CS1102 Lecture Slides - CityU CS

CS1102 Lecture Slides - CityU CS

CS1102 Lec05 - Software Computer Science Department City University of Hong Kong Objectives Describe two fundamental types of software and their relationship Describe the role and main functions of the operating system in a computer Describe the term user interface Explain the purpose of the following utilities: backup, system restore, disk defragmenter, uninstaller and screen saver Identify various operating systems Identify the categories of application software and give examples on each category Jean Wang / CS1102 - Lec05

2 Software Software - series of instructions that tell a computer what to do and how to do it Also called a program A key feature of computer programs is that they can be run or executed Software is "soft" Hardware is physically there, can be touched A software usually consists of one or more executable files and some supporting data files The extension of a file usually tells what kind of file it is, for example, .ext, .dll, .dat, .doc, .txt

Jean Wang / CS1102 - Lec05 3 Running Software HDD RAM Operating system program Word processing program Operating system interface Word processing program window

Document is saved into the hard disk Instructions and data Are removed From RAM Jean Wang / CS1102 Lec05 You make changes in the document in RAM You quit the program 1. When your computer has been booted up, operating system program is loaded into RAM 2. When you start a word processing to edit a document, both the

program and the document are loaded into RAM from the hard disk 3. When you edit the docu, the docu is only changed in RAM; When you click save button, the document is copied from RAM to hard disk 4. When you quit the word processing task, the memory for program and document is claimed back by OS for future use. 4 Types of Software System software Programs that control or maintain the operations of the computer and its devices

Application software The purpose of application software is to make users more productive and/or help with personal task E.g., word processing, game playing, e-mail, web browsing Jean Wang / CS1102 - Lec05 5 Lec05 Software - Operating System Operating System Operating system

OS acts as the master controller for all activities that take place within a computer system Hardware + OS sometimes called platform, providing the infrastructure for application software OS acts as an interface between the hardware and the application software Jean Wang / CS1102 - Lec05 7 Which following lines use OS functions ? //Scan and show the factors of x function computeResults() { var x=Number(document.getElementById("x").value);

var h=""; var count=0; var i; for (i=1;i<=x;i++) {//check through 1, 2, 3, 4, .. x for factors if (x%i==0) { h=h+i+" "; count++; } } document.getElementById("factor_list").innerHTML=h; document.getElementById("factor_count").innerHTML=count; } Jean Wang / CS1102 Lec05 8 OS Functions Process management Manages tasks that CPU works on Memory management

Memory allocation /claim back for tasks, virtual memory management File system How to store and retrieve files on disk Device management allows application software communicate with peripheral hardware component Application interface (user-interface and APIs) provides a interface for software applications to access the OS functions, such as file access, I/O, etc. Jean Wang / CS1102 - Lec05 9 Operating System Functions

Jean Wang / CS1102 - Lec05 10 Process Management Today's computers are multi-tasking which allows a single user to work on two or more programs at a time, so the processor(s) must be shared among all the programs OS ensures that each program (more precisely, a process) receives enough of the CPU time to function properly The switching between processes are so fast that it looks like several programs are running concurrently Jean Wang / CS1102 - Lec05 11 Process Management (II)

Process can have one of the following five states at a time State & Description New The process is being created. Ready The ready process is waiting to be assigned to a processor to run. Running Process that is currently being executed. Waiting The process is waiting for some event to occur, such as the completion of an I/O. Terminated The process has finished execution. Jean Wang / CS1102 - Lec05 12

Process Management (III) The operation of selecting the next process to be executed is known as scheduling. Scheduling algorithms include Head First Come First Serve (non-preemptive) Tail When the current running process finishes, the oldest process in the ready queue is selected to run next. Shortest Job First (non-preemptive) When the current running process finishes, the process in the ready queue with the shortest expected execution time is selected to run next Round Robin (preemptive) A clock interrupt is generated at periodic intervals. When the interrupt occurs, the current process is preempted, and the oldest one is selected to run next.

