Android Operating System : Some Facts

What is Android?

Android is a Linux-based operating system for mobile devices such as smart phones and tablet computers. It is developed by the Open Handset Alliance led by Google.

Some History about Android

Android, Inc. was founded in Palo Alto, California, United States in October, 2003 by Andy Rubin (co-founder ofDanger),Rich Miner (co-founder of Wildfire Communications, Inc.), Nick Sears (once VP at T-Mobile) and Chris White.

Acquisition By Google

Google acquired Android Inc. on August 17, 2005, making Android Inc. a wholly owned subsidiary of Google Inc. Key employees of Android Inc., including Andy Rubin, Rich Miner and Chris White, stayed at the company after the acquisition.

Android Versions and its Pet Names

2.3 Gingerbread

3.0 Honeycomb

4.0 Ice Cream Sandwich

Courtesy : Wiki pedia 

.DMG Vs .EXE

What the exetensions .dmg and .exe mean ?

.exe files are windows executables; they need windows to run.

.dmg are Apple Disk Image files, which can contain mac executables and/or other data.

ACID Property : Database Transactions

ACID is a set of properties that guarantee database transactions are processed reliably.

Atomicity

Atomicity requires that database modifications must follow an "all or nothing" rule. Each transaction is said to be atomic. If one part of the transaction fails, the entire transaction fails and the database state is left unchanged. An atomic system must guarantee atomicity in each and every situation, including power failures, errors, and crashes. This guarantees that a transaction cannot be left in an incomplete state.

Consistency

The consistency property ensures that any transaction will bring the database from one valid state to another. Any data written to the database must be valid according to all defined rules, including but not limited to constraints, cascades, triggers, and any combination thereof.

Isolation

Isolation refers to the requirement that no transaction should be able to interfere with another transaction. No transactions that affect the same rows can run concurrently, since their sequence, and hence the outcome, would be unpredictable. This property of ACID is often partly relaxed due to the huge speed decrease this type of concurrency management entails.

Durability

Durability means that once a transaction has been committed, it will remain so, even in the event of power loss, crashes, or errors. In a relational database, for instance, once a group of SQL statements execute, the results need to be stored permanently. If the database crashes immediately thereafter, it should be possible to restore the database to the state after the last transaction committed.

Objective Question Bank for HSST Computer Science By Post

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Operating System By Silberschatz and Galvin

Addison Wesley - Silberschatz, Galvin, Gagne - Operating System Concepts, 7th Ed.pdf

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