COMPUTER TALES

Prime Numbers A Prime Number can be divided evenly only by 1 or itself. And it must be a whole number greater than 1. The first few prime numbers are: 2, 3, 5, 7, 11, 13, and 17 ..., and we have a prime number chart if you need more. Factors "Factors" are the numbers you multiply together to get another number: Prime Factorization "Prime Factorization" is finding which prime numbers multiply together to make the original number. Here are some examples: Example 1: What are the prime factors of 12 ? It is best to start working from the smallest prime number, which is 2, so let's check: 12 ÷ 2 = 6 Yes, it divided evenly by 2. We have taken the first step! But 6 is not a prime number, so we need to go further. Let's try 2 again: 6 ÷ 2 = 3 Yes, that worked also. And 3 is a prime number, so we have the answer: 12 = 2 × 2 × 3 As you can see, every f...

A Prime Number can be divided evenly only by 1 or itself. And it must be a whole number greater than 1. Example: 2, 3, 5, 7, 11, etc. Twin Primes A pair of prime numbers that differ by 2 (successive odd numbers that are both Prime numbers). Examples: (3,5) , (5,7) , (11,13) , ... It is not known whether the set of twin prime numbers ends or not. Co-primes or Relatively prime numbers A pair of numbers not having any common factors other than 1 or -1. (Or alternatively their greatest common factor is 1 or -1) Example: 15 and 28 are co-prime, because the factors of 15 (1,3,5,15), and the factors of 28 (1,2,4,7,14,28) are not in common (except for 1). Mersenne's Primes Prime numbers of the form 2 n -1 where n must itself be prime. 3, 7, 31, 127 etc. are Mersenne primes. Not all such numbers are primes. For example, 2047 (i.e. 2 11 -1) is not a prime number...

*  Digital transmission can be either parallel or serial in mode. *  In parallel transmission, a group of bits is sent simultaneously with each bit on a separate line. *  In serial transmission, there is only one line and the bits are sent sequentially. *  Serial transmission can be either synchronous or asynchronous. *  In asynchronous serial transmission, each byte is framed with a start bit and a stop bit. There may. be a variable-length gap between each byte. *  In synchronous serial transmission, bits are sent in a continuous stream without start and stop bits and without gaps between bytes.  *  Regrouping the bits into meaningful bytes is responsibility of the receiver. *  A DTE is.. source or destination for binary digital data. *  A DCE receives data from a DTE and changes it into a form   appropriate for network transmission. It can also perform the reverse transformation. *  A modem is a DCE that...

Keys:  As there are number of keys can be defined, but some commonly and mainly used keys are explained as below: 1. Primary Key       A key is a single attribute or combination of two or more, attributes of an entity that is used to identify one or more instances of the set. The attribute Roll # uniquely identifies an instance of the entity set STUDENT. It tells about student Amrita having address 101, Kashmir Avenue and phone no. 112746 and have paid fees 1500 on basis of Roll No. 15. The 15 is unique value and it gives unique identification of students So here Roll No is unique attribute and such a unique entity identifies called Primary Key. Primary key cannot be duplicate.       From the definition of candidate key, it should be clear that each relation must have at least one candidate key even if it is the combination of all the attributes in the relation since all tuples in a relation are distinct. Some relations may have mor...

It is necessary to describe the organization, of the data in a formal manner. The logical and physical database descriptions are used by DBMS software. The complete and overall description of data is referred to as schema, The schema and subschema words are brought into DBMS by CODASYL (Conference on data system language1 committee) and also by the CODASYL’s database task group. Schema is also referred to as conceptual model or global view (community view) of data. Suppose a complete description of collected data having all classes and student data4 all employees (teaching & non-teaching) data and other concept of data related to the college is called Schema of the college. We can say that we relate whole college data logically, which is called schema.

There are many different framework have been suggested for the DBMS over the last several year. The generalized architecture of a database system is called ANSI/SPARC (American National Standards Institute/Standards Planning and Requirements Committee) model.       In 1972, a final report about database is submitted by ANSI (American National Standard Institute) and SPARC (Standard Planning And Requirement Committee). According to this approach, three levels of a database system was suggested and they are:       • External view (Individual user view)       • Conceptual View (Global or community user view)       • Internal level (physical or storage view).       For the system to be usable, it must retrieve data efficiently. This concern has led to the design of complex data structures for the representation of data in the database. Since many database systems users are not computer traine...

