Building Systems & Applications Software Development, Programming, & Languages 10 Chapter

Chapter Topics 10.1 Systems Development & the Life Cycle of a Software Project 10.2 Programming: Traditionally a Five-Step Procedure 10.3 Five Generations of Programming Languages 10.4 Programming Languages Used Today 10.5 Object-Oriented & Visual Programming 10.6 Markup & Scripting Languages

10.1 Systems Development & the Life Cycle of a Software Project

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

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

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

Systems Development Life Cycle (Six Phases): Preliminary investigation Systems analysis Systems design Systems development Systems implementation Systems maintenance Information systems are frequently revised and upgraded Steps in the cycle often overlap

SDLC

SDLC 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

SDLC Phase 1

SDLC 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

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

SDLC Phase 2

Data Flow Diagram

SDLC 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

SDLC Phase 3

SDLC 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

SDLC Phase 4

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

SDLC Phase 5

SDLC Phase 6: Maintain & Update 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

SDLC Phase 6

10.2 Programming Traditionally a Five-Step Procedure

Programming is done during phase 4 of the SDLC The five steps: 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: Clarify/define the problem Design the program Code the program Test the program Document and maintain the program

Programming 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

Programming Step 1

Programming 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)

Programming Step 2

Algorithms The taxi algorithm: Go to the taxi stand. Get in a taxi. Give the driver my address. The call-me algorithm: When your plane arrives, call my cellphone. Meet me outside baggage claim. The rent-a-car algorithm: Take the shuttle to the rental car place. Rent a car. Follow the directions to get to my house. The bus algorithm: Outside baggage claim, catch bus number 70. Transfer to bus 14 on Main Street. Get off on Elm street. Walk two blocks north to my house. www.ask.com

Hierarchy Chart

Pseudocode

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

Program Flowchart & Symbols

Three Control Structures

Programming 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

Programming Step 3

Programming 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

Programming 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

Programming Step 5

Summary of Programming Steps

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

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

Machine Language Assembly Language

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

Compiler

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

Fifth Generation: Natural Languages Used mainly for artificial intelligence (AI) and neural networks Use regular human languages

Reviews of Language Generations

10.4 Programming Languages Used Today

FORTRAN COBOL 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 large computers

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

C General-purpose machine-independent compiled language developed for mid-range computers Used for portability, operating systems. And scientific use Used to write the Unix operating system Widely used for writing common software applications and is necessary for programmers to know C++ Enhanced object-oriented version of C; used for Microsoft system software and many web applications

LISP: For Artificial Intelligence Programs Third-generation language Used to control AI programs Used to write expert systems and natural language programs

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

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

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)

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

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

HTML VRML 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

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

Flash Browser add-on that uses Adobe Flash to support animation, streaming audio and video, and games on the Internet ActiveX Developed by Microsoft as an alternative to Java for creating interactive web pages 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

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 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

PHP (Personal Home Page, or PHP Hypertext Preprocessor) Allows creation of dynamic content that interacts with databases Normally found on Linux servers with MySQL databases General-purpose scripting language