UNIT 2 COMPUTER SOFTWARE

Transcription

1 UNIT 2 COMPUTER SOFTWARE Computer Software -Types of Software - Software Development Steps - Internet Evolution - Basic Internet Terminology - Getting connected to Internet Applications. 2.0 Computer Software Hardware : Hardware is a comprehensive term for all of the physical components of a computer, as distinguished from the data it contains or operates on it. It includes all mechanical, electronic and magnetic devices such as monitor, printer, electronic circuit, floppy and hard disk. Software Software refers to the set of computer programs, which are used in applications and operating systems. It is the collection of datas and instructions, which iperforms particular task.it increases the software capability of the computer. The process of software development is called programming. 2.1 Software Types Computer software is normally classified into two broad categories. Application Software System software

2 System Software: An instruction is a set of programs that has to be fed to the computer for operation of computer system as a whole. When you switch on the computer the programs written in ROM is executed which activates different units of your computer and makes it ready for you to work on it. This set of program can be called system software. Therefore system software may be defined as a set of one or more programs designed to control the operation of computer system. System software are general programs designed for performing tasks such as controlling all operations required to move data into and out of the computer. It communicates with printers, card reader, disk; tapes etc. monitor the use of various hardware like memory, CPU etc. Also system software are essential for the development of applications software. System Software allows application packages to be run on the computer with less time and effort. A) Operating system: - First layer of software loaded into the computer memory when it starts up. - Organizes and controls the hardware.

3 Basic Functions: Process Management: Handles the creation, deletion, suspension, resumption and synchronization of processes. Memory management: Handles allocation and de-allocation of memory space as required by various programs. File Management: Responsible for creation, deletion and other basic operations on files and directories. Device management: Manages all devices of the computer system. Security management: Protects system resources and information against destruction and other unauthorized use. User Interface: Provides interface between user and the hardware. B) Device drivers: A device driver, or software driver, is a computer program allowing higher level Computer programs to interact with a device. A driver typically communicates with the device through the computer bus or communications subsystem to which the hardware is connected. When a calling program invokes a routine in the driver, the driver issues

4 commands to the device. Once the device sends data back to the driver, the driver may invoke routines in the original calling program. Drivers are hardware-dependent and operating-system-specific. They usually provide the interrupt handling required for any necessary asynchronous time-dependent hardware interface. C)Language translators. (i) Compiler: A compiler is a computer program that translates a computer program written in one computer language (called the source language) into an equivalent program written in another computer language (called the output, object, or target language). Most compilers translate source code written in a high level language to object code or machine language that may be directly executed by a computer or a virtual machine. (ii) Interpreter A high-level programming language translator that translates and runs the program at the same time. It translates one program statement into machine language, executes it, and then proceeds to the next statement. This differs from regular executable programs that are presented to the computer as binary-coded instructions. Interpreted programs remain In the source language the programmer wrote in, which is human readable text. Slower, But Easier to Test Interpreted programs run slower than their compiler counterparts. Whereas the compiler translates the entire program before it is run, interpreters translate a line at a time while the program is being run. However, it is very convenient to write an interpreted program, since a single line of code can be tested interactively.

5 (iii)assembler Software that translates assembly language into machine language. Contrast with Compiler, which is used to translate a high-level language, such as COBOL or C, into assembly language first and then into machine language Application software A program or group of programs designed for end users. A) Word processor Using a computer to create, edit, and print documents. Of all computer applications, word processing is the most common. To perform word processing, you need a computer, a special program called a word processor, and a printer. A word processor enables you to create a

6 document, store it electronically on a disk, display it on a screen, modify it by entering commands and characters from the keyboard, and print it on a printer. The great advantage of word processing over using a typewriter is that you can make changes without retyping the entire document. If you make a typing mistake, you simply back up the cursor and correct your mistake. If you want to delete a paragraph, you simply remove it, without leaving a trace. It is equally easy to insert a word, sentence, or paragraph in the middle of a document. Word processors also make it easy to move sections of text from one place to another within a document, or between documents. When you have made all the changes you want, you can send the file to a printer to get a hardcopy. Word processors vary considerably, but all word processors support the following basic features: Insert text: Allows you to insert text anywhere in the document. Delete text: Allows you to erase characters, words, lines, or pages as easily as you can cross them out on paper. Cut and Paste : Allows you to remove (cut) a section of text from one place in a document and insert (paste) it somewhere else. Copy : Allows you to duplicate a section of text. Page size and margins : Allows you to define various page sizes and margins, and the word processor will automatically readjust the text so that it fits. Search and Replace : Allows you to direct the word processor to search for a particular word or phrase. You can also direct the word processor to replace one group of characters with another everywhere that the first group appears. Word wrap : The word processor automatically moves to the next line when you have filled one line with text, and it will readjust text if you change the margins. Print: Allows you to send a document to a printer to get hardcopy.

