Important Computer Abbreviations

Hi friends, I am Ravi Sankar Reddy Guda. Here I am sharing some short forms (abbreviations) related to Computers. This list will be helpful for you in your upcoming competitive exams, especially for upcoming IBPS IT Specialist Officers Online Exam. Happy Reading :)

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Difference Between Dynamic Loading and Dynamic Linking

Dynamic loading is used to obtain better memory-space utilization. With dynamic loading a routine is not loaded until it is called. All routines are kept on disk in a re-locatable load format. The main program is loaded into memory and is executed. When a routine needs to call another routine, the calling routine first checks whether the other routine has been loaded or not. The re-allocatable linking loader is called to load the desired routine into memory and to update the program's address tables to reflect this change. Then, control is passed to the newly loaded routine. Loading with bad time dynamic link libraries takes a little longer since, the loader has more work to do, but it saves a lot of disk space that would have been wasted with duplicate copies of every module.

The concept of dynamic linking is similar to that of dynamic loading. Rather than loading is being postponed until execution time, linking is postponed. This feature is usually used with system libraries, such as language subroutine libraries. Without this facility, all programs on a system need to have a copy of their language library (or at least the routines referenced by the program) included in the executable image. This requirement wastes both disk space and main memory. With dynamic linking, a stub is included in the image for each library-routine reference. This stub is a small piece of code that indicates how to locate the appropriate memory-resident library routine, or how to load the library if the routine is not already present.

When this stub is executed, it checks whether the needed routine is already in memory. If the routine is not in memory, the program loads it into memory. Either way, the stub replaces itself with the address of the routine, and executes the routine. Thus, the next time that code segment is reached, the library routine is executed directly, incurring on cost for dynamic linking. Under this scheme, all processes that use a language library execute only one copy of the library code. 

Sai Spandana. Kotturi

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Interpreter - Introduction, Advantages and Disadvantages

Friends, in our previous posts we have discussed about compilers and it's Phases in detail. Today we shall discuss about Interpreter. Generally we call the person who translate from one language to another as an Interpreter. According to Computer Science, the Interpreter is a Software Program. It translates an instruction into a machine language and executes it before proceeding to the next instruction. The main difference between the Compiler and Interpreter is, the compiler translates high-level instructions directly into machine language whereas the Interpreter translates high-level instructions into an intermediate form, which it then executes.

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Compilers Basics for IBPS IT Officers Exam

Assume that you visited china to meet China's Prime minister. The meeting was arranged in a big auditorium. But now the problem is, you don't know Chinese and he too don't know your Language (say Hindi). Then what  to Do? Now you have 3 solutions.

1. To learn Chinese
2. To make him learn your Language
3. Or you both should learn some other language (Like English) so that you can communicate in that language...

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The Phases of Compiler

There are several Phases in compilers are there. Those are,

1. Lexical Analyser : Performs Lexical Analysis 
2. Syntax Analyser : Performs Syntax Analysis
3. Semantic Analyser : Performs Semantic Analysis
4. Intermediate Code Generator : Performs Intermediate Code Generation
5. Code Optimizer : Performs Code Optimization
6. Code Generator : Generates Target Code 

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The OSI Model - Study Materials for IBPS IT Officers Exam 2013

Once there was an Organization called International Standards Organization (ISO in short). It standardized the functions of the Communications System with abstraction layer and developed a Model. They named it as Open Systems Interconnection (OSI). ISO - OSI sounds funny, isn't it???

In this model, similar types of communication functions are grouped into Layers. There are 7 layers in this Model. Those are,

1. Physical Layer
2. Data link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer 

Each layer helps it's above layer to establish an error free communication, in other words, each layer depends on its below layer to establish an error free communication. 

How to remember these names????

Here the order is very important. If anybody asks you about these layers, you should start with Physical and end with Application Layer. You should not jumble these names according to your convenience. So you should remember these names with an order. Well, there are several techniques are there to remember these type of names. One of those technique is, making a funny name or sentence with the STARTING letters. Just, write the starting letters of these layers.

                                         P D N T S P A

Now make a funny sentence, here are some examples

• Please Do Not Touch Steve's Pet Alligator  

                       Or

• Please Do Not Throw Sausage Pizza Away 

Now I bet you never going to forget these names and order again :)

Ok, now lets have a look at the Functionalities of these Layers...

