply makes it fun to use. When was the last time you could say that about your laptop?"
   On June 10, 2008, HP unveiled their new HP TouchSmart IQ500 series. The series featured a 22-inch widescreen touchscreen display, an Intel Core 2 Duo processor, a 500GB disk, 256MB NVIDIA GeForce 9300 M HS HD graphics, and 802.11n WiFi, along with an Energy Star qualification. The new TouchSmart featured a 2-inch profile in a piano-black finish.
   BULLET::::- Sticky Multi-monitor setup remembers settings and puts Windows virtual machines back into Full Screen mode on the remote monitor
  
  BULLET::::- Sync iCloud, SkyDrive, Dropbox and more without unnecessary duplication of files
  
  BULLET::::- Windows apps can launch the OS X Mountain Lion Dictionary with Dictionary gesture
  
  BULLET::::- Enhanced integration with MacOS for Linux users
  
  BULLET::::- Enhanced New Virtual Machine Wizard makes it easier to set up a new virtual machine, especially on computers without hard drives
   BULLET::::- Display size: 40 in (101.6 cm) diagonal
  
  BULLET::::- Display resolution: 1920×1080 – 16:9 aspect ratio
  
  BULLET::::- Extensions (ports): HDMI input & output, S/PDIF 5.1 digital audio surround sound out, RCA analog component audio out, 3.5 mm TRS (stereo mini-jack) audio out, 4 USB ports
  
  BULLET::::- Networking: Wi-Fi 802.11n, Bluetooth, and Ethernet 10/100/1000
  
  BULLET::::- Operating system: Windows 7 Professional for Embedded Systems (64-bit)
  
  Section::::Applications development.
  
  Microsoft provides the free Microsoft Surface 2.0 Software Development Kit (SDK) for developers to create NUI touch applications for devices with PixelSense and Windows 7 touch PCs.
   BULLET::::- Multi-touch gestures – Similar to iOS, additional gestures performed using a multi-touch input device (e.g. Magic Mouse, Magic Trackpad) allow the user to scroll, swipe to different pages, and enter Mission Control. While this is not the first official multi-touch support for Mac OS X, it has been expanded; other frameworks, such as Lux, have already created multi-touch support.
  
raw_presuppositions: Having a 4K display is technically related to being touch-screen.
raw_corrections: 4K resolution is a premium feature, and so is touch-screen, so laptops with one usually have the other.