uit9 ppt ch10_au_rev
TRANSCRIPT
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Systems Analysis & Programming
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10.1 Systems Development
Purpose of a System A System is a collection of related components that
interact to perform a task in order to accomplish a goal A computer-based system consists of hardware,
software, people, procedures, and data, as well as communications setups
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10.1 Systems Development
How It Starts, Who’s Involved Users: The new system must ALWAYS be developed in
consultation with the people who will be using the completed system
Management: Managers within an organization should be consulted about the system, because they control the budget and resources
Technical staff: The Information Systems or IT staff must be involved, because they will have to execute the project or work with the people who do
Systems Analyst: Information specialist who performs systems analysis, design, and implementation
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10.1 Systems Development
Six Phases of Systems Analysis and Design Systems analysis and design is a six-phase problem-
solving procedure for examining an information systems and improving it
The systems development life cycle (SDLC) is the particular step-by-step process followed during systems analysis and design
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10.1 Systems Development
Systems Development Life Cycle (Six Phases):1. Preliminary investigation
2. Systems analysis
3. Systems design
4. Systems development
5. Systems implementation
6. Systems maintenance Information systems are frequently revised and
upgraded Steps in the cycle often overlap
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10.1 Systems Development
Phase 1: Conduct a Preliminary Investigation Conduct a preliminary analysis Propose alternative solutions
Interview people within the organization Study what competitors are doing Decide to leave the system as is, improve it, or develop a
new system Describe costs and benefits Submit a preliminary plan with recommendations
This should be a written report Get management approvals for next phase
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10.1 Systems Development
Phase 2: Analyze the System Gather data
Interview employees and managers Develop, distribute, analyze questionnaires Review current written documents Observe people and processes at work
Analyze the data Use modeling tools, such as CASE tools Create a data flow diagram to show how data flows through
the system
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10.1 Systems Development
Phase 2: Analyze the System (continued) Write a report
Document how the current system works Document problems with the current system Describe the requirements for the new system Recommend what to do next Get management approval to proceed
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10.1 Systems Development
Phase 3: Design the System Do a preliminary design
Often involves prototyping and continued use of CASE tools Do a detail design, showing:
Output requirements Input requirements Storage requirements Processing requirements System controls Backup
Write a report and get approval for next phase© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
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10.1 Systems Development
Phase 4: Develop the System Develop or acquire the software
Make-or-buy decision If creating own system, programming (coding must be
done) Acquire or upgrade the hardware Test the system
Unit testing: performance of system’s individual parts tested System testing: parts are linked and tested to see if they
work together properly; real data may be used
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10.1 Systems Development
Phase 5: Implement the System Choose a strategy to convert to the new system
Direct implementation: quit the old and start using the new Parallel implementation: use both the old and the new side
by side, until the new system has been proved reliable Phased implementation: phase in parts of new in gradually
as parts of old are phased out Pilot implementation: have the new system tried out by a
few users Train the users
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10.1 Systems Development
Phase 6: Maintain the System Perform system audits and periodic evaluations Make changes to the system based on new conditions Finalize documentation
Note that documentation should have been continuously maintained during the entire SDLC
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10.2 Programming: A Five-Step Procedure
A program is a list of instructions that the computer must follow to process data into information
Programming is done during phase 4 of the SDLC The five steps:
1. Clarify/define the problem
2. Design the program
3. Code the program
4. Test the program
5. Document and maintain the program
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10.2 Programming: A Five-Step Procedure
Step 1: Clarify the Programming Needs Clarify objectives & users Clarify desired outputs Clarify desired inputs Clarify the desired processing Double-check the feasibility of implementing the program Document the analysis
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10.2 Programming: A Five-Step Procedure
Step 2: Design the Program Create an algorithm, or set of clear steps, to solve the
problem Use structured programming approach
Determine program logic using top-down approach and modules, using a hierarchy chart (graphic form) and pseudocode (narrative form)
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10.2 Programming: A Five-Step Procedure
Pseudocode
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10.2 Programming: A Five-Step Procedure
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10.2 Programming: A Five-Step Procedure
Step 2: Design the Program (continued) Structured programming
Use control structures: Sequence: one statement follows another in logical order Selection: IF-THEN-ELSE Iteration (loop): DO UNTIL / DO WHILE
