Computer Science UGC Net

Computer Network means an interconnected collection of autonomous computers. Two computers are said to be interconnected if they're able to exchange information and they use transmission media like copper, fibre optics , microwave etc. Features of Computer Networks : 1) Resource sharing 2) High reliability 3) Saving Money 4) Scalability 5) Communication Medium Uses of Computer networks : 1) For people, video conferencing, person to person communication through computer network. 2) Accessing for remote information 3) For interactive entertainment like video on demand and playing game. 4) It is used for social issues. Data communication: Data communication based transfer data from one point to another and in other words data communication means of transport data from source to destination. The data is transmitted from source to destination through a transmission medium in a form of electromagnetic waves. The transmission medium either guid...

Database :  It is a collection of related data that contains information about one particular enterprise. DBMS ( Database Management System):  It is a software system that allows data contained in a database. The objective of DBMS is to provide an easy method of defining, storing and retrieving information contained in database. Characteristics of database approach : In the database approach a single repository of data is maintained that is define once and then accessed by various users. In file systems, each application is free to name that are elements independently. In contrast in a database the names or levels of data define once and used used repeatedly by queries, transactions, applications. The main characteristics of database approach versus the file processing approach are the following: Self describing nature of a database system Insulation between programs and data, data abstraction Support of multiple views of the data Sharing of data and multi user tr...

A compiler is a program that reads a program written in one language, the source language and translate into an equivalent program in another language that is target language.                                 C ompiler view Compilers are sometimes classified as single pass, multi pass, load-and-go, debugging or optimising, depending on how they have been constructed. Bootstrap compiler : For bootstrapping, a compiler is characterized by 3 languages; the source language "S" that compile the target language "T" that generates code for and implementation language "I" that it is written in. We represent them using following diagram: Phases of a compiler: conceptually compiler operates in phases, each of which transforms the source program from one representation to another.  the first three pages from the bulk of the analysis portion of a compiler. Lexical analysis: in a com...

Propositional or boolean logic: Basically logics are of two types; propositional logic and predicate logic. Proposition is an assertion which is either true or false but cannot be both at same time. Eg: 1. 3+4=7 2. 19 is a prime number 3. Earth is rectangular in shape In this statement 1 and 2 are proposition but 3rd is not bcoz it's false statement. This is assertion not proposition and this is called linear paradox. Basic logic operations on proposition: 1.)Conjunction: Let p and q are two propositions.Conjunction is described by a word " and" . Truth table for and gate is:   2. Disjunction: it is described by "or" . Truth table for or is: 3. Negation: It is represented by tilde ~. Truth table is: 4. Implication: Represented by =>.                     

"An Operating System is an interface between the computer user and the computer hardware". An operating system is an program that manages the computer hardware.Basically, a computer system can be divided roughly into four components the hardware the operating system the application programs and the users. It controls and coordinate the use of hardware among the various application programs for various users. We have various operating systems available. Some popular operating system are: Linux, Unix, windows operating system which is mostly used these days, MAC operating system (specifically used by "apple"). Main Functions of Operating System: 1. Process management 2. Main Memory management 3. File management 4. Input/Output management 5. Secondary storage management Process Management: A program is a passive entity such as content of a file stored in disk, whereas a process is an active entity, with a program counter specifying the ne...