Nowadays many computers include multi-core processors. The operating system also supports a division of labor among all the cores. Jean Wang / CS1102 Lec05 13 Memory Management Memory management When a user initiates an application, the OS decides where to place it in memory and may allocate additional memory to the application if necessary Each program gets its own portion of memory, and OS needs to keep programs from interfering with each other's memory portion RAM Jean Wang / CS1102 - Lec05

14 Virtual Memory Memory management becomes more complex when the total memory space required exceeds the actual physical memory space Virtual Memory: borrowing some space from the hard disk functioning as additional RAM Paging technique to swap programs and data back and forth between the actual RAM and the virtual RAM Jean Wang / CS1102 - Lec05 15 Files and Directories Computer file - a named collection of data that is stored on a storage medium Files can be organized into folders (directories)

Jean Wang / CS1102 - Lec05 16 File Extension File extension is the part of file name that is separated from the main file name by a period, and it may provide a clue to the file's contents E.g., .exe, .jpg, .htm MS Windows uses a file association list to link a file extension to its corresponding application software Although a file extension is a good indicator of a files format, it does not really define the format A file header is a section of data at the beginning of a file that contains information about a file Jean Wang / CS1102 - Lec05

17 File System The smallest allocation unit, consisting of one or multiple sectors File system keeps track of the names and locations of files in Master-File-Table (one for each directory) containing: File (or directory) name Cluster IDs allocated to the file Fragmented files are stored in noncontiguous areas and may decrease performance

Defragmentation utilities help re-arrange files so that they are stored in contiguous areas Jean Wang / CS1102 - Lec05 18 Device Management The communication between OS and peripheral hardware is through the device driver Driver works as a translator translating the specialized commands of the device to commands that the OS can understand, and vice versa. It is often OS-specific (and hardwarespecific, of course), and provided by the device manufacturer Today, most devices supports Plug and Play (PnP)

Device Driver Automatically recognizes new devices as you plug them into the ports Jean Wang / CS1102 - Lec05 19 Application Interface Operating systems today are designed and developed for a specific CPU or family of CPUs Macintosh OS: Motorola CPU, IBM PowerPC CPUs, Intel CPUs Windows: Intel and AMD CPUs

Linux: Intel CPUs Unix: Sun Sparc CPUs, Intel CPUs For application programs to work the hardware, OS must contain codes that perform some common tasks, such as I/O, file access, etc. How? OS provides blocks of code for application developers to refer to or request services from Application programming interface (API) Application software can be OS dependent or developed as crossplatform applications (such as Java applications) Jean Wang / CS1102 - Lec05 20 User Interface User interface controls how users enter commands and how information is displayed on the screen Basic types include

Command line interface Keyboard input only Example includes DOS, Unix Users must remember the commands to type Menu-driven interface Graphical user interface (GUI) Jean Wang / CS1102 - Lec05 21 Elements of GUI Jean Wang / CS1102 - Lec05 1. 2.

List box Spin Control Box 3. 4. 5. 6. 7. Slide bar Drop-down List Radio Button Check Box Text Box 22 Future: 3D GUI

http://www.3dwonder.com/ http://www.sun.com/software/looking_glass/ Jean Wang / CS1102 - Lec05 23 Types of Operating Systems Types of operating systems Standalone OS (Desktop OS) OS works on a desktop or notebook computer (single-user, multi-tasking) Example includes: DOS, Windows 9x, Windows 2000, Windows XP, Windows Vista, Windows 7, Mac OS, OS/2, Unix, Linux Network OS OS runs on servers (multi-user, multi-tasking), providing communication and routing services which coordinates communication between the other computers

Example includes: Novell Netware, Windows NT server, Windows 2000 server, Windows 2003 server, Windows 2008 server, Unix, Linux, Sun Solaris, MVS and VM for IBM mainframes Embedded OS OS runs on mobile devices such as PDAs and cell phones (single user, multi-tasking) Example includes: Windows CE, Palm OS, Windows Phone 7, iPhone OS, BlackBerry OS, Google Android, Embedded Linux, Symbian OS Jean Wang / CS1102 - Lec05 24 Mac OS Mac OS Runs on Apple computers Popular for its photo-quality icons and easy-to-use menus Latest version is Mac OS X Jean Wang / CS1102 - Lec05

25 Unix and Linux The Unix OS was developed in 1969 at AT&T's Bell labs Gained a good reputation for its robustness and reliability in multi-user environments Popular choice for servers, mainframes and supercomputers The Linux OS (version of UNIX) was developed by a young Finnish student named Linus Torvalds in 1991 Encouraging programmers to develop utilities, enhancement and share with others

