COMPSCI 111 / 111G Mastering Cyberspace: an Introduction to Practical Computing Software Is Loaded CPU Executes Instruction

Instructions for the computer • Loaded from Secondary Storage into Primary Memory • Runs (executes) from RAM COMPSCI 111 / 111G Mastering Cyberspace: An introduction to practical computing Software is loaded CPU executes instruction

Hard Disk RAM Read / Write CPU Software

http://en.wikipedia.org/wiki/Software 21/07/2006 COMPSCI 111/111G - Lecture 03 1 21/07/2006 COMPSCI 111/111G - Lecture 03 2

File Formats Standards

All data is stored as numbers Open Standard • Method of encoding depends on the software • Published publicly • Free to use File Formats • Maintained by a "non-profit" organisation • Defines the way that the numbers are interpreted

File Extensions Proprietary Standard • A dot followed by letters at the end of a file name • Intellectual property of an entity (individual / company) • Windows OS uses the file extension to determine the file format • Use of the standard is usually through license • Also used to decide which application to use to open the file

21/07/2006 COMPSCI 111/111G - Lecture 03 3 21/07/2006 COMPSCI 111/111G - Lecture 03 4 Kinds of Software Copyright and Patents

System Software Software subject to normal legal copyright • Needed to run the computer system • Creator retains the rights to their creations • Operating System, Device Drivers, Diagnostic and maintenance tools Software Patents Application Software • Retain control over ideas / inventions • Helps the user complete a task • US recognises software Patents, Europe does not • Word Processor, Spreadsheet, Database, Web Browser, Games • Hotly debated issue

21/07/2006 COMPSCI 111/111G - Lecture 03 5 21/07/2006 COMPSCI 111/111G - Lecture 03 6

Freeware Shareware

Software is distributed free of charge Trial period offered • No agreement about distribution, access to source code • Purchase the license and upgrade to commercial version

Types of Freeware Nagware • Loss Leader • Reminder messages to license software •Adware • Donationware Crippleware • Postcardware • Software lacks the advanced features until licensed • E.g. Word processor that cannot Save or Print Abandonware • Not legally recognised

21/07/2006 COMPSCI 111/111G - Lecture 03 7 21/07/2006 COMPSCI 111/111G - Lecture 03 8 Proprietary Software Open Source / Free Software

Software that has restrictions on using and copying Free Software • All rights are retained by the owner. • Freedom to use and study the work • Owner enforces these restrictions • Freedom to copy and share the work with others • Freedom to change the work Can be: • Freedom to distribute changed and therefore derivative works •Commercial • Shareware Copyright prevents these acts • Semi-free (use for non-profit) • Explicit permission is required • Free software license gives permission

Richard Stallman • Free Software Foundation (FSF) • GNU General Public License (GPL) •Copyleft

http://en.wikipedia.org/wiki/Copyleft 21/07/2006 COMPSCI 111/111G - Lecture 03 9 21/07/2006 COMPSCI 111/111G - Lecture 03 10

Operating System Command Line Interface

Low-level software that allows you to use the system Text-based • Default interface when no application is running •Powerful • Manages the system, Schedules tasks, manages memory • Hard to use • Interact with the hardware • Good for experts

Examples: • Microsoft Windows • Macintosh OS • Linux

http://en.wikipedia.org/wiki/Operating_system http://en.wikipedia.org/wiki/Command_line_interface 21/07/2006 COMPSCI 111/111G - Lecture 03 11 21/07/2006 COMPSCI 111/111G - Lecture 03 12 Graphical User Interface (GUI)

Picture based • Windows, Icons, Mouse, Pointer • Easy to use • Good for beginners

http://en.wikipedia.org/wiki/GUI 21/07/2006 COMPSCI 111/111G - Lecture 03 13