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10.2 Programming: A Five-Step Procedure
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10.2 Programming: A Five-Step Procedure
Step 3: Code the Program Translate the logic requirement from flowcharts and
pseudocode into a programming language Select a programming language--set of rules that tells the
computer what operations to do Each programming language has a syntax, or set of
grammatical rules to follow to write valid expressions Syntax rules must be followed or there will be syntax errors Computers don’t understand what you want, only what you
type in
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10.2 Programming: A Five-Step Procedure
Step 4: Test the Program Desk checking is reading through, or checking, the
program for syntax errors and logic errors Debugging is the process of detecting, locating, and
removing all syntax errors and logic errors in a computer program
Beta testing is the process of testing the program using real data One phase of testing uses correct data Once the program works, the next phase of testing uses
invalid data and untrained users to root out hidden errors
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10.2 Programming: A Five-Step Procedure
Step 5: Document and Maintain the Program Documentation is written descriptions of what a program
is and how to fix it; should be done through all 5 steps User documentation – for the people who will use the
program (e.g., user manual – hardcopy or CD, and online) Operator documentation – for the computer operators, so
they know what to do if the program or hardware malfunctions
Programmer documentation – for the next programmer who must modify and maintain what has been written
Maintain the program – keep everything in working condition
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10.3 Five Generations of Programming Languages
First Generation: Machine Language The basic language of the computer – all 0s and 1s Each CPU model has its own machine language, thus
machine language is machine dependent Not convenient for people to read and use Evolution of languages started in 1945
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10.3 Five Generations of Programming Languages
Second Generation: Assembly Language Low-level mnemonic version of machine language; uses
abbreviations and simple words Faster to program in than machine language Is also machine dependent Assembler program needed to translate assembly
language into machine language
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10.3 Five Generations of Programming Languages
Third Generation: High-level Languages (Procedural Languages) These languages resemble human language (e.g.,
English) and are portable (not machine dependent) Examples are FORTRAN, COBOL, BASIC, Pascal, C The programmer writes the source code, then uses a
translator program to interpret or compile the code into machine language (object code) Interpreter translates and executes immediately Compiler translates and saves the code as an entire unit to
be executed later
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10.3 Five Generations of Programming Languages
Fourth Generation: Very-High-Level or Problem-Oriented Languages Easier to program in than third-generation languages Three types:
Report generators (RPGIII) Query languages (SQL) Application generators (NOMAD, FOCUS)—used to create
parts for other programs
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10.3 Five Generations of Programming Languages
Fifth Generation: Natural Languages Programming languages that use human language to
give people a more natural connection with computers Part of the field of artificial intelligence (AI; Chapter 8)
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10.4 Programming Languages Used Today
FORTAN The language of mathematics The first high-level language written A machine-independent procedural language
COBOL The most-frequently used language for business legacy
applications on mainframe computers A machine-independent procedural language
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10.4 Programming Languages Used Today
BASIC Designed to be an easy language to use and learn
programming with Usually run from an interpreter, but can be compiled Procedural language Supplanted by Microsoft’s Visual Basic for
commercial/business use Pascal
Designed to be a language to teach programming Structured, compiled language Not used in business or commercial companies
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10.4 Programming Languages Used Today
C General-purpose machine-independent compiled
language developed for mid-range computers Used to write the Unix operating system Widely used for writing common software applications
and is necessary for programmers to know Doesn’t handle math as well as FORTRAN
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10.4 Programming Languages Used Today
LISP: For Artificial Intelligence Programs Third-generation language Used to control AI programs Used to write expert systems and natural language
programs
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10.5 Object-Oriented & Visual Programming
In object-oriented programming (OOP), data and processing instructions are combined into a self-sufficient object that can be reused Object
Self-contained module consisting of reusable code Message
The instruction received by the object indicating it is time to perform an action
Method The processing instructions within the object to perform the
specified action
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10.5 Object-Oriented & Visual Programming
Three basic concepts of OOP Encapsulation
One object contains (encapsulates) both data and relevant processing instructions
Inheritance One object can be used as the foundation for other objects Objects can be arranged in hierarchies – classes and
subclasses Objects can inherit actions and attributes from one another
Polymorphism Allows a single definition to be used with different data types
and different functions Means a message produces different results depending on the
object it is sent to© 2011 The McGraw-Hill Companies, Inc. All rights reserved.
