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Sunday, January 24, 2010


1.    What do you understand by client-server concept?
A.    A software component that services requests from another software component is called a server.  The component making the requests is the client.
The idea of client/server programming is to maximize the benefits of the desktop. The client and server can be present on the same computer or on geographically distant computer connected over a network . Some of the benefits of C/s computing are :
Flexibility, scalability and cost savings in terms of resource utilization and centralized control.

2.    What is meant by 3-Tier architecture ?
A.    3 Tier architecture is a method of deploying the client/server technology in real –world situations. The 3 tiers are :

•    GUI front-end        - Takes care of the end-user interaction and validation of input
•    Business logic layer    - It encapsulates the business processing logic for the data
entered by the user or the data to be processed and given as output to the user. It can be implemented as a collection of reusable and upgradable software components .
•    Data-processing layer    - It takes care of the data processing , storage and
retrieval of the stored data.

3.    What are the advantages of 3-Tier architecture over 2-Tier architecture?
A.    In 2-tier architecture we only have the application layer and the data-processing layer.
The application layer is a combination of the GUI front-end and the business logic.
The following are the disadvantages of the 2-tier architecture (which in turn are the advantages of 3-tier over 2-tier ) :
•    The application is not easily upgradable.
•    The size of the application is large.

3-tier arch. Provides :
•    Maximum performance
•    Security
•    Ease of maintenance.
4.    What do normalization and Denormalization mean?
Normalization is the process of simplifying the relationship between data elements in a data structure .

The task of the database designer is to structure the data in a way that eliminates unnecessary duplication and provides a rapid search path to all necessary information. The process of dividing the information into separate tables that meet these goals is called Normalization.

Denormalization is the reverse process of normalization wherein the normalized data is merged to form a larger data structure that might have redundant data.

5.          What are the different degrees of normalization?
A.    A relation is in 1st Normal form if and only if all underlying domains contain atomic values only.

A relation is in 2nd normal form if and only if it is in 1NF and every nonkey attribute is fully dependent on the primary key.

A relation is in 3rd Normal form if and only if it is in 2NF and every nonkey attribute is nontransitively dependent on the primary key.

A relation R in 4th normal form if and only if , whenever there exists a multi-valued dependency in R, say A ->-> B (attribute B is multi-dependant on attribute A), then all attributes of R are also functionally dependent on A .

A relation R is said to be in fifth normal form also called Projection Join Normal form (PJNF) if and only if every join dependency in R is implied by the candidate keys of R.

6.    Do you know ODBC?
A.    ODBC is Open-database Connectivity. It provides access to any database which has a
ODBC database driver .
The database can be a client/server database that conform to ODBC standards
eg. SQL Server , Oracle etc.

An ODBC driver-manager provides an interface from the host language to the specific
Back-end data source driver.  The driver manager is responsible for :
•    Loading the remote database drivers specified in the DSN entry
•    Initializing the interface
•    Providing entry points to driver entry points
•    Validating parameters and managing serialization of ODBC functions

ODBC driver is a DLL that can interface with a specific back-end database engine
Eg. MS-SQL server , Oracle , sybase etc.
An ODBC driver takes advantage of specific back-end features such as cursors or parameterized queries . It can also implement some other features not supported by the back-end. If the driver doesn’t support a specific feature it returns an error stating that it doesn’t support the feature .

7.    What are the factors that influence ODBC response time ?
A.    The main factors that influence the ODBC response time are :
•    Network load
•    The complexity of the SQL queries
•    The speed of the machine on which the server executes
•    The RAM of the machine on which the server executes
•    The number of records that are likely to be returned as result of the query.
•    The physical location of the database and number of connections to database

8.    In how many ways can VB implement ODBC ?
A.    VB can implement ODBC in the following ways :
•    Using Data control and connecting to a database like SQL Server , Oracle
•    Using DAO objects and using the dbUseODBC parameter in the CreateWorkspace methods ie. Using ODBC Direct
•    Using Remote Data Control
•    Using Remote Data Objects
•    Using ODBC API calls

9.    What is OOPS ?
A.    OOPS is Object Oriented Programming.  The main features of OOPS are :
Data hiding & encapsulation
Data Abstraction

    The advantages of OOPS over structured programming are :
•    Data hiding
•    Code reusability
•    Lower costs in building systems
•    Flexibility

10.    How VB 5.0 implements OOPS ?
A.    VB implements OOPS concepts in the following ways :\
•    Data hiding is implemented using the “Public , Private  scoping keywords “
•    Polymorphism is implemented using the “Implements “ , ParamArray , Optional keywords
•    Inheritance is implemented in the sense of interface inheritance and not implementation inheritance (ie. Not like C++ inheritance)

11.    Explain code-reusability in OOPS programming / VB ?
A.    In VB we have the concept of ActiveX code components and ActiveX controls. The code for a
certain functionality need not be re-written if the code components /controls are available to the developer. The references to the code components and controls can be set in VB and the functionality exposed by them can be used in one’s projects.  This decreases development time .

12.    What is the difference between the following lines of code ?
Dim X as Object
Dim X as class_name

In the first statement the compiler uses Late Binding of the object. The object to be used is not known until run-time. Because the late binding does not use the type library during the design time, a reference is not set to the component.

In the second statement the compiler uses Early Binding. The object variable refers to a discreet object type and hold pointers only to that object type. VB will have explicit knowledge of the object through its type library by setting a reference to the component. With this VB will be able to display data about the available methods and properties, as well as the syntax of the each method or property called.   

13.    Explain something about Active X and how do you us it?
A.    An ActiveX component is a unit of executable such as an exe or dll or ocx file that follows ActiveX specification for providing objects . An ActiveX component exposes objects that can be used by other applications .
ActiveX components used are ActiveX code components, ActiveX documents , ActiveX  Controls , ActiveX clients.

14.    What is an OLE Server?
A.    An OLE server is a code component that exposes some of its methods and properties to
other applications. An OLE Server can be an In-Process server (implemented as an OLE DLL) or an out-of-process server (OLE EXE) .

15.    Which is more advantageous – using DLLs or objects ?
A.    See in Answer 14.

16.    Do you know about COM / DCOM  ?
A.    COM is Component Object Model. It is an object-oriented architecture for building applications and the foundation on which ActiveX components are built. ActiveX components allow programmers to combine re-usable pieces of code into applications and services .

It specifies the blue-print of how objects can be created from their component.
How a client accesses features of an object.
Object responsibility to destroy itself when not in use .

Advantages of COM :
•    Binary compatibility and cross-platform development
•    Code-resuability
•    Automatic Versioning (Version Control)

DCOM is Distributed Component Object Model. It is an extension of COM. It is a protocol that enables s/w components to directly communicate over a network in a reliable,secure and efficient manner. Some of the key features of DCOM are :

Location independence
Connection mgmt
Band-width and latency
Load balacing
Ease of deployment.
Protocol and Platform neutrality.

17.    What is the difference between ActiveX and Java Beans ?
A.    ActiveX and Java Beans are comparable the only difference which I perceive is that Java Beans are platform neutral and ActiveX controls are dependant on the Windows platforms.

18.    What is Java’s future ?
A.    Microsoft is working on Windows Foundation Classes which proposes to recode the Windows DLLs using Java . Microsoft proposes to enable Java applications to use the WFC and thus bind the Java language to the Windows platforms. This is being strongly contested by Sun .

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