chemistry

Lock screen

Lock screen is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lock screen rather than just read about it. In short: A lock screen is a computer user interface element used by various operating systems. They regulate immediate access to a device by requiring the user to perform a certain action in order to receive access, such as entering a password, using a certain button combination, or performing a certain gesture using a device's touchscreen.

Key takeaways

Lock screen belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lock screen to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lock screen from memory before moving on to harder problems.

Reference excerpt

A lock screen is a computer user interface element used by various operating systems. They regulate immediate access to a device by requiring the user to perform a certain action in order to receive access, such as entering a password, using a certain button combination, or performing a certain gesture using a device's touchscreen. There are various authentication methods to get past the lock screen, with the most popular and common ones being personal identification numbers (PINs), the Android pattern lock, and biometrics (e.g. Touch ID and facial recognition). Depending on the operating system and device type, a lock screen can range from a simple login screen, to an overview screen with the current date and time, weather, recent notifications, playback controls for media being played in the background (typically music), shortcuts to applications (such as the camera), and optionally, the contact information of the device's owner (which can be used if the device is lost or stolen, or during a medical emergency).

Lock screens by platform

Mobile operating systems

Mobile operating systems that run on smartphones and tablets typically use a gesture based lock-screen. Phones manufactured by Neonode were unlocked by swiping right on the touchscreen. Apple's iOS, used by the iPhone and iPad lines, utilized a similar unlock mechanism until iOS 10, with an on-screen slider slid to the right. Beginning on iOS 5, sliding in the other direction sends the user directly to the camera app. On iOS 7, the slider widget was removed as part of a larger overhaul of the iOS interface, and users could now swipe from any point on the screen. The lock screen also displays a clock, notifications, and provides audio playback controls. iOS 10 made major changes to the lock screen, replacing the sliding gesture with pressing the Home button. Swiping is still used to access the camera, as well as an additional page to the left with widgets. As the iPhone X and iPad Pro do not have physical home buttons, the user must swipe upwards from the bottom of the screen instead. At first, Android did not use a gesture-based lock screen, electing to require the user to press the phone's Menu button. On Android 2.0, a new gesture-based lock screen was introduced, displaying two icons: one for unlocking the phone, and one for setting the volume mode, activated by dragging the relevant icon to the center of the screen on a curve (similarly to a rotary dial). On Android 2.1, the rotary dial was replaced by two tabs on either end of the screen. Android 3.0 introduced a new design: a ball with a padlock icon is dragged outside a circular area. On 4.0, the option to unlock straight to the camera is provided, while 4.1 adds the ability to unlock into a Google Search screen by dragging up. Android 4.2 makes additional changes to the lock screen, allowing users to add widgets to pages accessible on the lock screen by swiping from the left edge of the screen. The camera is accessed similarly by swiping from the right edge of the screen. Android also allows devices to be locked using either a password, passcode, a pattern on a grid of 9 circles, fingerprint sensing, or facial recognition. Android distributions by other manufacturers typically use different lock screen designs than what stock Android utilizes; some versions of HTC's Sense used a metallic ring dragged from the bottom of the screen to unlock the phone, and also allows users to launch apps by dragging their respective shortcut icon into the ring instead. On Samsung devices, the lock screen involves dragging in any direction from any location on the screen (TouchWiz Nature devices, such as the Galaxy S III and S4, are also accompanied by a visual effect, such as a pond ripple or lens flare); similarly to HTC's lock screen, app shortcuts can be dragged up from the bottom of the screen to unlock directly into them.

PC operating systems

Windows NT has offered the ability for users to "lock" their computers by displaying a login window, which requires the active user's password to regain access to the system. Since Windows XP, the lock function has also been bound to the keyboard shortcut ⊞ Win+L. On Windows 8, the lock screen was re-designed to closer resemble those used by mobile operating systems; users can choose a distinct wallpaper for use on the lock screen, which now also displays a clock, calendar events, and notifications from other apps. The screen can be dragged upwards with a mouse or touchscreen to unlock the device. Windows 10 maintains this design, whilst adding the ability to use the Cortana voice assistant from the lock screen, and support for slide shows, and the "Windows Spotlight" service to retrieve daily wallpapers and optionally receive advertising and suggestions related to the wallpaper. Screen locking functionality is also built into screensaver systems on some Unix-like operating systems, such as XScreenSaver and gnome-screensaver.

Monetization Particularly on Android, custom lock screen software can be designed to replace the default lock screen with one that displays advertising or otherwise sponsored content. Amazon's Android-based Kindle Fire tablets display notifications of "special offers" on its lock screen, unless users purchase a more expensive SKU of the device which disables this feature. In 2016, Amazon began marketing discounted smartphones exclusive to Amazon Prime subscribers, subsidized by "special offers" and pre-loaded Amazon apps. In November 2017, Google Play Store prohibited apps from displaying advertisements on the lock screen unless the app is specifically designed to replace the lock screen, citing issues with adware embedded in unrelated apps. The Indian company Glance produces a lock screen replacement that displays a content feed on the lock screen, which is monetized via advertising.

Patent litigation

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Lock screen

Start with the simplest possible case. Write down what Lock screen claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lock screen before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lock screen ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lock screen

In research: Lock screen appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lock screen in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lock screen is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer security procedures, Graphical user interface elements, User interface techniques, so understanding it makes those chapters shorter.
In everyday life: Look for Lock screen outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lock screen in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lock screen means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lock screen out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lock screen in simple terms?

Why does Lock screen matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lock screen?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lock screen.