dBase

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dBase
DBaseLogo BlackWithRed glass 300.png
Paradigm(s) Imperative, Declarative
Developer C. Wayne Ratliff[1]
Appeared in 1979 (1979)
Influenced Clipper, WordTech products, Harbour. FoxBASE+, FoxPro, Visual FoxPro
Website www.dbase.com

dBase (also stylized dBASE) was one of the first and in its day the most successful database management systems for microcomputers.[2] The dBase system includes the core database engine, a query system, a forms engine, and a programming language that ties all of these components together. dBase's underlying file format, the .dbf file, is widely used in applications needing a simple format to store structured data.

dBase was originally published by Ashton-Tate for microcomputer operating system CP/M in 1980, and later ported to Apple II and IBM PC computers running DOS. On the PC platform, in particular, dBase became one of the best-selling software titles for a number of years. A major upgrade was released as dBase III, and ported to a wider variety of platforms, adding UNIX, and VMS. By the mid-1980s, Ashton-Tate was one of the "big three" software publishers in the early business software market, the others being Lotus Development and WordPerfect.

Starting in the mid-1980s, several companies produced their own variations on the dBase product and especially the dBase programming language. These included FoxBASE+(later renamed FoxPro), Clipper, and other so-called xBase products. Many of these were technically stronger than dBase, but could not push it aside in the market. This changed with the disastrous introduction of dBase IV, whose design and stability were so poor many users switched to other products.[citation needed] At the same time, there was growing use of IBM-invented SQL (Structured Query Language) in database products. Another factor was user adoption of Microsoft Windows on desktop computers. The shift toward SQL and Windows put pressure on the makers of xBase products to invest in major redesign to provide new capabilities.

In spite of growing pressure to evolve, in the early 1990s xBase products constituted the leading database platform for implementing business applications. The size and impact of the xBase market did not go unnoticed, and within one year, the three top xBase firms were acquired by larger software companies. Borland purchased Ashton-Tate, Microsoft bought Fox Software, and Computer Associates acquired Nantucket. However, by the following decade most of the original xBase products had faded from prominence and several disappeared. Products known as dBase still exist, owned by dBase LLC.

History[edit]

Origins[edit]

In the late 1960s, Fred Thompson at the Jet Propulsion Laboratory (JPL) was using a Tymshare product named RETRIEVE to manage a database of electronic calculators, which were at that time very expensive products. In 1971 Fred collaborated with Jack Hatfield, a programmer at JPL, to write an enhanced version of RETRIEVE which became the JPLDIS project. JPLDIS was written in FORTRAN on the UNIVAC 1108 mainframe, and was presented publicly in 1973. When Hatfield left JPL in 1974, Jeb Long took over his role.[3]

While working at JPL as a contractor, C. Wayne Ratliff entered the office football pool. He had no interest in the game, but felt he could win the pool by processing the post-game statistics found in newspapers. In order to do this, he turned his attention to a database system and, by chance, came across the documentation for JPLDIS. He used this as the basis for a port to PTDOS on his kit-built IMSAI 8080 microcomputer, and called the resulting system Vulcan (after Mr. Spock on Star Trek).[4]

Ashton-Tate[edit]

George Tate and Hal Lashlee had built two successful start-up companies - Discount Software was one of the first to sell PC software programs through the mail to consumers, and Software Distributors which was one of the first wholesale distributors of PC software in the world. They entered into an agreement with Ratliff to market Vulcan, and formed Ashton-Tate to do so. Ratliff ported Vulcan from PTDOS to CP/M. Hal Pawluk, who handled marketing for the nascent company, decided to change the name to the more business-like "dBase". Pawluk devised the use of lower case "d" and all-caps "BASE" to create a distinctive name (it is an error to write it any other way). Pawluk suggested calling the new product version two ("II") to suggest it was less buggy than an initial release. dBase II was the result and became a standard CP/M application along with WordStar and SuperCalc.[5]

In 1981, IBM commissioned a port of dBase for the then-in-development PC. The resultant program was one of the initial pieces of software available when the IBM PC went on sale the fall of 1981. dBase was one of a very few "professional" programs on the platform at that time, and became a huge success. The customer base included not only end-users, but an increasing number of "value added resellers", or VARs, who purchased dBase, wrote applications with it, and sold the completed systems to their customers. The May 1983 release of dBase II RunTime further entrenched dBase in the VAR market by allowing the VARs to deploy their products using the lower-cost RunTime system.