Open source No propriety Google Chrome OS based on Linux Jean Wang / CS1102 - Lec05 26 Unix and Linux Unix/Linux users can choose from several graphical interfaces Jean Wang / CS1102 - Lec05 27 Embedded Operating Systems An embedded operating system resides on a ROM

chip on a mobile device or consumer electronic device Jean Wang / CS1102 - Lec05 28 Lec05 System Software Utilities Utility Programs to Enhancing an OS A utility program is a kind of system software that provides extensions of operating system capabilities. Utility programs often performs tasks related with system maintenance, for example Backup utility Copies selected files or entire hard disk onto another disk or tape (often compressed to save storage space)

System restore utility Rewinds your PC back to an early time (called a restore point) Disk defragmenter Re-organizes files and unused space on hard disk so programs run faster Security utilities Detects and protects a computer from malicious software or unauthorized intrusions Other utilities include software uninstaller, screen saver, performance 30 Jean Wang / CS1102 - Lec05monitor, troubleshooting, personal firewall, and Lec05

Software Application Software Application Software Application Software Differing from system software, applications help you personally to accomplish some specific tasks Jean Wang / CS1102 - Lec05 32 Business Software To assist people with business activities Word processing - allows user to create and manipulate text and graphics Common features in word

processing software Spelling check Grammar check AutoCorrect Search and replace Speech input Thesaurus Tracking changes Mail merge

Jean Wang / CS1102 - Lec05 33 Business Software - Spreadsheet A spreadsheet uses rows and columns of numbers to Organize data Perform calculations by built-in or user-defined formulas Turn the numbers into graphic reports and charts Jean Wang / CS1102 - Lec05 34 Spreadsheet Software (cont'd) In spreadsheet, a formula tells the computer how

to use the contents of cells in calculations E.g., =D4 - D5 + (D8 * 1.1) A formula can contain Cell references Mathematical operators Functions (e.g., SUM, AVG, MIN, MAX, IF .) Charting depicts data in a spreadsheet in a graphical form Microsoft Office also provides macro coding feature allowing users to write small programs to automate repetitive tasks in Office applications MS macros are in VBA code (Visual Basic Application) Jean Wang / CS1102 - Lec05 35 Business Software - Database A database is simply a collection of data organized in

a manner that allows access, retrieval, and use of that data Data software allows you to To enter, find, organize, update and retrieve information stored in a database Database software stores data as a collection of records of data fields hold data composed A record holds for that a single entity such as a person, place, thing or event A field holds a specific piece of information within a record Records are arranged in a grid of rows

and columns (table) Jean Wang / CS1102 - Lec05 36 Database Software (cont'd) A query language such as SQL (Structured Query Language) provides a set of commands for locating and manipulating data Example: SELECT Name FROM Student WHERE Grade = 'F' Popular database systems MS Access, MySQL, MS SQL

server, Oracle database Jean Wang / CS1102 - Lec05 37 Other Business Software Presentation graphics software Used to create visual aids for presentations (or slide shows) Personal information manager (PIM) Includes a calendar, address book, a task-to-do list Most PDAs and many smart phones include PIM functionality, and can be synchronized with desktop computers Project management software Allows you to plan, schedule, track, and analyze the

events, resources, and costs of a project Accounting software Helps companies record and report their financial transactions Jean Wang / CS1102 - Lec05 38 Graphics and Multimedia Software Popular graphics and multimedia software products Jean Wang / CS1102 - Lec05 39 Graphics and Multimedia Software

Computer-aided design (CAD) software Allows you to create engineering, architectural, and scientific designs Desktop publishing software Enables you to design and produce sophisticated documents that contain text, graphics, and many colors Jean Wang / CS1102 - Lec05 40 Graphics and Multimedia Software Paint/Image editing

software Used to create and modify graphical images Audio editing software Allows you to make your own digital voice and music recordings Audio editing software CD ripper software Audio encoding software Computer-aided music software MIDI sequencing software

Jean Wang / CS1102 - Lec05 41 Graphics and Multimedia Software Video /Audio editing software Video editing software allows you to modify a segment of a video, called a clip Audio editing software allows you to Transferring video footage from a camcorder to a computer Clipping out unwanted footage Assembling video segments Adding special visual effects

