DBase - DBase Programming Language

DBase Programming Language

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.

dBase 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 introduced 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.

In the late 1980s, developer groups sought to create a dBase language standard (IEEE 1192). It was then that the language started being referred to as "xBase" to distinguish it from the Ashton-Tate product. Hundreds of books have been written on dBase and xBase programming.

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 language without the threat of legal action.

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.