Computer Science – CE -2013 - Section C

7/29/2019 Computer Science CE -2013 - Section C

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Databases Management Web Programming

Computer Graphics


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A database is a structured collection of data The term database is correctly applied to the

data and their supporting data structures,and not to the database management system(DBMS).

The database data collection with DBMS iscalled a database system.


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Well known DBMSs include Oracle

FoxPro IBM DB2

Linter

Microsoft Access

Microsoft SQL Server MySQL

PostgreSQL and SQLite.


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Database concept The database concept has evolved since the 1960s

to ease increasing difficulties in designing,building, and maintaining complex informationsystems (typically with many concurrent end-users, and with a large amount of diverse data).

Though the terms database and DBMS definedifferent entities, they are inseparable: adatabase's properties are determined by itssupporting DBMS.


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Evolution of database and DBMS technology The introduction of the term database coincided with the

availability of direct-access storage (disks and drums) fromthe mid-1960s onwards

The term represented a contrast with the tape-basedsystems of the past, allowing shared interactive use ratherthan daily batch processing.

In the period since the 1970s database technology haskept pace with the increasing resources becomingavailable from the computing platform: notably the rapidincrease in affordable capacity and speed of disk storage,and of main memory.

This has enabled ever larger databases and higherthroughput to be achieved.


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Active database Cloud database

Data warehouse Distributed database Document-oriented database Embedded database


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Early data models

Hierarchical model

Network model

Inverted file model

Relational model

Object model


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Database languages are dedicatedprogramming languages, tailored and utilizedto define a database (i.e., its specific data types and

the relationships among them),

manipulate its content (e.g., insert new data

occurrences, and update or delete existing ones),and

query it (i.e., request information: compute andretrieve any information based on its data).


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The external level defines how each end-user type understands the organization of its

respective relevant data in the database, i.e., the different needed end-user views. A single

database can have any number of views at the external level.

The conceptual level unifies the various external views into a coherent whole, global view.

It provides the common-denominator of all the external views. It comprises all the end-user

needed generic data, i.e., all the data from which any view may be derived/computed. It isprovided in the simplest possible way of such generic data, and comprises the back-bone of

the database. It is out of the scope of the various database end-users, and serves database

application developers and defined by database administrators that build the database.

The internal level (or physical level) is as a matter of fact part of the database

implementation inside a DBMS (see Implementation section below). It is concerned with

cost, performance, scalability and other operational matters. It deals with storage layout of

the conceptual level, provides supporting storage-structures like indexes, to enhance

performance, and occasionally stores data of individual views (materialized views),

computed from generic data, if performance justification exists for such redundancy. It

balances all the external views' performance requirements, possibly conflicting, in attempt

to optimize the overall database usage by all its end-uses according to the database goals

and priorities.


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Access control Data security

Database audit


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Every database transaction obeys thefollowing rules:

Atomicity Consistency

Isolation

Durability
http://en.wikipedia.org/wiki/Atomicity_(database_systems)http://en.wikipedia.org/wiki/Database_Consistency_(computer_science)http://en.wikipedia.org/wiki/Isolation_(database_systems)http://en.wikipedia.org/wiki/Durability_(computer_science)http://en.wikipedia.org/wiki/Durability_(computer_science)http://en.wikipedia.org/wiki/Isolation_(database_systems)http://en.wikipedia.org/wiki/Database_Consistency_(computer_science)http://en.wikipedia.org/wiki/Atomicity_(database_systems)


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Programming is the intricate art of telling acomputer what to do.

Programming allows you to make newsoftware and have the computer do newthings.

Web site programming is the same exceptyou write applications or web pages that areused by a web browser.


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HTML is written in the form of HTMLelements consisting of tags enclosed in angle

brackets (like ), within the web pagecontent. HTML tags most commonly come in pairs like

and

Unpaired Tags e.g. , ,
,


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It is simply a method or protocol (a very oldone) for interfacing external applications withservers

The NCSA describes CGI as follows: A plain HTML document that the Web daemon

retrieves is static, which means it exists in a

constant state: a text file that doesn't change. ACGI program, on the other hand, is executed inreal-time, so that it can output dynamicinformation.