The success of dBase created many opportunities for third-parties. Soon, hundreds of companies (ranging from one-person shops to large firms) began offering dBase-related application development, libraries of code to add functionality, applications with source code that could be customized and re-sold, consulting, training, and how-to books. A new company in San Diego (today known as Advisor Media http://www.Advisor.com) premiered a magazine devoted to professional use of dBase, Data Based Advisor. All of these activities fueled the rapid rise of dBase as the leading product of its type.

dBase III[edit]

As platforms and operating systems proliferated in the early 1980s, the company found it difficult to port the assembly language-based dBase to target systems. This led to a re-write of the platform in the C programming language, using automated code conversion tools. The resulting code worked, but was essentially undocumented and inhuman in syntax, a problem that would prove to be serious in the future.[citation needed]

The resulting dBase III was released in May 1984. Although reviewers widely panned its lowered performance, the product was otherwise well reviewed. After a few rapid upgrades the system stabilized and was once again a best-seller throughout the 1980s, and formed the famous "application trio" of PC compatibles (dBase, Lotus 123, and WordPerfect). By the fall of 1984, the company had over 500 employees and was taking in $40 million a year in sales, the vast majority from dBase products.

Recent history[edit]

dBase has evolved into a modern object oriented language that runs on 32 bit Windows. It can be used to build a wide variety of applications including web apps hosted on a Windows server, Windows rich client applications, and middleware applications. dBase can access most modern database engines via ODBC drivers.

dBase features an IDE with a Command Window and Navigator, a just in time compiler, a preprocessor, a virtual machine interpreter, a linker for creating dBase application .exe's, a freely available runtime engine, and numerous two-way GUI design tools including a Form Designer, Report Designer, Menu Designer, Label Designer, Datamodule Designer, SQL Query Designer, and Table Designer. Two-way Tools refers to the ability to switch back and forth between using a GUI design tool and the source code editor. Other tools include a Source Code Editor, a Project Manager that simplifies building and deploying a dBase application, and an integrated Debugger. dBase features structured exception handling and has many built-in classes that can be subclassed via single inheritance. There are visual classes, data classes, and many other supporting classes. Visual classes include Form, SubForm, Notebook, Container, Entryfield, RadioButton, SpinBox, ComboBox, ListBox, PushButton, Image, Grid, ScrollBar, ActiveX, Report, ReportViewer, Text, TextLabel and many others. Database classes include Session, Database, Query, Rowset, Field, StoredProc and Datamodule classes. Other classes include File, String, Math, Array, Date, Exception, Object and others. dBase objects can be dynamically subclassed by adding new properties to them at runtime.

The current version, dBase PLUS 8, was announced[6] on March 19, 2013. The product not only supports the existing BDE connectivity, but it also adds support for ADO and ODBC either through the new ADO approach or with the existing BDE connections. This update of dBase PLUS 8 has been graphically enhanced, has been modernized for continued support on today's more recent operating systems including support for running applications on Microsoft’s Windows 8 and Windows Server 2012 product lines. The product is fully compatible with earlier 32 bit versions of dBase including Visual dBase 7.x and dB2K. It is partly compatible with 16 bit Windows versions (dBase for Windows 5.x and Visual dBase 5.x)[7] and with older DOS versions (dBase II, dBase III, dBase IV, and dBase 5).[8] In May of 2012, dBase introduced a new product to allow users of the DOS based dBase products to continue to use the product on the latest Windows OSs and hardware. The new product was called dbDOS(TM)dbdos[9] The latest dbDOS is called dbDOS(TM) PRO 2 and continues to be enhanced.

dBase / xBase programming language[edit]

For handling data, dBase provided detailed procedural commands and functions to open and traverse records in data files (e.g., USE, SKIP, GO TOP, GO BOTTOM, and GO recno), manipulate field values (REPLACE and STORE), and manipulate text strings (e.g., STR() and SUBSTR()), numbers, and dates. Its ability to simultaneously open and manipulate multiple files containing related data led Ashton-Tate to label dBase a "relational database" although it did not meet the criteria defined by Dr. Edgar F. Codd's relational model; it could more accurately be called an application development language and integrated navigational database management system that is influenced by relational concepts.

The dBase product used a runtime interpreter architecture, which allowed the user to execute commands by typing them in a command line "dot prompt." Upon typing a command or function and pressing the return key, the interpreter would immediately execute or evaluate it. Similarly, program scripts (text files with PRG extensions) ran in the interpreter (with the DO command), where each command and variable was evaluated at runtime. This made dBase programs quick and easy to write and test because programmers didn't have to first compile and link them before running them. (For other languages, these steps were tedious in the days of single- and double-digit megahertz CPUs.) The interpreter also handled automatically and dynamically all memory management (i.e., no preallocating memory and no hexadecimal notation), which more than any other feature made it possible for a business person with no programming experience to develop applications.

