COMP284 Scripting Languages
Lecture 1: Overview of COMP284
Handouts
Ullrich Hustadt
Department of Computer Science
School of Electrical Engineering, Electronics, and Computer Science
University of Liverpool
Introduction Motivation
How many programming languages should you learn?
1 Academic / Educational viewpoint:
Learn programming language concepts and
use programme languages to gain practical experience with them
– imperative / object-oriented — C, Java
– functional — OCaml, Haskell
– logic/constraint — Prolog, DLV
– concurrent — Go
then all (other) programming languages can be learned easily
2 An employer’s viewpoint:
Learn exactly those programming languages that the specific employer
needs
3 Compromise: Spend most time on 1 but leave some time for 2 to
allow more than one language from a class/paradigm to be learned
4 Problem: Which additional language do you cover?
; Look what is used/demanded by employers
COMP284 Scripting Languages Lecture 1 Slide L1 – 2
Introduction Motivation
Our domain
•
In this module we are particularly interested in scripting languages used
for the development of web-based applications
•
Web-based applications are client-server systems where
•
the client software, consisting of user interface and client-side logic,
runs in a web browser
•
the client software issues HTTP requests to a web server to retrieve
information or to update parts of itself
•
a web server acts as conduit for the HTTP requests from the client software
and the HTTP responses from the server software
•
the server software, implementing the server-side logic, handles the request
and produces a HTTP response, in the form of a HTML document or data
•
the server software often interacts with a database to produce its response
COMP284 Scripting Languages Lecture 1 Slide L1 – 3
Introduction Motivation
Websites and programming languages
Website Client-Side Server-Side Database
Google JavaScript,
TypeScript
C, C++, Go, Java,
Python, PHP,
BigTable, MariaDB
Facebook JavaScript Hack, PHP, Python,
C++, Java, . . .
MariaDB, MySQL,
HBase, Cassandra
YouTube Flash,
JavaScript
C, C++, Python, Java,
Go
BigTable, MariaDB
Yahoo JavaScript PHP MySQL, PostgreSQL
Amazon JavaScript Java, C++, Perl Oracle Database
Wikipedia JavaScript PHP, Hack MariaDB
Twitter JavaScript C++, Java, Scala, Ruby MySQL
Bing JavaScript C++, C# MS SQL Server
Wikipedia Contributors: Programming languages used in most popular websites. Wikipedia, The Free Encyclopedia,
11 December 2019, at 16:24. https://en.wikipedia.org/wiki/Programming_languages_used_in_most_popular_websites
[accessed 21 December 2019]
COMP284 Scripting Languages Lecture 1 Slide L1 – 4
Introduction Scripting languages
Scripting languages
PHP and JavaScript are scripting languages
Script
A user-readable and user-modifiable program that performs simple
operations and controls the operation of other programs
Scripting language
A programming language for writing scripts
Classical example: Shell scripts
#!/ bin / sh
for file in *; do
wc -l " $file "
done
Print the number of lines and name for each file in the current directory
COMP284 Scripting Languages Lecture 1 Slide L1 – 5
Introduction Scripting languages
Scripting languages: Properties
•
Program code is present at run time and starting point of execution
•
compilation by programmer/user is not needed
•
compilation to bytecode or other low-level representations
may be performed ‘behind the scenes’ as an optimisation
•
Presence of a suitable runtime environment is required for the execution
of scripts
•
includes an interpreter, or just-in-time compiler, or bytecode compiler plus
virtual machine
•
typically also includes a large collection of libraries
•
Executation of scripts is typically slower then the execution of code that
has been fully pre-compiled to machine code
#!/ bin / sh
for file in *; do
wc -l " $file "
done
COMP284 Scripting Languages Lecture 1 Slide L1 – 6
Introduction Scripting languages
Scripting languages: Properties
•
Rich and easy to use interface to the underlying operating system,
in order to run other programs and communicate with them
•
rich input/output capabilities, including pipes, network sockets, file I/O,
and filesystem operations
•
Easy integration within larger systems
•
often used to glue other systems together
•
can be embedded into other applications