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A CGI application can be written in almost anyprogramming language but most commonly Perl is used. Once the program is written it needs to be put in a special folder

where external programs, like your web browser, can access it.

It will carry out its action, like getting information from adatabase, and then return information back to your browser.

CGI is supported on almost any platform, Windows orLinux variants

CGI can be used for managing email, connecting to otherweb sites or servers, processing form information, storinginformation in a database, creating cookies in a webbrowser, and just about anything else.


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The following CGI program shows all theenvironment variables passed by the web

server:


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Perl borrows features from other programming languagesincluding C, shell scripting (sh), AWK, and sed. The language provides powerful text processing facilities

without the arbitrary data-length limits of many contemporary

Unix tools, facilitating easy manipulation of text files. Perl gained widespread popularity in the late 1990s as a CGI

scripting language, in part due to its parsing abilities. In addition to CGI, Perl is used for

graphics programming

system administration network programming

Finance

bioinformatics and other applications.


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In older versions of Perl, one would write the Hello World program as:

print "Hello World!\n";

use5.010; say "Hello World!";

In later versions, which support the say statement, one can also write it as:use 5.010;

say "Hello World!";

Good Perl practices require more complex programs to add the use strict; and usewarnings; pragmas, leading into something like:

use strict;

use warnings;

print "Hello World!\n";

$ perl -i.bak -lp -e 's/Bob/Robert/g' *.txt


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Here is a more complex Perl program, that counts down the seconds up to a giventhreshold:

#!/usr/bin/perl

use strict;use warnings;my ( $remaining, $total );$remaining = $total = shift(@ARGV);STDOUT->autoflush(1);while ( $remaining ) {

printf ( "Remaining %s/%s \r", $remaining--, $total );sleep 1;}print "\n";


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The user interface, in the industrial design field ofhumanmachine interaction, is the space whereinteraction between humans and machines occurs.

The goal of interaction between a human and amachine at the user interface is effective operationand control of the machine, and feedback from themachine which aids the operator in makingoperational decisions.

Examples of this broad concept of user interfaces includethe interactive aspects of computer operating systems,hand tools, heavy machinery operator controls, andprocess controls. The design considerations applicablewhen creating user interfaces are related to or involvesuch disciplines as ergonomics and psychology.


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A user interface is the system by which people (users)interact with a machine. The user interface includeshardware (physical) and software (logical) components. User

interfaces exist for various systems, and provide a means of: Input, allowing the users to manipulate a system

Output, allowing the system to indicate the

effects of the users' manipulation


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Direct manipulation interface is the name of a general class of user interfaces that allowusers to manipulate objects presented to them, using actions that correspond at leastloosely to the physical world.

Currently (as of 2009) the following types of user interface are the most common: Graphical user interfaces (GUI) accept input via devices such as computer

keyboard and mouse and provide articulated graphical output on the

computer monitor. There are at least two different principles widely used in GUI design: Object-oriented

user interfaces (OOUIs) and application oriented interfaces.

Web-based user interfaces or web user interfaces (WUI) that accept inputand provide output by generating web pages which are transmitted via theInternet and viewed by the user using a web browser program. Newerimplementations utilize Java, AJAX, Adobe Flex, Microsoft .NET, or similar

technologies to provide real-time control in a separate program, eliminatingthe need to refresh a traditional HTML based web browser. Administrative web interfaces for web-servers, servers and networked computers

are often called control panels.

Touchscreens are displays that accept input by touch of fingers or a stylus.Used in a growing amount of mobile devices and many types of point of sale,industrial processes and machines, self-service machines etc.


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a web site as the Front Office or Showroom software and the webapplication as the Back Office software.

Other people may use Front End and Back End. The front office is where visitors come in to browse and sometimes

make a purchase. The back office is there to provide support services for the front office,

such as processing customer orders and maintaining, issuing andreplenishing inventory.

While the front office is open to anyone, access to the back office isrestricted to authorised personnel only.

While the front office software is web only, the back office softwarecan be either desktop or web, or a mixture of the two.

It is possible for a web site (front end) to have a companion webapplication (back end), as shown in the following diagram:


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Computer Science – CE -2013 - Section C

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