Found 1304 Articles for MCA

EER is a high-level data model that incorporates the extensions to the original ER model. Enhanced ERD are high level models that represent the requirements and complexities of complex database.In addition to ER model concepts EE-R includes −Subclasses and Super classes.Specialization and Generalization.Category or union type.Aggregation.These concepts are used to create EE-R diagrams.Subclasses and Super classSuper class is an entity that can be divided into further subtype.For example − consider Shape super class.Super class shape has sub groups: Triangle, Square and Circle.Sub classes are the group of entities with some unique attributes. Sub class inherits the properties and attributes from ... Read More

Coaxial cables, commonly called coax, are copper cables with metal shielding designed to provide immunity against noise and greater bandwidth. Coax can transmit signals over larger distances at a higher speed as compared to twisted pair cables.Structure of Coaxial CablesCoax has a central core of stiff copper conductor for transmitting signals.  This is covered by an insulating material. The insulator is encased by a closely woven braided metal outer conductor that acts as a shield against noise. The outer conductor is again enclosed by a plastic insulating cover. The structure is shown in the following figure −Categories of Coaxial CablesCoaxial ... Read More

The primary purpose of computer networks is to transfer data from a source machine to a destination machine. One of the elementary ways to transfer data between machines is to use removable storage media. The steps for the transfer are −Copy data from the source computer to the removable storage device.Physically transport the removable device to the source computer.Copy data from the removable device to the destination computer.Some of the removable media that can use for transferring data between devices are −Magnetic tapesOptical discs like CDs, DVDs, and Blu-ray DiscsUSB flash drivesZip discs and floppy discsMemory cards and Memory sticksAdvantages ... Read More

The transmission medium can be defined as a pathway that can transmit information from a sender to a receiver. Transmission media are located below the physical layer and are controlled by the physical layer. Transmission media are also called communication channels.Transmission media are of two types −Guided Transmission MediumUnguided Transmission MediumThe following chart categorizes transmission media −Guided Transmission MediumGuided transmission media are also called bounded media or wired media. They comprise cables or wires through which data is transmitted. They are called guided since they provide a physical conduit from the sender device to the receiver device. The signal traveling ... Read More

Bandwidth The range of frequencies that are used for transmitting a signal without being substantially attenuated is called the bandwidth. It is calculated as the difference between the highest and the lowest frequencies. It is expressed in Hertz (Hz).For example, if the minimum frequency is 100 Hz and the maximum frequency is 1000 Hz, the bandwidth will be 900 Hz.The bandwidth of a transmission medium is the frequency width of the medium and is dependent upon its physical characteristics like thickness, material, length etc. For example, the bandwidth of a coaxial cable is 750 MHz ( MegaHertz).BasebandBaseband transmissions are those requiring ... Read More

In a Relationship, Participation constraint specifies the existence of an entity when it is related to another entity in a relationship type. It is also called minimum cardinality constraint.This constraint specifies the number of instances of an entity that can participate in a relationship type.There are two types of Participation constraint −Total ParticipationEach entity in the entity set is involved in at least one relationship in a relationship set i.e. the number of relationship in every entity is involved is greater than 0.Consider two entities Employee and Department related via Works_For relationship. Now, every Employee works in at least one ... Read More

In Ternary relationship three different Entities takes part in a Relationship.Relationship Degree = 3For Example: Consider a Mobile manufacture company.Three different entities involved:Mobile - Manufactured by company. Part - Mobile Part which company get from Supplier. Supplier - Supplier supplies Mobile parts to Company.Mobile, Part and Supplier will participate simultaneously in a relationship. because of this fact when we consider cardinality we need to consider it in the context of two entities simultaneously relative to third entity.Cardinality in Ternary RelationshipSay for a given instance of Supplier and an Instance of Part, can that supplier supply that particular part for multiple Mobile models.Example ... Read More

A Binary Relationship is the relationship between two different Entities i.e. it is a relationship of role group of one entity with the role group of another entity.There are three types of cardinalities for Binary Relationships −1. One-to-One2. One-to-many3. Many-to-ManyOne-to-OneHere one role group of one entity is mapped to one role group of another entity. In simple terms one instance of one entity is mapped with only one instance of another entity.In this type the primary key of one entity must be available as foreign key in other entity.For example − consider two entities Person and Driver_License.Person has the information about ... Read More

A One-to-Many Unary Relationship is the association with the same entity between the same instances represented by different role groups.Consider the relationship between Managers and Employees.The two different Roles in this relationship are- Managers and Employees. Only few Employees take the role of Managers within an organization while everyone working for an organization is an Employee.One Manager manages multiple Employees and each Manager is also an Employee. One-to-Many Optional-MandatoryEach instance of one role group must participate in the relationship while instance of other role group can optionally participate in the relationship. The Role of Manager satisfies the optional participation as there are ... Read More

A One-to-One Unary Relationship is the association with the same entity between the same instances represented by same role group.Above figure represents a set of married persons with the relationship MARRIED_TO. Each person is married to only one and only one person in the group.In One-to-One Unary we have three cases available −Mandatory-MandatoryOptional-OptionalOptional-Mandatory or Mandatory-OptionalMandatory-MandatoryEach instance of the role group must fully participate in the relationship. In the above example a Person is married to one and only one Person.Optional-OptionalIn this case the participation of a instance within a role group is optional i.e. the participation is not mandatory.In the ... Read More