Conversely, the ease and simplicity of dBase presented a challenge as its users became more expert and as professional programmers were drawn to it. More complex and more critical applications demanded professional programming features for greater reliability and performance, as well as greater developer productivity.

Over time, Ashton-Tate's competitors introduced so-called clone products and compilers that had more robust programming features such as user-defined functions (UDFs) to supplement the built-in function set, scoped variables for writing routines and functions that were less likely to be affected by external processes, arrays for complex data handling, packaging features for delivering applications as executable files without external runtime interpreters, object-oriented syntax, and interfaces for accessing data in remote database management systems. Ashton-Tate also implemented many of these features with varying degrees of success. Ashton-Tate and its competitors also began to incorporate SQL, the ANSI/ISO standard language for creating, modifying, and retrieving data stored in relational database management systems.

Eventually, it became clear that the dBase world had expanded far beyond Ashton-Tate, which was considered to be retarding innovation, growth and the impact of the technology. A "third-party" community had formed, consisting of Fox Software, Nantucket, Alpha Software, Data Based Advisor Magazine, SBT and other application development firms, and major developer groups. They sought to create a dBase language standard, supported by IEEE committee X3J19 and initiative IEEE 1192. They began using "xBase" to generically refer to the language and database design, to distinguish it from the Ashton-Tate product.

Ashton-Tate was invited to participate, but instead it saw the rise of xBase as an illegal threat to its proprietary technology. In 1988 Ashton-Tate filed suit against Fox Software and Santa Cruz Operation (SCO) for copying dBase's "structure and sequence" in FoxBase+ (SCO marketed XENIX and UNIX versions of the Fox products). In December 1990, U.S. District judge Terry Hatter, Jr. dismissed Ashton-Tate's lawsuit and invalidated Ashton-Tate's copyrights for not disclosing that dBase had been based, in part, on the public domain JPLDIS. In October 1991, while the case was still under appeal, Borland International acquired Ashton-Tate, and as one of the merger's provisions the U.S. Justice Department required Borland to end the lawsuit against Fox and allow other companies to use the dBase/xBase language without the threat of legal action.

By the end of 1992, major software companies raised the stakes by acquiring the leading xBase products. Borland acquired Ashton-Tate's dBase products (and later WordTech's xBase products), Microsoft acquired Fox Software's FoxBASE+ and FoxPro products, and Computer Associates acquired Nantucket's Clipper products. Advisor Media built on its Data Based Advisor magazine by launching FoxPro Advisor and Clipper Advisor (and other) developer magazines and journals, and live conferences for developers. However, a planned dBase Advisor Magazine was aborted due the market failure of dBase IV.

By the year 2000 the xBase market had faded as developers shifted to new database systems and programming languages. Computer Associates (later known as CA) eventually dropped Clipper. Borland restructured and sold dBase. Of the major acquirers, Microsoft stuck with xBase the longest, evolving FoxPro into Visual FoxPro, but the product is no longer offered. In 2006 Advisor Media stopped its last-surviving xBase magazine, FoxPro Advisor. The era of xBase dominance has ended, but there are still xBase products. The dBase product line is now owned by dBase LLC.

Programming examples[edit]

Today, implementations of the dBase language have expanded to include many features targeted for business applications, including object-oriented programming, manipulation of remote and distributed data via SQL, Internet functionality, and interaction with modern devices.

The following example opens an employee table ("empl"), gives every manager who supervises 1 or more employees a 10-percent raise, and then prints the names and salaries.

 USE empl
 REPLACE ALL salary WITH salary * 1.1 FOR supervisors > 0
 LIST ALL fname, lname, salary TO PRINT
 * (comment: reserved words shown in CAPITALS for illustration purposes)

Note how one does not have to keep mentioning the table name. The assumed ("current") table stays the same until told otherwise. This is in contrast to SQL which almost always needs explicit tables. Because of its origins as an interpreted interactive language, dBase used a variety of contextual techniques to reduce the amount of typing needed. This facilitated incremental, interactive development but also made larger-scale modular programming difficult. A tenet of modular programming is that the correct execution of a program module must not be affected by external factors such as the state of memory variables or tables being manipulated in other program modules. Because dBase was not designed with this in mind, developers had to be careful about porting (borrowing) programming code that assumed a certain context and it would make writing larger-scale modular code difficult. Work-area-specific references were still possible using the arrow notation ("B->customer") so that multiple tables could be manipulated at the same time. In addition, if the developer had the foresight to name their tables appropriately, they could clearly refer to a large number of tables open at the same time by notation such as ("employee->salary") and ("vacation->start_date"). Alternatively, the alias command could be appended to the initial opening of a table statement which made referencing a table field unambiguous and simple. For example. one can open a table and assign an alias to it in this fashion, "use EMP alias Employee", and henceforth, refer to table variables as "Employee->Name".