7 Word processors that support only these features (and maybe a few others) are called text editors. Most word processors, however, support additional features that enable you to manipulate and format documents in more sophisticated ways. These more advanced word processors are sometimes called full-featured word processors. B) Spreadsheet A table of values arranged in rows and columns. Each value can have a predefined relationship to the other values. If you change one value, therefore, you may need to change other values as well. Spreadsheet applications (sometimes referred to simply as spreadsheets) are computer programs that let you create and manipulate spreadsheets electronically. In a spreadsheet application, each value sits in a cell. You can define what type of data is in each cell and how different cells depend on one another. The relationships between cells are called formulas, and the names of the cells are called labels. C) Database management system A collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMSs, ranging from small systems that run on personal computers to huge systems that run on mainframes. The following are examples of database applications: computerized library systems automated teller machines flight reservation systems computerized parts inventory systems D) Presentation graphics

8 A type of business software that enables users to create highly stylized images for slide shows and reports. The software includes functions for creating various types of charts and graphs and for inserting text in a variety of fonts. Most systems enable you to import data from a spreadsheet application to create the charts and graphs. E) Desktop publishing Using a personal computer or workstation, we can produce high-quality printed documents. A desktop publishing system allows you to use different typefaces, specify various margins and justifications, and embed illustrations and graphs directly into the text. The most powerful desktop publishing systems enable you to create illustrations; while less powerful systems let you insert illustrations created by other programs. 2.2 Software Development Steps: Before starting the process of writing a program, the programmer has to determine the problem that needs to be solved. There are different approaches to problem solving. Most require breaking the problem into a series of smaller steps, independent of the programming language. One common technique is to use the Software development Life Cycle, with the number of steps that may vary according to the person who has formalized the development. Software Development Life Cycle of a program includes the following phases: i) Analyse : Define the Problem The problem is analyzed precisely completely. Task Analysis After analyzing the problem, the developer needs to develop various solutions to solve the given problem. From these solutions, the optimum solution (by experimenting with all the solutions) is

9 chosen, which economically. can solve the problem comfortably and ii) Designing Phase: After selecting the appropriate solution, algorithm is developed to depict the basic logic of the selected solution. An algorithm depicts the solution in logical steps. Further, algorithm is represented by flowcharts and pseudocodes. These tools make program logic clear and they eventually help in coding. This phase is also known as design phase. iii) Testing Phase: We are testing the Algorithm for Accuracy. Before converting the algorithms into actual code, it should be checked for accuracy. The main purpose of checking algorithm is to identify major logical errors at an early stage, because logical errors are often difficult to detect and correct at later stages. The testing also ensures that the algorithm is a true one and it should work for both normal as well as unusual data. iv) Coding: After meeting all the design consideration, the actual coding of the program takes place in the chosen programming language. Depending upon application domain and available resources, a program can be written by using computer languages of different levels such as machine, assembly or high level languages. v) Debug the program: It is common for the initial program code to contain errors. A program compiler and programmer designed test data machine tests the code for syntax errors. The results obtained are compared with results calculated

10 manually from this test data. Depending upon the complexity of the program, several rounds of testing may be required. vi) Documentation and Implementation: Once the program is free from all the errors, it is the duty of the program developers to ensure that the program is supported by suitable documentation. After documentation, the program is installed on the end user s machine. 2.4 EVOLUTION OF INTERNET 1960 origin of internet-us Department of Defense wanted to create a computer network that could continue to function even in the disaster. ARPANET Advance Research Projects Agency Network. It is used in the US Scientific and academic researchers-fore runner of today s internet s ARPANET helped in the developed new protocol known as TCP / IP for transmitting data b/w n/w. This is core of internet s NSF (National Science Foundation) used ARPANET to link its 5 regional super networks, so users share their work. So, NSF is Creating NSFNET. In 1980 s USENET newsgroups & E mail. Indices such as Archie & WAIS(wide area information server), were created to track of i/f in d internet. To give user an easy-to-use interface to work, GOPHER simple menu driven system for accessing files were created. In 1991 CERN released world wide web. This team developed the protocol based on hypertext that makes it possible to connect the content on the web with hyperlinks. In June 1993, there were only 130 websites, but now there are millions.

11 2.5 BASIC INTERNET TERMS a) Web Browser A web browser can also be defined as an application software or program designed to enable users to access, retrieve and view documents and other resources on the Internet. Non-graphical a user interface for computers which allows you to read plain text, not pictures, sound, or video, on the Internet. An example is lynx.( Graphical a user interface for computers which enables people to see color, graphics, and hear sound and see video, available on Internet sites. Examples are Firefox and Internet Explorer

12 b) Domain Name A method of identifying computer addresses. Your address has a domain address. Examples: Commercial and for profit organizations..edu - Colleges and universities

13 .gov - Federal government agencies..mil - US military sites..net - Internet infrastructure and service providers..org - Miscellaneous and non profit organizations. c) FTP File Transfer Protocol is a standard network protocol used to transfer files from one host to another over a TCP-based network, such as the Internet. d) HTTP- The hypertext transfer protocol It enables html documents to be read on the Internet.

