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.
Types of Computer Networks Computer networks are categorized according to: How they are organized physically. The way they are used. The distance over which they operate. Three main types of computer networks are as follows: LAN (Local Area Network) WAN (Wide Area Network) MAN ( Metropolitan-Area Network) LAN (Local Area Network) LAN is the most common type of network . LAN stands for Local area Network . It covers a small area. Most LANs are used to connect computers in a single building or group of buildings. Hundreds or thousands of computer maybe connected through LAN. Typical LANs can be found in industrial plants, office buildings, and college or university campuses. LANs are capable of transmitting data at very fast rate. Data transmission speeds of LAN are 1 to 100 megabits per second. It is much faster than data transmission over a telephone line. LAN can transmit data in a limited distance. There is also a limit on the number of...
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