1 Copyright © 2002 Pearson Education, Inc.

2 Chapter 1 Introduction to Perl and CGI

3 Copyright © 2002 Pearson Education, Inc. World Wide Web Background l The World Wide Web (WWW) is a collection of millions of documents and files that are accessible via the Internet l Web browsers are special computer programs that know how to retrieve and display files from the World Wide Web. Can work with Play a file in the wav format (a sound file) Interpret and then display a file in a gif format ( a digital picture file) Interpret and then display a file in the HTML format (a text-based Web page)

4 Copyright © 2002 Pearson Education, Inc. Accessing HTML Files Over the Internet

5 Copyright © 2002 Pearson Education, Inc. HTML? l The Hypertext Markup Language (HTML) uses coded commands called HTML tags that provide instructions to Web browsers indicating how to display each page

6 Copyright © 2002 Pearson Education, Inc. Displaying HTML

7 Copyright © 2002 Pearson Education, Inc. Web Application Program l Carries out many dynamic tasks, such as the following: »Input a search term, search the WWW, and return the results »Calculate and display the number of times that a page has been viewed »Verify the input fields on a Web form »Save a Web form into a database »Display a special graph, or return the results of a calculation based on data input from a form

8 Copyright © 2002 Pearson Education, Inc. The Common Gateway Interface l a standard that enables Web browsers to exchange data with computer programs located on a Web server l first appeared in the NCSA HTTPD Web server software built by the National Center for Super- computing Applications (NCSA). »one of the first widely used Web servers »was simple and the program source code was made available for free l It is simple to use and available on a variety of Web servers.

9 Copyright © 2002 Pearson Education, Inc. How Browsers and Web Applications Work with CGI

10 Copyright © 2002 Pearson Education, Inc. An Interface with Different Programming Languages l Web application programs that are developed specifically to work with the CGI standard are known as CGI programs. l Lots of different programming languages can be used. For example, »Perl, »Visual Basic, »Java, »C, » C++, » and UNIX shell scripts.

11 Copyright © 2002 Pearson Education, Inc. The Perl Programming Language l Practical Extension and Reporting Language »invented in 1987 by Larry Wall at NASAs Jet Propulsion Laboratory »developed as a utility programming language for the UNIX operating system »gained popularity because of its ease of use, free availability via the Internet, and its powerful combination of

12 Copyright © 2002 Pearson Education, Inc. Why Perl is Popular l Perl is a free language with lots of free applications l Perl is easier to work with than many other languages l Perl provides a CGI interface module l Perl applications are portable.

13 Copyright © 2002 Pearson Education, Inc. Why Perl is Popular l Perl is a free language with lots of free applications l Perl is easier to work with than many other languages l Perl provides a CGI interface module l Perl applications are portable.

14 Copyright © 2002 Pearson Education, Inc. Internet Service Provider Issues l Some things to determine with your ISP »Allow CGI programs to execute on its Web- server? Does it have Perl? What Version? »Login and initial password on the Web server? »Where do you put your Perl programs on the Web server and what permission settings? »How much disk space for publishing? »Support FTP and/or Telnet access?

15 Copyright © 2002 Pearson Education, Inc. FTP Vs Telnet Access

16 Copyright © 2002 Pearson Education, Inc. Summary l Web pages written in HTML are static and cannot interact with users. l CGI is an interface standard that allows computer programs to communicate with Web servers. Several programming languages can be used with CGI.

17 Copyright © 2002 Pearson Education, Inc. Summary - II l Perl is a popular computer language that can be used for developing CGI programs. l You can install Perl and your own Web server software on your PC or workstation. l If you use an ISPs Web server, find out several things about its services.