Adding a sound track Jean Wang / CS1102 - Lec05 42 Graphics and Multimedia Software Multimedia authoring software Allows you to combine text, graphics, audio, video, and animation into an interactive presentation Web page authoring software Allows users of all skill levels to create Web pages

Jean Wang / CS1102 - Lec05 43 Software for Home, Personal, and Educational Use Personal finance software Tax preparation software Travel and mapping software Home design software Educational software Entertainment software

Media players Computer games Jean Wang / CS1102 - Lec05 44 Application Software for Communications Communication software facilitates communication and data sharing between people Email Web browser Web application is a software program which the user accesses over a network with a web browser

Instant messaging RSS Aggregator Blogging Video conferencing FTP VoIP Peer to peer file sharing Jean Wang / CS1102 - Lec05 45 Desktop Applications vs. Web Apps vs. Mobile Apps

Desktop apps Application software running on desktop/notebook computers Could be developed separately for each operating system or developed as cross-platform applications Need installation Mobile native apps Applications specially designed to run on a

devices OS, and typically needs to be adapted for different devices Need installation Web apps (desktop or mobile) Good ? Bad? Users? Developers? Jean Wang / CS1102 - Lec05 Front-end clients specifically designed for running in browsers Need Internet connection to back-end servers NO need installation 46

Software License Commercial software is copyrighted so it cannot be legally duplicated for distribution to others A copyright is a form of legal protection that grants the author of an original work exclusive rights to copy, distribute, sell and modify that work Software License A legal contract that defines the ways in which you may use a computer program Single-user license, multiple-user license, site license Where is the license exactly EULA (End-User License Agreement): Agree or Not Agree Software piracy is used to describe the unauthorized copying and selling of software Jean Wang / CS1102 - Lec05

47 Software License Different levels of permission for software use, copying and distribution Commercial software You only buy the right to use it Shareware Distributed free for trial period; after trial period, you need to pay Freeware Copyrighted software at no cost You can make copies, distribute it but cannot change it or sell it Open source software Copyrighted software distributed together with its source code

You can use, modify, and redistribute it Public-domain software No copyright restrictions You can freely copy, distribute, and even sell it; but you are not 48 Jean Wang / CS1102 - Lec05 allowed to apply for a copyright on it Lesson Summary A computer's software is like the chain of command in an army Application software tells the operating systems how to do The operating system tells the device drivers

The device drivers tell the hardware The hardware actually does the work Software copyright is a form of legal protection that grants the software author an exclusive right to copy, distribute, sell, and modify that software Software license is a legal contract that defines the ways in which you may use a software Commercial, shareware, freeware, open source, and public domain software Jean Wang / CS1102 - Lec05 49 Lesson Summary (continued) OS functions include Interacting with computer hardware to manage a computer's resources, which include the CPU, main memory and other peripheral devices

Providing the user interface Providing the interface for application software Application software helps user accomplish some specific tasks, and it includes four basic kinds Business Graphic and multimedia Education, home and personal use Communication Jean Wang / CS1102 - Lec05 50

Reference [1] Wikipedia - Operating System http://en.wikipedia.org/wiki/Operating_system [2] HowStuffWorks.com - Operating System http://computer.howstuffworks.com/operating-system.htm [3] CPU Process Switching Animation http://courses.cs.vt.edu/~csonline/OS/Lessons/Processes/index.html [4] Wikipedia - History of Microsoft Windows http://en.wikipedia.org/wiki/History_of_Microsoft_Windows [5] Wikipedia - Linux http://en.wikipedia.org/wiki/Linux [6] Wikipedia - Spreadsheet http://en.wikipedia.org/wiki/Spreadsheet Jean Wang / CS1102 - Lec05

51 For you to explore after class Lec05-Q1: explain why Windows can support PnP, i.e., the addition of a new device without requiring reconfiguration or manual installation of device drivers? Lec05-Q2: depending on the file system and disk volume, a cluster ranges in size from one sector to several sectors. State how using large-sized clusters would affect disk utilization ratio and the system performance, comparing to using small-sized clusters.

Lec05-Q3: make a list of 6 file extensions you find in a computer that you use most often. Explain each of the extensions are for what type of files E.g., .exe - for executable files Jean Wang / CS1102 - Lec05 52

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