Odin mode

Odin mode (or Download mode) is for Samsung Galaxy phones what the name means. You are a God and the phone is a slave. In Odin mode, the user is able to flash whatever wants to the internal flash memory inside the phone by connecting phone to the computer via USB cable. As Odin mode is simple program (in the phone), poor user may not even flash main (Android) system, kernel, recovery system, but this is possible to repartition internal flash and reflash Odin mode itself. If something goes wrong and the Odin mode is broken (erased, rewritten, corrupted), the phone no longer boots and is hard-bricked. So Odin mode is dangerous. Because of this dangerous nature of Odin mode, Odin mode is usually used to only reflash main system or recovery (see warnings below) and if possible, recovery mode is used for flashing (as it is less dangerous).

Source: XDA

Recovery Mode

Recovery Mode

In Android devices, Recovery is an Android-based, lightweight runtime environment separate from and parallel to the main Android operating system. Recovery's original purpose was:

§  to apply software updates to the device, e.g. OTA updates, and

§  to erase user data and cache, e.g. for troubleshooting or preparing the device for resale (factory reset) and

§  to run (another) external tool from microSD flash memory

Recovery is stored in a disk partition separate from the main Android partitions (boot/kernel, root/system). It contains its own Linux kernel, separate from the kernel of the main Android system. Because of separate kernel+recovery_apps, the device is able to boot into the recovery mode even main system is broken some way. Until this recovery partition is not broken, the user has nice tool to fix the device. The recovery has nothing to do with the rest of the (Android) system, so is completely independent.

The bootloader determines whether to boot Android or Recovery.

Recovery Mode

Custom recovery apps

The open-source community has extended the original Android Recovery system, to add other features:

§  system backup and restore (NANDroid),

§  the ability to apply Android changes that aren't approved by the manufacturers or carriers,

§  improved user interface, including using the touch screen instead of only the volume and power buttons, and

§  runs adbd, to support ADB connections.

The most popular custom recovery is ClockworkMod Recovery. Others are:

§  4EXT

§  Amon Ra Recovery

§  Team Win Recovery Project (TWRP)

Clock Workmod Recovery

Source : XDA

CWM

ClockworkMod Recovery (CWM) is a replacement recovery option for Android devices, made by Koushik "Koush" Dutta. It is based on the Android 2.1 (Eclair) recovery image. Features includeNandroid backup, adb shell, advanced update.zip options (ignore asserts and signature checks), and file browser for choosing update.zips

The Rom Manager app may be used for installing CWM, overwriting the device's stock recovery. As with the stock recovery, CWM can apply software changes to the device. Unlike the stock recovery, CWM is able to entirely replace the device's primary Android operating system ("flashing a new ROM"), including with aftermarket replacements such as CyanogenMod. Once installed, CWM it is accessed by turning your phone off, then triggering the bootloader prompt by holding down some device-dependent button combination as it is turned on.

CWM is also known as clockwork and CW recovery.

Source : XDA

How to Entering recovery mode on Your phone

This is possible to enter recovery mode by pressing some button combination during boot sequence of the device. The key combination differ from phone to phone, but manufactures usually has similar invocations for similar phones. You have to read a page with instruction for your phone to make sure that you are not doing something weird. When these keys are pressed, the device does not perform normal boot sequence. Instead of this, another partition is picked and kernel+recovery_apps is invoked from this recovery partition, so the rest of the flash is untouched (see custom recovery_apps list above). The combination of pressed keys has nothing to do with the recovery kernel+recovery_apps (ie. what is flashed to the recovery partition, this will be run). Sometimes there is no recovery flashed, so even keys are pressed, no recovery mode is invoked. You may still be able to flash own recovery to the device by Odin mode and use it later.

Example :

Source : XDA

Bootloader

A bootloader is a computer program that loads an operating system (OS) or runtime environment for the computer after completion of the self-tests.

The bootloader configures the device to an initial known state and has a means to select where to start executing the kernel. It can allow you to make this selection, which give you for example the opportunity to start an alternative Linux kernel, or Windows. Because the bootloader is an essential component of the boot process, it is stored in non-volatile memory, such as flash memory.

Bootloaders are written by hardware vendors and are specialized for the hardware they run on.

For Android devices, the bootloader typically starts either Android or Recovery. Android bootloaders often have a basic interactive mode that can be triggered by holding the "volume down" button while the bootloader is executing.

A locked bootloader is one that will only boot an OS that it "approves" of. This may mean that device's boot partition has an approved digital signature, or the carrier ID (CID) hard-coded into the OS matches a value hard-coded into the bootloader itself. See also Wikipedia:Hardware restrictions#Verified/trusted/secure boot and Wikipedia:SIM lock.

For devices with a locked bootloader, booting an unsanctioned OS (e.g. CyanogenMod or Ubuntu) requires the device's owner to first unlock (or even replace[1]) the bootloader. Unlocking the bootloader sometimes voids the device's warranty. Procedures vary typically by manufacturer.

Bootloader unlocking should not be confused with Android rooting.

Source : XDA, Wikipedia

Gorilla Glass III

Gorilla Glass is the registered trademark for a toughened glass, manufactured by U.S. glassmaker Corning, Inc.

It became highly popular as a cover glass for portable electronic devices such as high-end mobile phones.

The manufacturer claims that Gorilla Glass offers high scratch resistance and incredible hardness, which allows the use of thinner glass panels on devices, without the inherent fragility, which traditionally comes with thinner thickness.

The invention for manufacturing this sort of protective glass had supposedly been gathering dust for quite some years in Corning's warehouse, until Steve Jobs, Apple's CEO back then, commissioned Corning to develop a new scratch proof display cover glass for the first iPhone.

The rise of touchscreen phones popularity since then has turned the manufacturing of Gorilla Glass into a lucrative business niche for Corning.

In 2012, Corning introduced a second generation of the material, called "Gorilla Glass 2" and devices using it started shipping in the first half the same year. According to the manufacturer, the advantages of the second generation include even thinner construction, higher transparency to light and allows for even better touch sensitivity.

Gorilla Glass 3 was announced in 2013 and the popular Samsung Galaxy S4 (released in the first half of the year) is announced as the first phone to feature it.

The new generation is marketed as having Native Damage Resistance™. Marketing talk aside, the new glass reportedly provides enhanced scratch resistance, reduced scratch visibility, and better retained strength once a scratch occurs. According to the manufacturer, the Gorilla Glass 3 is stronger, and is 3x more scratch-resistant than Gorilla Glass 2. Plus some 40% less scratches are visible once they occur.

Source : GSMarena

Computer Viruses

Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.

Through the course of using the Internet and your computer, you may have come in to contact with computer viruses. Many computer viruses are stopped before they can start, but there is still an ever growing concern as to what do computer viruses do and the list of common computer virus symptoms. A computer virus might corrupt or delete data on your computer, use your email program to spread itself to other computers, or even erase everything on your hard disk.

Computer viruses are often spread by attachments in email messages or instant messaging messages. That is why it is essential that you never open email attachments unless you know who it's from and you are expecting it.

Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files.

Computer viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.

To help avoid computer viruses, it's essential that you keep your computer current with the latest updates and antivirus tools, stay informed about recent threats, run your computer as a standard user (not as administrator), and that you follow a few basic ruleswhen you surf the Internet, download files, and open attachments.

Once a virus is on your computer, its type or the method it used to get there is not as important as removing it and preventing further infection.