Encyclopedia of Computer Science and Technology

CASE 73Meyer, Eric A. CSS: The Definitive Guide. 3rd ed. Sebastapol, Calif.:O’Reilly, 2007.“Zen Garden: The Beauty of CSS Design.” Available online. URL:http://www.csszengarden.com. Accessed May 19, 2007.CASE (computer-aided software engineering)During the late 1950s and 1960s, software rapidly grew morecomplex—especially operating system software and largebusiness applications. With the typical program consistingof many components being developed by different programmers,it became difficult both to see the “big picture”and to maintain consistent procedures for transferring datafrom one program module to another. As computer scientistsworked to develop sounder principles (see structuredprogramming) it also occurred to them that the power ofthe computer to automate procedures could be used to createtools for facilitating program design and managing theresulting complexity. CASE, or computer-aided softwareengineering, is a catchall phrase that covers a variety of suchtools involved with all phases of development.Design ToolsThe earliest design tool was the flowchart, often drawnwith the aid of a template that could be used to trace thesymbols on paper (see flowchart). With its symbols forthe flow of execution through branching and looping, theflowchart provides a good tool for visualizing how a programis intended to work. However large and complex programsoften result in a sea of flowcharts that are hard torelate to one another and to the program as a whole. Startingin the 1960s, the creation of programs for manipulatingflow symbols made it easier both to design flowcharts andto visualize them in varying levels of detail.Another early tool for program design is pseudocode, alanguage that is at a higher level of abstraction than the targetprogramming language, but that can be refined by addingdetails until the actual program source code has beenspecified (see pseudocode). This is analogous to a writeroutlining the main topics of an essay and then refiningthem into subtopics and supporting details. Attempts weremade to create a well-defined pseudocode that could beautomatically parsed and transformed into compilable languagestatements, but they met with only limited success.During the 1980s and 1990s, the graphics capabilitiesof desktop computers made it attractive to use a visualrather than linguistic approach to program design. Symbols(sometimes called “widgets”) represent program functionssuch as reading data from a file or creating various kindsof charts. A program can be designed by connecting thewidgets with “pipes” representing data flow and by settingvarious characteristics or properties.CASE principles can also be seen in mainstream programmingenvironments such as Microsoft’s Visual Basicand Visual C++, Borland’s Delphi and Turbo C++, and others(see also programming environment). The designapproach begins with setting up forms and placing objects(controls) that represent both user interface items (such asmenus, lists, and text boxes) and internal processing (suchas databases and Web browsers). However these environmentsdo not in themselves provide the ability of full CASEtools to manage complex projects with many components.Analysis ToolsOnce a program has been designed and implementation isunder way, CASE tools can help the programmers maintainconsistency across their various modules. One such tool(now rather venerable) is the data dictionary, which is adatabase whose records contain information about the definitionof data items and a list of program components thatuse each item (see data dictionary). When the definitionof a data item is changed, the data dictionary can providea list of affected components. Database technology is alsoapplied to software design in the creation of a database ofobjects within a particular program, which can be used toprovide more extensive information during debugging.Integration and TrendsA typical CASE environment integrates a variety of toolsto facilitate the flow of software development. This processmay begin with design using visual flowcharting,Many tools are used today to aid the complex endeavor of softwareengineering. Design tools include the traditional flowchart, pseudocode,and design specifications document. Additionally, many systemstoday use interactive, visual layout tools. During the codingand debugging phase, a data dictionary and/or class database canbe used to describe and verify relationships and characteristics ofobjects in the program. Once the code is “built,” a version controlsystem keeps track of what was changed, and various automaticdocumentation features can be used to obtain listings of classes,functions, and other program elements.