Internetworking Technology

Archive for the ‘Software Management’ Category

In common there are various kinds of software existing in the market. The existing one can choose the software that relies on the application. In few occasions the customer or the business makes unusual software they require, but the profitable products are improved to execute the job that every user wants to do. At olden days system and application software were built-in to the acquiring price of the system. The client should pay spitted amounts for purchasing the software of the system and application software. Some of the software conditions followed in the software ground is conversed as given below. It comes as freeware, shareware, public domain software, cripple ware and firmware. Here on, we can discus about the freeware in a broad manner. Freeware is software which is circulated in a method that permits persons and non-profit institution to make use of software.

The possession of the software product is the original author of the product, even if the software is being supplied free. The end user of this software does not have any rights to do any software modification. Mostly all software launches with its license agreement that forbids the software being borrowed sold or otherwise bothered for a gain manner. Launching software for the purposes of testing is known as Shareware. The software’ author persuades and permits the client to allocate software with each another.

Even though shareware software is considered as pirated if it is not listed and paid prior to the expiration of the testing period. Contrasting shareware or freeware, there is none rights limitations for the common domain software. So such type of software will not be limited to any license agreement and the end user of the software will be usually liberated to use the software as they are with no restraint. The software user can change the software with no authorization of the proprietor of the respective software. This kind of software also shared without any restriction.

Dear all! To ensure the data transmitted in a network has no errors, an error detection and correction technique has to be employed. The errors caused by the noise during transmission can be detected by an error detection system and rectified and original signal is reconstructed by an error correction system.

There are several methods to construct an error detection system. Repetition code technique repeats the bits to be transmitted again and again to ensure an error free communication. Parity bits technique introduces an additional bit with the original data to ensure the number of bits. But this can able to detect only the odd number of bits that are incorrect.

Checksum technique produces an arithmetic sum of the message code words of finite word length. Cyclic Redundancy Check (CRC) technique uses a long division operation in which the remainder gives the result while the quotient is discarded. For error correction, the way to go is retransmission. But the type of request varies in different techniques.

In automatic repeat request an acknowledgement message is from the receiver is sent to transmitter after the receiver has correctly received the data. Otherwise the transmitter will resend. Forward error correction technique employs the addition of redundant codes with the original data and can be recovered at the receiver. Here no retransmission is required and hence this is well suited for simplex communication.

Basically, there are three levels of abstraction to be used to view the data base. If any changes made to any of the three levels it may affect other level’s schema. Database is not a stagnant system. Information is continuously added, customized or deleted to and from the database. Though, this should not direct to redesigning and re-implementation of the database. This particular moment, the concept of data inseparably proves beneficial. The aptitude to modify a schema definition in one level without touching a schema definition in the successive higher level is called data independence. There are two levels of data independent.

Logical Data Independence:

The separation of the external view from the conceptual view, which facilitates the users to change the intangible view without affecting the external view or application program, is called logical data independence. Simply it means the immunity of the external model to changes in the conceptual model.

Physical Data Independence:

The separation of the conceptual view from the internal view permits us to provide a logical explanation of the database does not require specifying physical structures.

Architecture:

Database management system is a group of programs that enables users to generate and continue a database. A foremost purpose of a DBMS is to make available users with an intangible view of the database. This means that the system does not offer all the details of data, slightly it hides the details of how the data is stored and maintained. Conversely, in order for the system to be serviceable, data must be retrieved proficiently. This apprehension leads to the design of complex data structures for the representation of data in the database. Since many database system end users are not computer trained, the complexities are hidden from them through several levels of abstraction in order to simplify their interaction with the system. The two important terms that are connected with the architecture are
view and the schema.

View:

Generally, table enclosed with many columns and rows. In some cases, every data interests the user, and sometimes it does not interest the users. In some cases, when only some columns or some rows of a table interest the user.

Schema:

It refers to the complete structure of the database tables that store information such as user profile data, Meta data or structure information.