14 e) Uniform Resource Locator (URL) f) Each web page has a unique address, called a Uniform Resource Locator (URL) that identifies its location on the Internet. Web browsers utilize the URL to retrieve a file from the computer on which it resides. URL consists of six parts: protocol, www, server (or domain), domain type, path and file name. ftp:// Example : Protocol World Wide Web : http : www

15 Domain Name Path File Name : xyz : tutor / start / : main.html g) Web page World Wide Web consists of files, called pages or web pages, which contain information and links to resources throughout the Internet. A web page is an electronic document written in a computer language called HTML. h) Website

16 A website is a related web page, published by an organization or individual. Web site contains a home page along with other additional web pages. Each website is owned and updated by an individual, company or organization. i) Home page A home page is the starting point or a doorway to the website. Like the table of contents of a book, the home page usually provides an overview of what could be found at the website

17 j) Hypertext Hypertext refers to the text or image that connects to other documents. These texts or images are known as hypertext link, hyperlink, hotlink or simply links. A hyperlink is used to jump to another part of the same page or to load different web pages. Hypertext is a method of instant cross referencing. It is used for organizing information and to link related documents together using words and graphics (also known as image maps.)

18 k) Blog A blog is information that is instantly published to a Web site. Blog scripting allows someone to automatically post information to a Web site. The information first goes to a blogger Web site. Then the information is automatically inserted into a template tailored for your Web site.

19 l) Bookmark It is a way of storing your favorite sites on the Internet. Browsers like Netscape or Internet Explorer let you to categorize your bookmarks into folders.

20 m)internet Service Provider (ISP) An ISP is a company that provides access to the internet to individuals or companies. For a monthly fee, the ISP provides the user software package, username, password, and access phone number(s). Equipped with a modem, the user can then log on to the Internet and browse the web.

21 n) Web Server A server is a computer equipped with server software, which provides a specific kind of service to client software running on other computers The term can refer to a particular piece of software, for example, a web server, or to the machine on which the software is running. A web server is a computer that answers requests from user s computers. It serves images and static content, such as web pages, to fill the client s requests. Web servers can run on any hardware platform and operating system and store documents in HTML. o) Cookie Information (in this case URLs, Web addresses) created by a Web server are stored on a user s computer. This information lets Web sites the user visits to keep of a user s browsing patterns and preferences.

22 People can set up their browsers to accept or not accept cookies. p) Download and Upload Download means download the file or image from remote system to another system. Upload means file or image one system to remote system. q) Online and Offline Online means Connected to World Wide Web via Internet. Offline means Opposite of the Online 2.6 GETTING CONNECTED TO INTERNET Basic requirements for getting online are: 1. A TCP / IP enabled computer with a web browser. 2. An account with an ISP. 3. A telephone line plugged to suitable socket 4. A modem to connect the computer to the telephone line. Basic requirements for Computer: 1. Pentium III / Pentium IV MB / 256 MB RAM * 480 resolution and minimum of 256 colors. 4. Atleast 200MB of Hard Disk. 5. Sound Card. Basic requirement for MODEM: 1. Modem range 28 kbps to 56 kbps.

23 2. Modem type is internal or external TYPES OF INTERNET CONNECTION i) Dial Up Internet Connection This type connection is used in the Home computers Access method of this connection is connected to a telephone line. The user needs to specify a username, a password, and telephone number. ii) ISDN (Integrated Services Digital Network) It is more common in business and commercial use. High speed alternative to regular analog phone modems. ISDN involves the digitization of telephone network so that voice, graphics, text, and other data can be provided to users from a single terminal over existing telephone wiring.

24 Digital connection have fewer errors in transmission, which means speed of down loading graphics, web pages, sound, and so on, is increased to four times faster than with dial up modems. iii)cable Modem A cable modem connects the user to the Internet through a cable television line. Cable modem will typically have two connections, one to the television outlet and the other to the computer. Cable modems not only provide a faster Internet access (10 to 100) times as fast as the dial up modem), but they also give added interactivity to the television. iv) Leased Line

25 This facility provides reliable, high speed Internet access ranging from 2.4 kbps to 45 Mbps. This is a fixes monthly charge. Leased Line facility can be provided via fiber optic or copper lines. It provides a consistent amount of bandwidth and is an excellent way to provide data, voice and video links between sites. v) DSL (Digital Subscriber Line) It provided through the existing phone line but it works differently than regular analog modem dial up access. DSL Operates over normal telephone lines and it can be used simultaneously with the telephone.

26 DSL can increase the connection speed by as much as ten fold from a standard dial up modem. Vi) Broadband This type of access is good for remote location, where ISDN, cable or DSL are not available. Example Broadband connection is Satellite Internet connection. But very expensive.