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10.5 Object-Oriented & Visual Programming
Examples of OOP languages C++
Object-oriented language that was developed after C Often used to write computer games and CPU- and
graphics-intensive applications Java
Developed at Sun Microsystems in early 1990s Derivative of C++ with simpler memory management and
syntax Used to develop Java applets to be downloaded into web
browsers to make websites interactive and more attractive (e.g., with animations)
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10.5 Object-Oriented & Visual Programming
Visual programming is a method of creating programs in which the programmer makes connections by clicking on objects, diagrams, and icons and by interacting with flowcharts
Using a mouse, the programmer drags and drops objects on screen This makes it fast and easy to build prototype user interfaces
and get end-user approval before doing a lot of programming
Visual BASIC is an example of visual programming
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10.6 Markup & Scripting Languages
A markup language is a kind of coding (“tags”) inserted into text that embeds details about the structure and appearance of the text HTML is a markup language (internet use)
Has codes for indicating layout and styling (such as boldface, italics, paragraphs, insertion of graphics, etc.)
SGML: improved markup language Specifies a syntax for including the markup in documents Allows users to create and use any markup they wish
Script: short list of self-executing commands embedded in a web page that perform a specified function or routine
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10.6 Markup & Scripting Languages
HTML Hypertext markup language Used to create 2-D web pages Also lets you insert hypertext links in web pages
VRML Virtual Reality Modeling (Markup) Language is used to
create 3-D web pages, including interactive animation Requires special VRML browser to view VRML pages Used by web designers, along with HTML
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10.6 Markup & Scripting Languages
XML eXtensible Markup Language is a metalanguage written
in SGML that allows one to facilitate easy document interchange on the internet
XML lets you create your own tags (“extensible”) XML statements define data content
JavaScript Not the same language as Java An object-oriented scripting language that adds
interactive functions to HTML web pages
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10.6 Markup & Scripting Languages
ActiveX Developed by Microsoft as an alternative to Java for creating
interactive web pages A set of controls or components that enable programs or
content of almost any type to be embedded in a web page; comprises reusable components that can be plugged into other applications
ActiveX controls are written in C, C++, Visual BASIC, and Java Often used by crackers to propagate viruses and/or Trojans;
before you allow an ActiveX component to download from your browser to your computer, make sure you trust that website
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10.6 Markup & Scripting Languages
Perl A general-purpose programming language developed for
text manipulation. Used for web development, network programming,
system administration, GUI development, other tasks Widely used for web server programs to perform
automatic tasks such as updating user accounts and newsgroup postings
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10.6 Markup & Scripting Languages
CGI (Common Gateway Interface) Standard protocol for interfacing external application
software with a web server Manages the exchange of information and makes web
pages more interactive TCL (Tool Command Language)
Created for the Unix platform Interpreted script language Comparable to JavaScript and Visual BASIC
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10.6 Markup & Scripting Languages
Ruby Basic and completely object-oriented scripting language Open-source language Can be compiled and run on most operating systems
PHP (Personal Home Page, or PHP Hypertext Preprocessor) and R Allows creation of dynamic content that interacts with
databases Normally found on Linux servers with MySQL databases General-purpose scripting language R used in data mining
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