Reduction in Data Redundancy:

Data redundancy means duplication of data. In non-database systems, all application has its individual separate files. This can frequently lead to redundancy in stored data, which fallout in wastage of space. In file-based systems of a magazine publishing house, the customer department maintains a separate customer details file. A similar file is also kept with the postage handling department. Therefore the same data is duplicated in two different places. The additional problem with this system is that the data may not be updated constantly. If a customer requests a change in their posting addresses to the customer department and the changed address is reflected in customer’s record. On the other hand, it is not assured that the same change is also done in the postage handling department’s file. Once the database system forgets or delays to update this file, it will automatically lead to postage of the subscribed magazine to the old address. A database management system does not retain separate copies of the same data. Every data is kept at single place and different applications pass on to the data from this centrally controlled system. Finally, when the customers require the change in address, it is done at one place where the concerned department’s application uses the data to practice.

Reduction in Inconsistency:

This is a significance of the previous point. Suppose that the customer’s address is represented by two dissimilar entries in the stored database and the database system is not conscious of this duplication then there will be some occasions on which the entries will not agree, when only one of the two entries has been updated.

Sharing of Data:

It allows the presented applications to use the data in the database. It helps in mounting new applications, which will use the similar stored data. Appropriately, shared data, it is possible to satisfy the data requirement of new applications without having twisted any supplementary stored data or with marginal modification. For example in the nationalized banks, the account holder’s name and address can be shared by all the applications. Finally, any changes in the current account policies can be implemented with practically no changes in the table’s structure.

Needs of DBMS:

In olden times, information systems working with stand alone systems for different applications each with their own set of files. This type of information systems implied that data, like addresses, chance of duplication in numerous separate systems, such as an employee’s address. It may be held once in both the payroll system and the personnel system. It results in waste of space and discrepancy. There are some possibilities for the address to be updated in one system but not in the other. The problems mentioned above lead to the development of the database approach. While coming to database approach, an organization attempts to build an incorporated database to maintain all the data requirements of organization. Database management systems are good quality at organizing and managing huge collections of determined data. A DBMS is otherwise called as a suitcase where all the stuff is put so that in one place and easy to reach. It protects data from unlawful access and accidental corruption or loss due to hardware and software failures. This allows concurrent access, denoting that a particular data set can be accessed by one of more users simultaneously. Concurrent access may commence superfluous problems. Dams provide mechanism to prevent concurrent access problems.

Components of a DBMS:

DBMS is a bulky software package that carries out diver’s tasks together with the provisions of facilities to enable the user to way in and transform information in the database. On one hand it is a transitional link between the physical database, operating system and the computer, and on the other hand, the users. Fundamentally, in order to store the data and provide a standardized method for retrieving or changing the data, and finally, the users turn the data into information. The requests for specific information with the help of user interface, that is, application programs. Generally, this request is processed in DBMS’s data manager and following the data manager who requests for the specific records to the file manager. Again, the file manager requests the specific block to the disk manager. Finally, he disk manager retrieves the block and assigned it to file manager, which sends the required record to data manager.

The Processing system developed hugely from its prehistoric years to the recent digital years. There are six types of operating system available from batch processing systems to the latest embedded systems.

Batch Processing Operating System:

Batch operating system is one of the first to progress. This operating system permitted only a program to move at a moment. This kind of operating systems can still be identified in few main outlook computers working group of works. The operating system is the reason for allocating the works according to aging and the materials required. Batch processing operating systems usually mix through large counts of recurring assignments on large systems. So, this operating system will be the best matched for any concern to automate their billing and other payrolls. A catalog of staff will be entered in their monthly payout will be computed and corresponding pay slips would be documented by printing. It is helpful for this reason as these events are repetitive for all employees every month.

Time Sharing or Multi-User Operating System:

Time sharing system is normally followed in computer network that allows different users to allow the same information and software programs on the same system. The multi user operating system designs a user file account, which defines the correct data.

Embedded Operating System:

Embedded Operating System refers to the working system which is self-sufficient in the machine and occupant in ROM. As these systems are generally not used for general purpose, these systems are simpler or less source serious as compared to common purpose OS. Computers that use these operating systems are household machines, car management, energy management and traffic control systems.

Multi-tasking Operating System:

We can execute more than a process in the multi tasking operating system. The workstation is buttoned quickly between the processes. Therefore, a user can work more than a single process at a moment.