Another notable feature is the re-use of the same clauses for different commands. For example, the FOR clause limits the scope of a given command. (It is somewhat comparable to SQL's WHERE clause). Different commands such as LIST, DELETE, REPLACE, BROWSE, etc. could all accept a FOR clause to limit (filter) the scope of their activity. This simplifies the learning of the language.

dBase was also one of the first business-oriented languages to implement string evaluation.

 i = 2
 myMacro = "i + 10"
 i = &myMacro
 * comment: i now has the value 12

Here the "&" tells the interpreter to evaluate the string stored in "myMacro" as if it were programming code. This is an example of a feature that made dBase programming flexible and dynamic, sometimes called "meta ability" in the profession. This could allow programming expressions to be placed inside tables, somewhat reminiscent of formulas in spreadsheet software.

However, it could also be problematic for pre-compiling and for making programming code secure from hacking. But, dBase tended to be used for custom internal applications for small and medium companies where the lack of protection against copying, as compared to compiled software, was often less of an issue.

Interactivity[edit]

In addition to the dot-prompt, dBase III, III+ and dBase IV came packaged with an ASSIST application to manipulate data and queries, as well as an APPSGEN application which allowed the user to generate applications without resorting to code writing like a 4GL. The dBase IV APPSGEN tool was based largely on portions of an early CP/M product named Personal Pearl.

Niches[edit]

Although the language has fallen out of favor as a primary business language, some find dBase an excellent interactive ad-hoc data manipulation tool. Whereas SQL retrieves data sets from a relational database (RDBMS), with dBase one can more easily manipulate, format, analyze and perform calculations on individual records, strings, numbers, and so on in a step-by-step imperative (procedural) way instead of trying to figure out how to use SQL's declarative operations.

Its granularity of operations is generally smaller than SQL, making it easier to split querying and table processing into easy-to-understand and easy-to-test parts. For example, one could insert a BROWSE operation between the filtering and the aggregation step to study the intermediate table or view (applied filter) before the aggregation step is applied.

As an application development platform, dBase fills a gap between lower level languages such as C, C++, and Java and high-level proprietary 4GLs (fourth generation languages) and purely visual tools, providing relative ease-of-use for business people with less formal programming skill and high productivity for professional developers willing to trade off the low-level control.

dBase remained a popular teaching tool even after sales slowed because the text-oriented commands were easier to present in printed training material than the mouse-oriented competitors. (Mouse-oriented commands were added to the product over time, but the command language remained a popular de facto standard while mousing commands tended to be vendor-specific.)

File formats[edit]

A major legacy of dBase is its .dbf file format, which has been adopted in a number of other applications. For example, the shapefile format developed by ESRI for spatial data in its PC ArcInfo geographic information system, uses .dbf files to store feature attribute data.

Microsoft recommends saving a Microsoft Works database file in the dBase file format so that it can be read by Microsoft Excel.[10]

dBase's database system was one of the first to provide a header section for describing the structure of the data in the file.[citation needed] This meant that the program no longer required advance knowledge of the data structure, but rather could ask the data file how it was structured. There are several variations on the .dbf file structure, and not all dBase-related products and .dbf file structures are compatible.

A second filetype is the .dbt file format for memo fields. While character fields are limited to 254 characters each, a memo field is a 10-byte pointer into a .dbt file which can include a much larger text field. dBase was very limited in its ability to process memo fields, but some other xBase languages such as Clipper treated memo fields as strings just like character fields for all purposes except permanent storage.

dBase uses .ndx files for single indexes, and .mdx (multiple-index) files for holding between 1 and 48 indexes. Some xBase languages include compatibility with .ndx files while others use different file formats such as .ntx used by Clipper and .idx/.cdx used by FoxPro or FlagShip. Later iterations of Clipper included drivers for .ndx, .mdx, .idx and .cdx indexes.

References[edit]

External links[edit]