#!/ bin / sh
for file in *; do
wc -l " $file "
done
COMP284 Scripting Languages Lecture 1 Slide L1 – 7
Introduction Scripting languages
Scripting languages: Properties
•
Variables, functions, and methods
typically do not require type declarations
(automatic conversion between types, e.g. strings and numbers)
•
Lots of pre-defined functions and libraries
•
Lots of pre-defined functions for the specific purpose
the language was designed for
•
Ability to generate, load, and interpret source code at run time
through an eval function
JavaScript:
var x = 2;
var y = 6;
var str = " if (x > 0) { z = y / x } else { z = -1 }";
con sole . log(' z is ', eval ( str )); // Output : z is 3
x = 0;
con sole . log(' z is ', eval ( str )); // Output : z is -1
COMP284 Scripting Languages Lecture 1 Slide L1 – 8
Introduction Scripting languages
Scripting languages: Properties
•
The evolution of a scripting language typically starts
with a limited set of language constructs for a specific purpose
Example: PHP started as set of simple ‘functions’
for tracking visits to a web page
•
The language then accumulates more and more language constructs
as it is used for a wider range of purposes
•
These additional language constructs may or may not fit well together
with the original core and/or may duplicate existing language constructs
•
During this evolution of the language, backward compatibility
may or may not be preserved
; Language design of scripting languages is often sub-optimal
COMP284 Scripting Languages Lecture 1 Slide L1 – 9
COMP284 Aims
Aims
1 To provide students with an understanding of
the nature and role of scripting languages
2 To introduce students to some popular scripting languages
and their applications
3 To enable students to write simple scripts using these languages
for a variety of applications
COMP284 Scripting Languages Lecture 1 Slide L1 – 10
COMP284 Learning outcomes
Learning Outcomes
At the end of the module students should be able to
1 develop server-side web-based applications
using an appropriate scripting language,
with emphasis on concurrent use of such applications
2 develop computer-based or client-side web-based applications
using an appropriate scripting language
COMP284 Scripting Languages Lecture 1 Slide L1 – 11
COMP284 Prerequisites
Prerequisites
•
COMP101 Introduction To Programming
Python
•
COMP122 Object-oriented Programming
Control structures, Object-oriented programming languages, Types,
Exceptions and exception handling, Graphical user interfaces,
Event-driven programming, Java
•
COMP107 Designing Systems For The Digital Society
Database design, SQL (Insert, Select, Update)
•
COMP207 Database Development
Transactions, SQL (Transactions)
•
HTML/CSS
COMP284 Scripting Languages Lecture 1 Slide L1 – 12
COMP284 Delivery
Delivery of the module: Lectures
•
Structure:
14 lectures
•
Schedule:
1–2 lectures per week spread over 9 weeks
See your personal timetable and e-mail announcements for details
•
Lecture notes and screencasts are available at
https://cgi.csc.liv.ac.uk.uk/
~
ullrich/COMP284/notes
•
Additional self study using the recommended textbooks
and the on-line material is essential
COMP284 Scripting Languages Lecture 1 Slide L1 – 13
COMP284 Delivery
Delivery of the module: Practicals
•
Structure:
– 1 practical to re-familiarise you with Linux
– 1 practical on HTML
– 4 practicals on PHP
– 3 practicals on JavaScript
•
All practicals involve working through exercises related to the previous
one/two lectures,
guided by a worksheet, with the help of demonstrators
•
Schedule:
1 practical per week for 9 weeks
Practicals start in week 1
•
Practicals assume familiarity with the related lecture material
COMP284 Scripting Languages Lecture 1 Slide L1 – 14
COMP284 Delivery
How to learn a new programming language
•
Once you know how to program in one programming language,
additional programming languages are best learned by a process of
enquiry and practice guided by existing experience
•
Typically, the questions that guide you are
•
What kind of . . . are there?
Example: What kind of control structures are there?
•
What is the syntax for . . . ?
Example: What is the syntax for conditional statements?
•
What happens if . . . ?
Example: What happens if 1 is divided by 0?
•
How do I . . . ?
Example: How do I catch an exception?
