Clipper 5.x – Drivers Guide
Some of the topics in this guide are intended for advanced Clipper developers. Much of this information is presented at a fairly high level and requires programming knowledge beyond the Clipper language. Other parts are useful to users of all levels. Refer to the “User Interface Levels” section of the Replaceable Database Driver Architecture chapter to determine which part of the language is appropriate to your level of expertise.
Based on your own experience level with the Clipper language, you should decide whether you wish to take advantage of these new and advanced features. The Reference guide contains existing Clipper command and function syntax and descriptions. This guide addresses new extensions to Clipper. Understanding this information should enable you to increase the power and effectiveness of your applications.
Clipper supports a driver architecture that allows Clipper- compiled applications to use replaceable database and terminal drivers. This Drivers guide contains all the information you need to use the replaceable drivers provided as part of the Clipper Development System.
Overview of RDD System
RDD is an abbreviation for Replaceable Database Driver, and it is used to describe an interface that controls how your application accesses and manipulates database and ancillary files.
Clipper provides several RDDs to give you access to the database, memo, and index file formats of many popular database software products. By simply linking the proper RDD with your application, you get automatic, easy access to files created by other database engines.
Moreover, Clipper gives you new and enhanced commands and functions designed to make your applications independent of the RDD in use. Using RDDs, you can give end users more flexibility in choosing to migrate to your Clipper applications without losing data and to easily move their data back and forth between applications if they prefer.
Overview of Alternate Terminal Drivers
An Alternate Terminal Driver is a library file (.LIB) that controls how your application addresses the screen output device. Clipper provides several Alternate Terminal Drivers to allow your applications to run in a wider variety of environments.
Note: To perform normal information presented in screen input/output in a Clipper application, you do not need the Drivers guide. The default database and terminal drivers are automatically linked and the commands and functions used for these purposes are discussed in the Reference guide. For several categorized lists of these commands and functions, refer to Appendix G: Categorized Language Tables in the Error Messages and Appendices guide.
In This Guide
This guide consists of nine chapters including this Introduction chapter.
For an online version of this guide accessible while operating your program editor or any other development utility, use The Guide To Clipper.
Chapter 2: Replaceable Database Driver Architecture
The Clipper database system supports a driver architecture that makes Clipper-compiled applications data format independent. Such applications can, therefore, access the data formats of other database systems, including the dBASE IV (.mdx), FoxPro (.cdx), and Paradox (.db) formats on a variety of equipment. This chapter discusses how RDDs fit into the overall Clipper architecture, defines the basic terminology you will need to understand subsequent chapters, and summarizes new and enhanced commands and functions designed to support the RDD architecture.
Chapter 3: Reference
Clipper 5.x provides many new and enhanced commands and functions that you will use to access and manipulate databases and to get specific information about the RDD in use. This chapter contains entries for all new Clipper commands and functions designed for use with RDDs. As for existing language elements, only those that were changed to accommodate the new RDD architecture are documented here. Other language elements that are specifically designed for database manipulation and have not been altered (e.g., USE) are documented in the Reference guide.
Chapter 4: DBFCDX Driver Installation and Usage
The DBFCDX database driver provides access to FoxPro 2 (.cdx) and (.idx) file formats. This chapter explains how to install DBFCDX and how to use it in your applications.
Chapter 5: DBFMDX Driver Installation and Usage
The DBFMDX database driver provides access to dBASE IV (.dbf), (.mdx), and (.dbt) file formats. The driver also supports dBASE IV-compatible file and record locking schemes, allowing shared access between Clipper and dBASE IV programs. This chapter explains how to install DBFMDX and how to use it in your applications.
Chapter 6: DBFNDX Driver Installation and Usage
The DBFNDX database driver uses the Clipper driver architecture to access dBASE III PLUS compatible index files within a Clipper program, allowing you to create, access, and update dBASE III and dBASE III PLUS compatible index (.ndx) files. This chapter explains how to install DBFNDX and how to use it in your applications.
Chapter 7: DBFNTX Driver Installation and Usage
DBFNTX is the default database driver for Clipper that lets you create and maintain (.ntx) files with features above and beyond those supplied with previous versions of DBFNTX. This chapter details these new features and explains how to install and use DBFNTX in your applications.
Chapter 8: DBPX Driver Installation and Usage
The DBPX database driver provides access to Paradox 3.5 (.db), (.px), (.x) and (.y) file formats. This chapter explains how to install DBPX and how to use it in your applications.
Chapter 9: Alternate Terminal Drivers
Clipper provides several Alternate Terminal Drivers to allow your applications to run in a wider variety of environments. This chapter discusses how Alternate Terminal Drivers fit into the overall Clipper architecture, as well as how to install and use each of the supplied terminal drivers: ANSITERM, NOVTERM, and PCBIOS.