ADVANTAGES OF DBMS       One of the major advantages of using a database system is that the organization can be handled easily and have centralized management and control over the data by the DBA. Some more and main advantages of database management system are given below:       The main advantages of DBMS are: 1. Controlling Redundancy       In a DBMS there is no redundancy (duplicate data). If any type of duplicate data arises, then DBA can control and arrange data in non-redundant way. It stores the data on the basis of a primary key, which is always unique key and have non-redundant information. For example, Roll no is the primary key to store the student data. In traditional file processing, every user group maintains its own files. Each group independently keeps files on their db e.g., students. Therefore, much of the data is stored twice or more. Redundancy leads to several problems:       ...

  various functions of DBMS        • Data definition:  The DBMS must be able to accept data definitions (external schema , the conceptual schema, the internal schema, and all associated mappings) in source form and convert them to the appropriate object form.       • Data manipulation:  The DBMS must be able to handle requests from the users to retrieve, update, or delete existing data the database, or to add new data to the database. In other words, the DBMS must include a data manipulation language (DML) processor component.        • Data security and integrity:  The DBMS must monitor user requests and reject any attempt to violate the security and integrity rules defined by the DBA.        • Data recovery and concurrency:  The DBMS - or else some other related software component, usually called the transaction manager - must enforce certain recovery and concurrency ...

Importance of database Contents Components are important for understanding and designing the database system. Basic Components of DBMS A database system has four components.        1. Data       2. Hardware       3. Software       4. Users 1. Data       As we have discussed above, data is raw hand information collected by us. Data is made up of data item or data aggregate. A Data item is the smallest unit of named data: It may consist of bits or bytes. A Data item is often referred to as field or data element. A Data aggregate is the collection of data items within the record, which is given a name and referred as a whole. Data can be collected orally or written. A database can be integrated and shared. Data stored in a system is partition into one or two databases. So if by chance data lost or damaged at one place, then it can be accessed from the second place by using the sharing facility of ...

A DBMS is best described as a collection of programs that manage the database structure and that control shared access to the data in the database. Current DBMSes also store the relationships between the database components; they also take care of defining the required access paths to those components       A database management system (DBMS) is the combination of data, hardware, software and users to help an enterprise manage its operational data.       The main function of a DBMS is to provide efficient and reliable methods of data retrieval to many users. Efficient data retrieval is an essential function of database systems. DBMS must be able to deal with several users who try to simultaneously access several items and most frequently, the same data item A DBMS is a set of programs that is used to store and manipulation data that include the following:       • Adding new data, for example adding details of new student...

1. Self-contained nature       DBMS system contains data plus a full description of the data (called “metadata”) “metadata” is data about data - data formats, record structures, locations, how to access, indexes metadata is stored in a catalog and is used by DBMS software to know how to access the data. Contrast this with the file processing approach where application programs need to know the structure and format of records and data. 2. Program-data independence       Data independence is immunity of application programs to changes in storage structures and access techniques. E.g. adding a new field, changing index structure, changing data format, In a DBMS environment these changes are reflected in the catalog. Applications aren’t affected. Traditional file processing programs would all have to change, possibly substantially. 3. Data abstraction       A DBMS provides users with a conceptual representation of data (...

The major characteristics of database approach are:       • Self-describing Nature of a Database System       • Insulation between Programs and Data, and Data Abstraction       • Support of Multiple Views of the Data       • Sharing of Data and Multi user Transaction Processing

      A database is a collection of occurrence of multiple record types containing the relationship between records, data aggregate and data items. A database may be defined as       A database is a collection of interrelated data store together without harmful and unnecessary redundancy (duplicate data) to serve multiple applications       The data is stored so that they are independent of programs, which use the data. A common and control approach is used in adding the new data, modifying and retrieving existing data or deletion of data within the database A running database has function in a corporation, factory, government department and other organization. Database is used for searching the data to answer some queries. A database may be design for batch processing, real time processing or on line processing. DATABASE SYSTEM       Database System is an integrated collection of related files along...