Date: Wed, 16 Feb 2011 18:23:46 -0600 (CST) From: Mark Jacobson To: 810-023-01-spring@uni.edu Subject: Microcomputer Systems 023 StudioIT 1 ITT 134 lab Thursday... Hello 023 9:30 TTh students, Here are the two topics we covered on Tuesday in class: 1. PERL and CGI example for generating random quotes or random web page every time you visit or refresh, and 2. Hamming codewords for error detection/correction. ASCII codes - 8 binary digit code for each keyboard character - "0" = 48, ..., "9" = 57, ..., "A" = 65, "Z" = 90 "a" = 97. ----------------------------------------------------------------------- PERL - Practical Extraction and Report Language and server side coding. The CGI - Common Gateway Interface model. ----------------------------------------------------------------------- http://www.cs.uni.edu/~jacobson/23/perlquotes.html and it has links to these pages: http://www.cs.uni.edu/~jacobson/23/PERL_CGIquotes.pdf http://www.uni.edu/jacobson/cgi/rand.cgi .CGI http://www.uni.edu/jacobson/cgi/randomAll.cgi .CGI Look over these examples from 810:023 students from one year ago. http://www.cs.uni.edu/~jacobson/23/perl.html As you know from class, for the .CGI files, you need to click the REFRESH button on your web browser to see another randomly chosen quote. Only other concept, the avalanche concept and using PERL to encrypt passwords. ----------------- http://www.cs.uni.edu/~jacobson/23/encript3.out ASCII encoding of character data - the ASCII code for A is: 01000001 = A = 65 01000010 = B = 66 01000011 = C = 67 a = 65 + 32 = 97 01000001 = 65 100000 = 32 -------- ---- 01000001 = 97 ASCII = American Standard Code for Information Interchange The interchange is between humans and computers. ------ ---------- A-Z 0 and 1 a-z BINARY {} () [ ] , ; : ! 0 1 ... 9 ------------------------------------------------------------------------ PERL - Practical Extraction and Report Language and server side coding. The CGI - Common Gateway Interface model. The above is a reading assignment. Please study the given URLs and try out the software. Take notes. Expose yourself to the PERL and to the UNIX (ls, cat, more, cd, ls -l, chmod, cat -vet, ... ------------------------------------------------------------------------ ------------------------------------------------------------------------ EVEN Parity, Odd Parity, Hamming codewords use EVEN parity and send 12 bits = 8 bits of data, and 4 bits of error detection information. ------------------------------------------------------------------------ Hamming codewords: This page was handed out. We showed how EVEN and ODD parity works. Then we covered how 01000001, the letter "A", would be send out over the internet if the Hamming error detection/correction protocol was being used. http://www.cs.uni.edu/~jacobson/hamming.html ------------------------------------------------------------------------