• Physical Layer : This is the First or Lowest layer of the OSI model. It takes care about the Physical Connections.
• Data Link Layer : This layer Encodes the data packets and provides error free node to node transmission. It is divided into two sub layers. Those are
• Media Access Control Layer (MAC Sublayer in short)
• It helps the computer to get the access of data transmission 
• Logical Link Control Layer (LLC Sublayer in short)
• It controls the order, flow and errors of the frames (Frame synchronization)
• Network Layer : This layer helps in Switching and Routing (connecting and transmitting), and also creates virtual circuits ( Imaginary paths for transmission)
• Transport Layer : This layer helps in providing Transparent data transmission. Its also checks whether the data completely transmitted or not.
• Session Layer : This layer is responsible for the Transmission Sessions. I mean Starting, Maintaining and Terminating the Communication. 
• Presentation Layer : This layer provides the data Independence ( simply you can remember that this layer is responsible for the data Presentation :) I mean, how you are presenting data (without any leakage)
• Application Layer : This is the topmost layer, this layer directly interacts with the end user. This layer is responsible for checking whether the claimed user is genuine or not. 

          Still having problems with these functions??? Have a look at the following diagram. It will be easier for you to understand :)

Very good. Now you know about the OSI model and It's Layers :) You know that it was developed by ISO.

Hey, you know one secret? ISO dint invent any new model. It just COPIED some old model and modified it.. Thats all.

Once there was a model called TCP/IP model (Transport Control Protocol / Internet Protocol) with this name itself, you can define its functionality :) It has lil complicated structure with only  4 Layers. Those are

1. Network Interface Layer
2. Internet Layer
3. Transport Layer
4. Application Layer

ISO Just elaborated this model and divided some of these layers into EXTRA LAYERS and developed OSI model. have a look at the following Diagram, so that you can understand the difference :)

Thats all for now friends. Happy reading...

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DBMS Study Material for IBPS IT Officers - Data Models

Read the basics HERE

Data Model means, to give a SHAPE to the data. A Data Model Makes it easier to understand the Data. We can define the data model as "The Collection of High-Level data description that hide many low level storage details". 

The Data Models are divided into THREE different groups. They are,

1. Object - Based Logical Models
2. Record - Based Logical Models
3. Physical Data Models

1. Object Based Logical Models :  These are used in describing data at Logical Level and View Level. ( Logical level describes what data are stored in the database and what relationships exists among those Data. This logical level is used by the DBA (Data Base Administrator). He must decide what information is to be kept in the Data Base. The View level describes Only part of the entire database to be viewed by the user of the database hiding the details of the Information Stored. 

The Object based logical models are described in the different following models.

• The E-R (Entity-Relationship ) Model
• The Object-Based Logical Model
• The Semantic Data Model
• The Functional Data Model

E-R Model : The entity is a "Thing" or " Object" in the real world that is distinguishable from other objects. The E-R model is based on the collection of basic objects called Entities and the Relationship among them. Consider the following Diagram.

In the above diagram, RECTANGLES represents ENTITIES, DIAMONDS represents RELATIONSHIP among those ENTITIES. LINES represents links of Entities to Relationships. 

Object - Oriented Model : The Object Oriented model based on a collection of OBJECTS. An object contains values stored in Instance Variables and Bodies of Code that operates on the Object. (These bodies of Code is called Methods).

Objects that contain the same types of values and the same methods are grouped together into classes. (A class is the definition of the object). 

Semantic Data Model : A Semantic data model is a more high level data model that makes it easier for a user to give Starting Description of the data in an organization. (Semantic is nothing but the Meaning). These models contain a wide verity of relations that helps to describe a real application scenario. A DBMS cannot support all these relations directly. So it is build only with few relations known as relational model in DBMS. A widely used semantic data model is the Entity-Relationship (ER) data model which allows us to graphically denote entities and relationship between them.

Functional Data Model : The functional data model makes it easier to define functions and call them where ever necessary to process data. 

2. Record - Based Logical Models : 

In this type of models, the data is kept in the form of RECORDS (documents). Thse models describes data at Logical and View Levels. When compared with Object Based Data Models, the record based logical models specifies the overall logical structure of the database and provides higher-level implementation. 

These are of 3 types. Those are,

• Relational Model
• Network Model
• Hierarchical Model

Relational Model : The relational model represents both Data (entities) and Relationships among that data in the form of Tables. Each table contains multiple columns and each column contains a unique name. Have a look at the following table. 

