Basics of scripting language,difference between script and program and its kind

1. BY
SANA MATEEN
6/13/2016 1Introduction to scripts and scripting

2. INTRODUCTION TO SCRIPTS AND SCRIPTING
 Script is a program written for special runtime environment that automate the
execution of tasks.
 Scripting is the action of writing scripts using scripting language.
 Scripting Language are used to extend the functionality of software . For
example enhancing web pages by providing dynamic content.
 They are designed to automate frequently used task that usually involve calling
or passing commands to external program.
Examples:
1. PERL- PRACTICAL EXTRACTION AND REPORT LANGUAGE
2. PHP-Hypertext Preprocessor(Personal Home Page)
3. TCL-Tool Command Language and PYTHON
TCL
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3. SCRIPTING VS. PROGRAMMING: IS THERE A DIFFERENCE?
Scripting Programming
 Scripts are interpreted . It means
they are processed from scratch
every time you run them.
 Programs are executed.
Problems addressed by Scripting language
 Building applications from off-the-shelf components.
 Example:
Use of Visual Basic to develop GUI using prebuilt Visual Controls.
 Controlling applications that have a programmable interface(protocols
to be followed while building a software).
 Speed of development is more important than runtime efficiency.
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4. ORIGIN OF SCRIPTING
 The UNIX O.S developers coined the term shellscript for sequence of commands
that were read from a file and followed in sequence.
 Script is a file that is intended to be executed directly rather than being compiled.
 Examples of scripts with respect to unix system are:
 AWK: This utility reads the standard input line by line and takes an action on part of
entire line.
 These actions are specified in awk script that consist of list of instructions.
 Perl: is a scripting language developed by Larry Wall, especially designed for text
processing.
 Though Perl is not officially an acronym but many times it is used as it stands
for Practical Extraction and Report Language.
 It runs on a variety of platforms, such as Windows, Mac OS, and the various versions
of UNIX.
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5. ORIGIN OF SCRIPTING
 In DOS(Disk Operating System), use of dial up connection to remote system
require scripts that automate the sequence of operation required to establish a
connection to remote system.
 Use rasphone( Remote Access Phonebook) command.
 Another occurrence of script was in Apple Macintosh HyperCard Application,
which is one of the Hypertext system.
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6. SCRIPTING TODAY
 Scripting allows application to be developed much faster than traditional
methods allow.
 We can use it to manipulate,customize,automate the facilities of existing
system.
 Eg: Use of client side scripting and Dynamic HTML to create interactive and
feature rich enhanced web pages.
 Using Scripting Language with its rich functionality .These are used by UNIX
admin for System maintenance work, like managing user permissions.
 Windows system admin adopt Perl for their work.
 Apache web server has an embedded Perl interpreter for CGI scripts
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7. CGI SCRIPT ISAPI TECHNOLOGY
 CGI stands for Common Gateway
Interface.
 It defines a standard way in which
information may be passed to and
from the browser and server.
 CGI scripts can be written using
PERL.
 ISAPI stands for Internet Server
Application Program Interface
technology . It is set of window program
calls that let you write a web server
application that will run faster than CGI.
 We can create Dynamic Link Library
application file using this technology.
 We can write an ISAPI script in any
language that will create an executable
object on your system. For example, C++,
Visual Basic, or Perl script on Windows.
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8. CHARACTERISTICS OF SCRIPTING LANGUAGE
 Integrated Compile and Run
Scripting Language behave as if they were interpreted. They are often an
interactive, experimental activity that doesn’t fit well with the “edit-compile-
link-run” cycle of conventional programming.
A few Scripting Languages like Unix Shell and TCL(Tool Command
Language) version 7 are indeed implemented as strict interpreters.
However most of the languages in current use opt for hybrid technique
which involve compiling to an intermediate form which is then
interpreted.
 Low Overhead and ease of use
Based on the usage variables can be declared and initialized . Later
focus was on explicit variable declaration, which requires that you declare every
variable before you use it.
Eg: Dim sum As Integer (or) sum=10;
 Enhanced Functionality
Most of the languages provide powerful string manipulation based on
the use of regular expression(A regular expression is a string of characters that
define the pattern or patterns you are viewing. ). Some languages support easy
access to API or Object model exported by application.
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9. CHARACTERISTICS OF SCRIPTING LANGUAGE
 Efficiency is not an issue
Ease of use is achieved at the expense of efficiency
eg: interpretation rather than compiling
Focus is not on high performance but on the speed of development together
with ability to make changes to meet new requirement.
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