1)A virtual private network, also known as a VPN, is a private network that extends across a public network or internet. It enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network.
VPN is designed to provides a secure , encrypted tunnel in which to transmit the data between the remote user and the company network.The information transmitted between the two locations via the encrypted tunnel cannot be read by anyone else.
2)A check digit is a form of redundancy check used for error detection on identification numbers, such as bank account numbers, which are used in an application where they will at least sometimes be input manually. It is analogous to a binary parity bit used to check for errors in computer-generated data. It consists of one or more digits computed by an algorithm from the other digits (or letters) in the sequence input.
With a check digit, one can detect simple errors in the input of a series of characters (usually digits) such as a single mistyped digit or some permutations of two successive digits.
Check digit are used to protect against the transposition or other transcription errors.
3)SDLC is the acronym of Software Development Life Cycle. It is also called as Software development process. ISO/IEC 12207 is an international standard for software life-cycle processes.
SDLC is a process followed for a software project, within a software organization. It consists of a detailed plan describing how to develop, maintain, replace and alter or enhance specific software. The life cycle defines a methodology for improving the quality of software and the overall development process.
There are following six phases in every SDLC model:
Requirement gathering and analysis, Design, Implementation or coding, Testing, Deployment and Maintenance.
Waterfall Model, Iterative Model, Spiral Model, V-Model, Big Bang Model are the most important and popular models of SDLC.
4)In java, methods operate on the internal state of an object and the object-to-object communication is done via methods. Object A calls a method on object B. This is clearly the simplest type of communication between two objects but is also the way which result in the highest coupling. Object A’s class has a dependency upon object B’s class. Wherever you try to take object A’s class, object B’s class(and all of its dependencies ) are coming with it.
5)LGWR(Log writer) writes log entries to the online redo log files in batches. The redo log buffer entries always contain the most up to date status of the database.
6)A lock is a variable associated with a data item that describes the status of the item with respect to possible operations that can be applied to it. Generally, there is one lock for each data item in the database. Locks are used as a means of synchronizing the access by concurrent transactions to the database item.
Locks placed by a command issued to the DBMS from the application program or query user are called explicit commands.
7)A virtual local area network (VLAN) is a logical group of workstations, servers and network devices that appear to be on the same LAN despite their geographical distribution. A VLAN allows a network of computers and users to communicate in a simulated environment as if they exist in a single LAN and are sharing a single broadcast and multicast domain. VLANs are implemented to achieve scalability, security and ease of network management and can quickly adapt to change in network requirements and relocation of workstations and server nodes.
Higher-end switches allow the functionality and implementation of VLANs. The purpose of implementing a VLAN is to improve the performance of a network or apply appropriate security features.
A Vlan equals to a subnet. It won’t matter if you have 2 PCs on different subnets and you assign the same VLAN to both switch ports. They won’t be able to talk to one another. The subnet ranges must match and VLAN IDs much match for them to talk locally.
8)UML stands for Unified Modeling Language which is used in object oriented software engineering. Although typically used in software engineering it is a rich language that can be used to model an application structures, behavior and even business processes. There are 14 UML diagram types to help you model these behavior.
They can be divided into two main categories; structure diagrams and behavioral diagrams.
9)RSA is one of the first practical public-key cryptosystems and is widely used for secure data transmission. In such a cryptosystem, the encryption key is public and differs from the decryption key which is kept secret.
10)The model database is used as the template for all databases created on an instance of a SQL Server. Because tempdb is created every time SQL Server is started, the model database must always exist a SQL Server System. Modifications made to the model database, such as database size, collation, recovery model and other database options are applied to any databases created afterward.