Network Model : Data in the network model are represented by collection of Records and Relationships among data are connected by LINKS. These links can be viewed as Pointers. Have a look at the following diagram.


Hierarchical Model : This is also same as Hierarchical model, the difference is the records in the database are represented in the form of TREES (in Hierarchical way)


3. Physical Data Models: Physical data models are used to describe data at the lowest level, which explains how the data is actually stored using complex low-level data structures. Actually, the physical data models are rarely used.

There are two types in Physical Data Models.

• Unifying Model
• Frame-Memory Model

Read about NORMAL FORMS Here....

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Data Base Users and Administrator - IBPS IT Officers Special

Read Basics HERE

Depeending on their degree of expertise or the mode of their interactions with the DBMS, The Data Base users (people who uses database) can be classified into several groups. 

They are,

• Naive Users
• Online Users
• Application Users
• Sophisticated Users
• Specialized Users

Naive Users : Naive means Lacking Experience, these are the users who need not be aware of the presence of the Data Base System. Example of these type of users is The user of an ATM machine. Because these users only responds to the instructions displayed on the screen (enter your pin number, click here, enter the required money etc). Obviously operations performed by these users are very limited. 

Online Users : These are the users who may communicate with the Data Base directly via an online terminal or indirectly via a user interface and application program. These users are aware of the presence of the Data Base System and may have acquired a certain amount of expertise within the limited interaction they are permitted with a Data Base.

Application Programmers : Professional / Application programmers are those who are responsible for developing application programs or user interface. The application programs could be written in a general-purpose programming language or the commands available to manipulate a database. 

Sophisticated Users : Simply we can say that these are the EXPERIENCED users. These people interact with the system without writing programs. Instead they from their requests in a database query language. They submit each such query to a query processor, whose function is to break down DML (Data Manipulation Language, the language which is used to MAINTAIN the data. we shall discuss about this later) statements into instructions that the storage manager understands. Analysts who submit queries to explore data in the Data Base fall in this category. 

Specialized Users : These are the sophisticated users who write specialized database applications that do not fit into the traditional data-processing framework. Among these applications are computer - aided design systems, knowledge-based and expert systems, systems that store data with complex data types (Ex, Graphics Data and Audio Data) and environment-modeling systems.

DBA (Data Base Administrator) : The person who controls both Data and the Programs that access that data in the Data Base is called the Data Base Administrator (DBA).

Functions of the DBA are,

• Defining Schemas (arrangement of Data)
• Creating Storage Structure and Access Methods ( I mean how to store data and access that)
• Modifying the storage Data
• Granting Authorization Permissions
• Specifying the CONDITIONS of the data storage
• Periodically Updating the Data Base etc.,

Read about the Data Models HERE

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The Transaction Management - IBPS Specialist Officers Study Materials

Read the basics of DBMS here

Asume that you want to transfer some money (Say Rs. 1500) to your friend's account....

You logged in into your bank's site and types your account number.

Later you typed your friend's name and his account number

Later types the amount and clicks on TRANSFER button.

Later???  Rs. 1500 /- TRANSFERS into your friend's account.

Now lets see this process in DBMS's point of view.

YOu entered some money (Rs 1500). The DBMS checks whether the mentioned money is available in your account or not.Assume that you have some 3000 in your account.

If available then it checks the reciepient's Account (Assume that he has Rs. 200 in his account)

Later the DBMS reduces your amount to Rs 1500 and Adds that 1500 to your friend's account.

And makes his account balance as Rs 1700 ( 200 + 1500).

Then shows you a message, something like "TRANSACTION COMPLETED"

yes, this is an example of Transaction.

A transaction is an execution of a user program and is seen by the DBMS as a series or list of actions. (or simply we can remember it as " A transaction is nothing but a List of Actions". These actions include the reading and writing of database.

ACID Properties (important) :

 These are the properties that a transaction should possess in order to avoid failures during concurrent access to a database. The ACID is an acronym which stands for Atomicity, Consistency, Isolation, Durability. Now lets have a look at these properties in detail. Ofcourse, for beginers these all may look same and confusing, read them two or three times. then you can get the exact meanings and differences among them...

