LBSC 690 Session 4 Programming Languages How do

LBSC 690 Session 4 Programming

Languages How do we learn a language? Learn by listening Then reading Then writing How do we teach programming? Learn to write first Contributes to programming problems

Programming Languages Programs are written in a programming language. Two types: Procedural and non-procedural (declarative). Are artificial languages.

Artificial Languages Consist of: A set of symbols (an alphabet) A vocabulary Controlled segment (an authority list) A user-defined segment Syntax Semantics

Levels of Languages “Low” to “high” Machine language Lowest level All languages must be translated into this to run on the computer Unique to each platform Next level: Assembler

Levels (Cont’d) Higher Level Languages: Basic, Pascal, C, Fortran, Cobol, Visual Basic, Visual C, etc. Fourth Generation Languages: NOMAD, QBE, etc. Object Oriented Languages: Smalltalk, C++, Java.

Software Tools Facilitate writing programs: Compilers & Interpreters. Software Development Environments.

Anatomy of a Web Presentation A collection of one or more Web pages The Web Site A server on the Internet containing one or more Web presentations A Web page An HTML (Hyper. Text Markup Language) document, consisting of text and tags. Has a. html or. htm extension Home page Entry point for a Web presentation

What is HTML? Hyper. Text Markup Language. Based on Standard Generalized Markup Language (SGML). Developed by Tim Berners-Lee Describes the structure of a document. Not its presentation. Does not describe page content. Designed to be used cross-platform. A web browser interprets and displays HTML documents

HTML is a Markup Language Start with text and add special tags around words and paragraphs. Tags indicate different parts of a page and produce different effects in the browser. HTML has a given, defined set of tags. Users cannot create their own.

HTML Versions HTML 2. 0. Base set of tags. HTML 3. 2. Second release. HTML 4. 0. Current generation. Includes new features for flexibility. HTML 4. 01. Has corrections for 4. 0.

What do HTML Files look like? Contain: Text of page itself, Special instructions called HTML tags indicating page elements, structure, formatting and hypertext links to other pages or to included media. Look at HTML sources. Display the HTML source code.

Viewing HTML Source Code 1. Start your Web browser 2. Display the Web page you want to view 3. Click “View” 4. Click “Source” (In Netscape click “Page Source”

Assignment 2: Creating Web Site Use a text editor. Saves files in ASCII format. In Unix, pico is a text editor, In Windows, Notepad and DOS Edit are text editors. View your created pages with browser. Create a Web site in your public WAM directory. View it again.

Tags Each HTML tag gives a specific instruction or command requires beginning and ending angle brackets (not case sensitive): Most tags have an opening and a closing tag: For example: <HTML> Text </HTML> {The forward slash indicates the end. }. This tag identifies the content of this file as a Web page.

Tags (Cont’d. ) <HEAD> & </HEAD> tag: Specifies that the lines in it are prologue, e. g. , the title: <TITLE> & </TITLE> <BODY> & </BODY> tags: Encloses the remainder of the text and other contents (links, pictures, etc). <P> & </P> tags: Indicates beginning & end of a new paragraph. <BR>: Indicates start of a new line. (No</BR>).

Tags (Cont’d). Blank spaces require special codes; “&nbsp” Headings are used to divide and organize sections of text. (Can be up to 6 levels). <H 1> &</H!> up to <H 6> & </H 6>. To use preformatted text, e. g. , tables: <PRE> & </PRE>.

TAGS (Cont’d. ) To add comments use the Comments tag: . Certain tags have attributes: E. g. , <BODY TEXT=“BLUE”>

LISTS HTML defines different kinds of lists: Ordered: <OL> &</OL>. Each list item is indicated by <LI>. Unordered (bulleted) lists: <UL> &</UL>. Glossary lists: <DL>. NOTE: Nested lists can be created.

IMAGES Can be added to Web pages Tag is: <IMG SRC=“? ”> where “? ” specifies location of image on your computer. Should use GIF or JPEG images. Thumbnail images Can be used in background.

LINKS Can create links: To other pages on the Web: <A HREF=“? ”>. Within a Web page: <A NAME=“? ”>. Links to images: <A HREF=“? ”>. Links to E-mail: <A HREF=mailto: ? >. Also links to Files and FTP sites. NOTE: Must add </A> after above tags.

OTHER CAPABILITIES Create Tables Create Forms Create Frames Divide browser windows into sections, each displaying a different Web page. Create Advanced Web Pages Use of Java. Script & Java Applets

Cascading Style Sheets Are used to define formatting and layout of information on Web pages For a single page or multiple pages Can specify formats in one central location Provides greater capability than using individual tags on each page. Can focus use on specific elements: classes

Sources of Help for HTML Specifications: www. w 3. org/TR/hrml 401/cover. html. A Beginner’s Guide to HTML: www. ncsa. uiuc. edu/General/Internet/WWW/ HTMLPrimer. html. Laura Lemay, Teach yourself Web Publishing with HTML 4 in a Week, Fourth Edition, Sams. Net. 1997. Ed Tittel, HTML for Dummies, IDG Books, 1997.