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Lecture

lecture11.pdf

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Department
Natural Science
Course
NATS 1700
Professor
Zbigniew Stachniak
Semester
Summer

Description
Lecture 11. Software industry: its develop- ment and distribution, cultural signicance of Free Software movement Informal and unedited notes, not for distribution. (c) Z. Stachniak, 2011. Note: in cases I were unable to nd the primary source of an image or determine whether or not an image is copyrighted, I have specied the source as unknown. I will provide full information about images and/or obtain reproduction rights when such information is available to me. Introduction Computer softwarethe soul of a computeris rarely a subject of a pas- sionate discussion of new trends in information technologies. When a new smartphone is demonstrated, its amazing functionality is instinctively but unfairly linked with pressing of keys or touching of icons on the screen a physical sensation connecting our experiences more with hardware than with ... yes, with what? What is exactly happening when a smartphone is turned on? Well, several things are happening: the screen lights on, the radio is turned on, several icons appear, information appears about received e-mails, text messages, up- dates, and other information. The device begins to listen to our requests: screen touches, key presses, spoken commands. How is all of that accom- plished? When a new game is downloaded for, say the Microsofts Xbox360/Kinect console, what exactly is being downloaded? how does the downloadable stu that constitutes a game look like? and how a click on the download game now link results in such a game nding its way into an Xbox? 1 The majority of computer and communication devices operate by following instructions listed in the so-called program and stored in the devices mem- ory. This applies to computers and tablets as well as to game consoles and smartphones. So, an operating system of a smartphone (or OS), such as the Android (Google), Symbian (Nokia) iOS (Apple), BlackBerry OS (RIM), Windows Phone 7 and Windows Mobile (Microsoft) are programs, and so are Xbox games. Without programs, computers and other computing and information devices would be as useless as a book with empty pages or a game console without games. Without software your computer would be a very expensive paper- weight. The next time you send an email or play Star Wars Kinect (Lu- casArts Entertainment) take a moment to think about software engineers that made all of that possible. 2 Hardware Software Computer hardware: computers, their components and peripherals. Fig. 1. (Personal) computer hardware. Source: http://trade-oers.blogspot.com/2011/07/computer-hardware-computer-hardware.html Computer software: computer programs and associated data that deter- mine a computers operating environment and provide users with applications by commanding the hardware to perform specic tasks. Computer software is delivered to a computer for execution in the form of a sequence of instructions written in a specic so-called programming lan- guage. A computer is following these instructions in the order given in the program. The following example illustrates this idea with a little program written in the language called BASIC (see Figure 2). Can you guess what this program instructs a computer to do? 3 Fig. 2. Sample BASIC program (left) and its execution (right). Types of computer software Though there are many distinct categories of computer software (e.g. com- puter games, operating systems, spreadsheets, databases, text editors, etc.), most of them fall into two main categories: system software and application software. System software takes care of a computers functionality. When a com- puter or a smartphone is turned on, a certain kind of software is executed to perform many functions (e.g. initialization of devices such as screen, key- board, mouse, and audio card). Another kind of system software, called an operating system, enables a user to communicate with a computer and its peripherals, and to request the execution of other programs such as launch- ing a Web browser, a text editor, or a computer game. An operating system is watching a user, reacting to keyboard presses, mouse position, screen touches, and other input data. Application software is any program which is not a system software. This is a large class which includes all the apps but also other types of programs such as those used by software engineers to design and debug application pro- grams. 4
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