•
Talk to other people who are currently trying to learn the same
language or have already learned it
; Ask what has surprised them most
COMP284 Scripting Languages Lecture 1 Slide L1 – 15
COMP284 Delivery
How to learn a new programming language
•
Once you know how to program in one programming language,
additional programming languages are best learned by a process of
enquiry and practice
•
The best kind of learning is learning by doing
; The questions posed on the previous slide are often best explored
by experimenting with small sample programs (‘toy’ programs)
•
Work on substantive programs
; You need to convince employers that you have worked on programs
more substantive than ‘toy’ programs
; The assignments are ‘pretend’ substantive programs
but in reality are too small
•
Employers value experience, in particular, the experience that you get
from overcoming challenges
; Assignments that are not challenging are of limited value
COMP284 Scripting Languages Lecture 1 Slide L1 – 16
COMP284 Delivery
Delivery of the module: Office Hours and Announcements
•
Office hours
Fridays, 14:00 Ashton, Room 1.03
Fridays, 16:00 Ashton, Room 1.03
but always arrange a meeting by e-mail first
(U.Hustadt@liverpool.ac.uk)
•
Announcements will be send by e-mail
•
You should check you university e-mail account at least every other day
•
Always use your university e-mail account
if you want to contact me or any other member of staff
COMP284 Scripting Languages Lecture 1 Slide L1 – 17
COMP284 Delivery
Recommended texts
•
Core reading
•
R. Nixon:
Learning PHP, MySQL, & JavaScript: with jQuery, CSS & HTML5.
O’Reilly, 2018.
Harold Cohen Library: QA76.73.P224.N73.5 or e-book
•
Further reading
•
M. David:
HTML5: designing rich Internet applications, 2nd ed.
Focal Press, 2013.
Harold Cohen Library: QA76.76.H94.D24.2 or e-book
•
J. Niederst Robbins: Learning web design: a beginner’s guide to
HTML, CSS, Javascript, and web graphics.
O’Reilly, 2018.
Harold Cohen Library: e-book.
•
N. C. Zakas:
Professional JavaScript for Web Developers.
Wiley, 2009.
Harold Cohen Library: TK5105.888.J38.Z21.3 or e-book
COMP284 Scripting Languages Lecture 1 Slide L1 – 18
COMP284 Assessment
Assessment
•
This is a coursework-based module
(no exam)
•
Two assessment tasks need to be completed throughout the semester:
– PHP Deadline: Friday, 20 March, 10:00
– JavaScript Deadline: Friday, 24 April, 10:00
•
Effort required: about 15 hours each
(assuming you have kept up with lectures and practicals)
•
Available at: https://cgi.csc.liv.ac.uk/
~
ullrich/COMP284/
COMP284 Scripting Languages Lecture 1 Slide L1 – 19
COMP284 Assessment
Academic Integrity
•
Plagiarism occurs when a student misrepresents, as his/her own work,
the work, written or otherwise, of any other person (including another
student) or of any institution
•
Collusion occurs where there is unauthorised co-operation between a
student and another person in the preparation and production of work
which is presented as the student’s own
•
Fabrication of data occurs when a student enhances, exaggerates, or
fabricates data in order to conceal a lack of legitimate data
If you are found to have plagiarised work, colluded with others, or
fabricated data, then you may fail COMP284
Serious ‘offenders’ may be excluded from the University
Do not try to take a ‘shortcut’
You must do the work yourself!
COMP284 Scripting Languages Lecture 1 Slide L1 – 20
COMP284 Assessment
Academic Integrity: Lab rules
•
Do not ask another student to see any part of their code for a
COMP284 assignment
; contravention of this leads to collusion
•
Do not show or make available any part of your code relating for a
COMP284 assignment to any other student
; contravention of this leads to collusion
•
Do not share (links to) on-line material that might help with a
COMP284 assignment
; contravention of this leads to collusion
•
Lock your Lab PC when you leave it alone
•
Where you use any material/code found on-line for a COMP284
assignment, you must add comments to your code indicating its origin
by a proper academic reference
; contravention of this is plagiarism
; acknowledged code re-use may still result in a lower mark
COMP284 Scripting Languages Lecture 1 Slide L1 – 21
COMP284 Background Reading
Background Reading
Over the next four weeks, read
•
Part I: Getting Started
•
Part II: HTML for Structure
•
Part III: CSS for Presentation
of J. Niederst Robbins: Learning web design:
a beginner’s guide to HTML, CSS, Javascript, and web graphics.
O’Reilly, 2018.
COMP284 Scripting Languages Lecture 1 Slide L1 – 22