• Atomicity : It ensures that the transaction either is executed completely or not at all. Incomplete transaction consequences are not entertained, check an example
• Assume that Shivani has Rs. 500/- in her account and Palvi has Rs. 200/- in her account. Now Shivani transfers an amount of Rs. 50/- to Palvi. A transaction debits the amount from shivani's account, but befrore it could be credited to palvi, if there is a failure, then transaction would stop. So finally Shivani loses Rs. 5o but palvi cant get the amount. This leaves the data in an inconsistent state. If there is a failure during transaction execution , then measures must be taken to get back the data in a form which was in, before transaction (I mean, the 50 shouldnt be deducted from Shivani's account in our case). This is taken care of by transaction management component.
• Consistency : The data in the database must always be in a consistent state. A transaction occurred on a Consistent data should end with the data with another Consistent stage after completion of that transaction. Take the above case, the total of the amounts of Shivani and Palvi are (500+200) is Rs 700/- So, after the Transaction completed, the total amount should be same. i.e., (450+250 = 700). Ofcourse, in intermediate stage, where the amount is deducted from Shivani's account but not yet credited to Palvi, the total would not be same. It is the responsibility of DBMS.
• Durability : Durability ensures that the data remains in a consistent state even after the FAILURE. (This is ensured by keeping copy of the old data in the Disk, till the transaction is COMPLETED). I mean, if shivani is transfering money to Palvi. The money is deducted frm Shivani's account and power gone (before adding the MONEY to palvi's account). Then our DBMS shouldn't save that transaction. This is called Durability.
• Isolation :  All transaction must run in Isolation from one another. I mean, each and every transaction should be kept unaware of other transactions and execute independently. The intermediate results shouldnt be available to other transactions. 

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Computer Networks (Basics) for IBPS IT Officers Exam 2014

Suppose you want to chat with your friend, or want to share your printer with your friend's system. Then you should connect your computer to his/her computer. In simple words, you are just forming a NETWORK by connecting two or more computers. These connections or arrangements are called Computer Networks.  These computers in the Computer Network may attached with cables, telephone lines, radio waves, satellites or infrared light beams.

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Data Base Management Systems (Introduction)

Friends, in this post we shall discuss the basics of DBMS (Data Base Management Systems) which will be helpful for you for IBPS Specialist Officers Exam (IT Officers). 

Before going into details, lets have a look at the basic terminology of DBMS.

Data :  Data is the raw material from which Useful Information is derived. The word data is the Plural form of Datum (but nowadays, people commonly using data for both singular and plural). 

               Simply we can say that, data is a collection of unorganized  facts, but can be made organized into useful information.

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The Keyboard

The KeyBoard 

There are various types of keys are there in Keyboard. 
Namely,

• Typewriter Keys
• FunctionKeys
• Enter Keys
• Windows Keys
• Number Keys / Numeric keys
• Application Keys
• Cursor Control Key

Have a look at the Below image to get a detailed View

Click on the image to get a Detailed View

☞ Back to the Computers Basics

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Computers Basics

Once upon a time, there was a sooper hero named Khan Kapoor Kumar. He was very inteligent (He thinks so). Hez proud of his name. But unfortunately people dont call him with his name. They call him Politician instead.. As days passed by, our sooper hero came to know that the reason behind the villagers treating him like a Politician is because, he lacks of a small organ called BRAIN. So he made an Ironbox and gave some electricity to it. 

When he turned on the switch, it said YES, he marked it as 1

When he turned off the switch, it said NO, he marked it as 0

He became famous with this YES/NO Device. He added some circuits to it, so that it could perform some calculations. So he called it as Calculator. In-order to make his Ironbox remember calculations, he added some memory to it. And named it as Computer. 

He added some Input Devices (Keyboard, Mouse, Scanner, Touch pad, Light-pen, Joystick) to it so that he can talk to it.

He added some Output Devices (Monitor, Speaker, Printer) to it so that the Ironbox can talk to him. 

He felt happy because he developed a semi brain called Computer. So, he wanted to communicate with it.

He said "Hi"

It said "1011"

He said "How are you?"

It said "0110 1010 0101"

Then he realized that his Computer only can understand 1's and 0's. So he tried to talk in 1's and 0's language. Later he realized that its really hard to do that. So he attached a compiler to his Computer. The compiler converts his words into 1's and 0's and gives to the computer. And later converts the computer's response into our sooper hero's language. 

Our hero felt that he almost Did it. But even our Compiler also cant understand our sooper Hero's language. So he developed some languages (C, C++, Java etc) to talk to the compiler. 

So our sooper hero finally managed to build a Computer and Proved that hez a Brainless Brilliant. 

Hardware & Software
How does Computer Work ?
The Keyboard

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